MyBatis_Plus(Spring版本笔记)
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前言
本文主要参考哔站尚硅谷杨博超讲师课件整理而成，属于自己复习使用。
提示：以下是本篇文章正文内容，下面案例可供参考
一、MyBatis-Plus简介
1.1 简介
MyBatis-Plus（简称 MP）是一个 MyBatis的增强工具，在 MyBatis 的基础上只做增强不做改变，为简化开发、提高效率而生。
愿景
我们的愿景是成为 MyBatis 最好的搭档，就像魂斗罗中的 1P、2P，基友搭配，效率翻倍。
1.2 特性
- 无侵入：只做增强不做改变，引入它不会对现有工程产生影响，如丝般顺滑
- 损耗小：启动即会自动注入基本 CURD，性能基本无损耗，直接面向对象操作
- 强大的 CRUD 操作：内置通用 Mapper、通用 Service，仅仅通过少量配置即可实现单表大部分 CRUD 操作，更有强大的条件构造器，满足各类使用需求
- 支持 Lambda 形式调用：通过 Lambda 表达式，方便的编写各类查询条件，无需再担心字段写错
- 支持主键自动生成：支持多达 4 种主键策略（内含分布式唯一 ID 生成器 - Sequence），可自由配置，完美解决主键问题
- 支持 ActiveRecord 模式：支持 ActiveRecord 形式调用，实体类只需继承 Model 类即可进行强大的 CRUD 操作
- 支持自定义全局通用操作：支持全局通用方法注入（ Write once, use anywhere ）
- 内置代码生成器：采用代码或者 Maven 插件可快速生成 Mapper 、 Model 、 Service 、Controller 层代码，支持模板引擎，更有超多自定义配置等您来使用
- 内置分页插件：基于 MyBatis 物理分页，开发者无需关心具体操作，配 插件之后，写分页等同于普通 List 查询
- 分页插件支持多种数据库：支持 MySQL、MariaDB、Oracle、DB2、H2、HSQL、SQLite、Postgre、SQLServer 等多种数据库
- 内置性能分析插件：可输出 SQL 语句以及其执行时间，建议开发测试时启用该功能，能快速揪出慢查询
1.3 支持数据库
任何能使用MyBatis进行 CRUD, 并且支持标准 SQL 的数据库，具体支持情况如下
- MySQL，Oracle，DB2，H2，HSQL，SQLite，PostgreSQLSQLServer，Phoenix，Gauss ，ClickHouse，Sybase，OceanBase，Firebird，Cubrid，Goldilocks，csiidb
- 达梦数据库，虚谷数据库，人大金仓数据库，南大通用(华库)数据库，南大通用数据库，神通数据库，瀚高数据库
1.4 框架结构
1.5 代码及文档地址
官方地址:http://mp.baomidou.com
代码发布地址:
Github: https://github.com/baomidou/mybatis-plus
Gitee: https://gitee.com/baomidou/mybatis-plus
文档发布地址:https://baomidou.com/pages/24112f
二、 入门案例
2.1 开发环境
以maven工程为例，以ssm整合为技术框架。
| 工具 | 版本 |
|---|---|
| IDE | idea 2021.3 |
| JDK | JDK1.8 |
| MAVEN | maven 3.8.4 |
| MySQL | MySQL8.0.25 |
| Spring | 5.3.1 |
| MyBatis-Plus | 3.4.3.4 |
2.2 创建数据库和表
2.2.1 创建表
CREATE DATABASE `mybatis_plus` /*!40100 DEFAULT CHARACTER SET utf8mb4 */; use `mybatis_plus`; CREATE TABLE `user` ( `id` bigint(20) NOT NULL COMMENT '主键ID', `name` varchar(30) DEFAULT NULL COMMENT '姓名', `age` int(11) DEFAULT NULL COMMENT '年龄', `email` varchar(50) DEFAULT NULL COMMENT '邮箱', PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
2.2.2 添加数据
INSERT INTO user (id, name, age, email) VALUES (1, 'Jone', 18, 'test1@baomidou.com'), (2, 'Jack', 20, 'test2@baomidou.com'), (3, 'Tom', 28, 'test3@baomidou.com'), (4, 'Sandy', 21, 'test4@baomidou.com'), (5, 'Billie', 24, 'test5@baomidou.com');
2.3 创建maven工程
2.3.1 打包方式 jar
<packaging>jar</packaging>
2.3.2 引入依赖
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punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>groupId</span><span class="token punctuation">></span></span>com.alibaba<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>groupId</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>artifactId</span><span class="token punctuation">></span></span>druid<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>artifactId</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>version</span><span class="token punctuation">></span></span>1.2.8<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>version</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token 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punctuation">></span></span> <span class="token comment"><!-- 日志 --></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>dependency</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>groupId</span><span class="token punctuation">></span></span>org.slf4j<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>groupId</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>artifactId</span><span class="token punctuation">></span></span>slf4j-api<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>artifactId</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>version</span><span class="token punctuation">></span></span>1.7.30<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>version</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>dependency</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>dependency</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>groupId</span><span class="token punctuation">></span></span>ch.qos.logback<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>groupId</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>artifactId</span><span class="token punctuation">></span></span>logback-classic<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>artifactId</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>version</span><span class="token punctuation">></span></span>1.2.3<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>version</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>dependency</span><span class="token punctuation">></span></span> <span class="token comment"><!-- lombok用来简化实体类 --></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>dependency</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>groupId</span><span class="token punctuation">></span></span>org.projectlombok<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>groupId</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>artifactId</span><span class="token punctuation">></span></span>lombok<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>artifactId</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>version</span><span class="token punctuation">></span></span>1.16.16<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>version</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>dependency</span><span class="token punctuation">></span></span> <span class="token comment"><!--MyBatis-Plus的核心依赖--></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>dependency</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>groupId</span><span class="token punctuation">></span></span>com.baomidou<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>groupId</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>artifactId</span><span class="token punctuation">></span></span>mybatis-plus<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>artifactId</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>version</span><span class="token punctuation">></span></span>3.4.3.4<span class="token tag"><span class="token tag"><span class="token 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class="token punctuation"><</span>groupId</span><span class="token punctuation">></span></span>com.baomidou<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>groupId</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>artifactId</span><span class="token punctuation">></span></span>mybatis-plus-generator<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>artifactId</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>version</span><span class="token punctuation">></span></span>3.5.1<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>version</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token 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punctuation">></span></span>2.3.31<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>version</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>dependency</span><span class="token punctuation">></span></span></dependencies>
<properties>
<spring.version>5.3.1</spring.version>
</properties>
注意：
Spring整合MyBatis，需要MyBatis以及Spring整合MyBatis的依赖：
但是，在以上的依赖列表中，并没有MyBatis以及Spring整合MyBatis的依赖，因为当我们引入了
MyBatis-Plus的依赖时，就可以间接的引入这些依赖
并且依赖和依赖之间的版本必须兼容，所以我们不能随便引入其他版本的依赖，以免发生冲突
在官网上有明确提示：
2.4 Spring整合MyBatis
2.4.1 创建实体
public class User {<span class="token keyword">private</span> <span class="token class-name">Long</span> id<span class="token punctuation">;</span> <span class="token keyword">private</span> <span class="token class-name">String</span> name<span class="token punctuation">;</span> <span class="token keyword">private</span> <span class="token keyword">int</span> age<span class="token punctuation">;</span> <span class="token keyword">private</span> <span class="token class-name">String</span> email<span class="token punctuation">;</span> <span class="token keyword">public</span> <span class="token class-name">User</span><span class="token punctuation">(</span><span class="token class-name">Long</span> id<span class="token punctuation">,</span> <span class="token class-name">String</span> name<span class="token punctuation">,</span> <span class="token keyword">int</span> age<span class="token punctuation">,</span> <span class="token class-name">String</span> email<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token keyword">this</span><span class="token punctuation">.</span>id <span class="token operator">=</span> id<span class="token punctuation">;</span> <span class="token keyword">this</span><span class="token punctuation">.</span>name <span class="token operator">=</span> name<span class="token punctuation">;</span> <span class="token keyword">this</span><span class="token punctuation">.</span>age <span class="token operator">=</span> age<span class="token punctuation">;</span> <span class="token keyword">this</span><span class="token punctuation">.</span>email <span class="token operator">=</span> email<span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token class-name">User</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token class-name">Long</span> <span class="token function">getId</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token keyword">return</span> <span class="token keyword">this</span><span class="token punctuation">.</span>id<span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token class-name">String</span> <span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token keyword">return</span> <span class="token keyword">this</span><span class="token punctuation">.</span>name<span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token keyword">int</span> <span class="token function">getAge</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token keyword">return</span> <span class="token keyword">this</span><span class="token punctuation">.</span>age<span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token class-name">String</span> <span class="token function">getEmail</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token keyword">return</span> <span class="token keyword">this</span><span class="token punctuation">.</span>email<span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token class-name">SexEnum</span> <span class="token function">getSex</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token keyword">return</span> <span class="token keyword">this</span><span class="token punctuation">.</span>sex<span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token keyword">int</span> <span class="token function">getIsDeleted</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token keyword">return</span> <span class="token keyword">this</span><span class="token punctuation">.</span>isDeleted<span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">setId</span><span class="token punctuation">(</span><span class="token class-name">Long</span> id<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token keyword">this</span><span class="token punctuation">.</span>id <span class="token operator">=</span> id<span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">setName</span><span class="token punctuation">(</span><span class="token class-name">String</span> name<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token keyword">this</span><span class="token punctuation">.</span>name <span class="token operator">=</span> name<span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">setAge</span><span class="token punctuation">(</span><span class="token keyword">int</span> age<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token keyword">this</span><span class="token punctuation">.</span>age <span class="token operator">=</span> age<span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">setEmail</span><span class="token punctuation">(</span><span class="token class-name">String</span> email<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token keyword">this</span><span class="token punctuation">.</span>email <span class="token operator">=</span> email<span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">setSex</span><span class="token punctuation">(</span><span class="token class-name">SexEnum</span> sex<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token keyword">this</span><span class="token punctuation">.</span>sex <span class="token operator">=</span> sex<span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">setIsDeleted</span><span class="token punctuation">(</span><span class="token keyword">int</span> isDeleted<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token keyword">this</span><span class="token punctuation">.</span>isDeleted <span class="token operator">=</span> isDeleted<span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token class-name">String</span> <span class="token function">toString</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token keyword">return</span> <span class="token string">"User(id="</span> <span class="token operator">+</span> <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">getId</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">", name="</span> <span class="token operator">+</span> <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">", age="</span> <span class="token operator">+</span> <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">getAge</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">", email="</span> <span class="token operator">+</span> <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">getEmail</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">", sex="</span> <span class="token operator">+</span> <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">getSex</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">", isDeleted="</span> <span class="token operator">+</span> <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">getIsDeleted</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">")"</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
}
2.4.2 创建MyBatis的核心配置文件
在resources下创建mybatis-config.xml
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration></configuration>
2.4.3 创建mapper接口和映射文件
- mapper接口：
public interface TestMapper {
/**
* 查询所有用户信息
* @return
*/
List<User> getAllUser();
}
- mapper映射文件：
在resources下的com/atguigu/mp/mapper目录下创建TestMapper.xml
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.atguigu.mybatisplus.mapper.UserMapper"><span class="token comment"><!--SQL片段，记录基础字段--></span> <span class="token comment"><!--<sql id="BaseColumns">id,name,age,email</sql>--></span> <span class="token comment"><!--第一种写法--></span> <span class="token comment"><!--List<User> getAllUser();--></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>select</span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>getAllUser<span class="token punctuation">"</span></span> <span class="token attr-name">resultType</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>User<span class="token punctuation">"</span></span><span class="token punctuation">></span></span> select <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>include</span> <span class="token attr-name">refid</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>BaseColumns<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>include</span><span class="token punctuation">></span></span> from user <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>select</span><span class="token punctuation">></span></span> <span class="token comment"><!--第二种写法--></span> <span class="token comment"><!--List<User> getAllUser();--></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>select</span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>getAllUser<span class="token punctuation">"</span></span> <span class="token attr-name">resultType</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>User<span class="token punctuation">"</span></span><span class="token punctuation">></span></span> <span class="token comment"><!--select <include refid="BaseColumns"></include> from user--></span> select id,name,age,email from user <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>select</span><span class="token punctuation">></span></span>
</mapper>
2.4.4 创建jdbc.properties
在resources下创建jdbc.properties
jdbc.username=root
jdbc.password=5864@WCY
jdbc.url=jdbc:mysql://localhost:3306/mybatis_plus?useUnicode=true&characterEncoding=utf-8&useSSL=false
jdbc.driver=com.mysql.cj.jdbc.Driver
2.4.5 创建Spring的配置文件
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd"><span class="token comment"><!-- 引入jdbc.properties --></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span><span class="token namespace">context:</span>property-placeholder</span> <span class="token attr-name">location</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>classpath:jdbc.properties<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span><span class="token namespace">context:</span>property-placeholder</span><span class="token punctuation">></span></span> <span class="token comment"><!-- 配置Druid数据源 --></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>bean</span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>dataSource<span class="token punctuation">"</span></span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>com.alibaba.druid.pool.DruidDataSource<span class="token punctuation">"</span></span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>driverClassName<span class="token punctuation">"</span></span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>${jdbc.driver}<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>property</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>url<span class="token punctuation">"</span></span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>${jdbc.url}<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>property</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>username<span class="token punctuation">"</span></span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>${jdbc.username}<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>property</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>password<span class="token punctuation">"</span></span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>${jdbc.password}<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>property</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>bean</span><span class="token punctuation">></span></span> <span class="token comment"><!-- 配置用于创建SqlSessionFactory的工厂bean --></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>bean</span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>mybatisSqlSessionFactoryBean<span class="token punctuation">"</span></span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean<span class="token punctuation">"</span></span><span class="token punctuation">></span></span> <span class="token comment"><!-- 设置MyBatis配置文件的路径（可以不设置） --></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>configLocation<span class="token punctuation">"</span></span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>classpath:mybatis-config.xml<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>property</span><span class="token punctuation">></span></span> <span class="token comment"><!-- 设置数据源 --></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>dataSource<span class="token punctuation">"</span></span> <span class="token attr-name">ref</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>dataSource<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>property</span><span class="token punctuation">></span></span> <span class="token comment"><!-- 设置类型别名所对应的包 --></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>typeAliasesPackage<span class="token punctuation">"</span></span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>com.atguigu.mybatisplus.pojo<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>property</span><span class="token punctuation">></span></span> <span class="token comment"><!-- 设置映射文件的路径 若映射文件所在路径和mapper接口所在路径一致，则不需要设置 --></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>mapperLocations<span class="token punctuation">"</span></span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>classpath:mappers/*Mapper.xml<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>bean</span><span class="token punctuation">></span></span> <span class="token comment"><!-- 配置mapper接口的扫描配置 由mybatis-spring提供，可以将指定包下所有的mapper接口创建动态代理 并将这些动态代理作为IOC容器的bean管理 --></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>bean</span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>mapperScannerConfigurer<span class="token punctuation">"</span></span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>org.mybatis.spring.mapper.MapperScannerConfigurer<span class="token punctuation">"</span></span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>basePackage<span class="token punctuation">"</span></span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>com.atguigu.mybatisplus.mapper<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>property</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>bean</span><span class="token punctuation">></span></span> <span class="token comment"><!--配置自动扫描的包--></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span><span class="token namespace">context:</span>component-scan</span> <span class="token attr-name">base-package</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>com.atguigu.mybatisplus.service<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span><span class="token namespace">context:</span>component-scan</span><span class="token punctuation">></span></span></beans>
2.4.6 添加日志功能
在resources下创建logback.xml
<?xml version="1.0" encoding="UTF-8"?> <configuration debug="false"> <!--定义日志文件的存储地址 logs为当前项目的logs目录 还可以设置为../logs --> <property name="LOG_HOME" value="logs" /><span class="token comment"><!--控制台日志， 控制台输出 --></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>appender</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>STDOUT<span class="token punctuation">"</span></span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>ch.qos.logback.core.ConsoleAppender<span class="token punctuation">"</span></span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>encoder</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>ch.qos.logback.classic.encoder.PatternLayoutEncoder<span class="token punctuation">"</span></span><span class="token punctuation">></span></span> <span class="token comment"><!--格式化输出：%d表示日期，%thread表示线程名，%-5level：级别从左显示5个字符 宽度,%msg：日志消息，%n是换行符--></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>pattern</span><span class="token punctuation">></span></span>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{50} - %msg%n<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>pattern</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>encoder</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>appender</span><span class="token punctuation">></span></span> <span class="token comment"><!--myibatis log configure--></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>logger</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>com.apache.ibatis<span class="token punctuation">"</span></span> <span class="token attr-name">level</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>TRACE<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>logger</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>java.sql.Connection<span class="token punctuation">"</span></span> <span class="token attr-name">level</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>DEBUG<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>logger</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>java.sql.Statement<span class="token punctuation">"</span></span> <span class="token attr-name">level</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>DEBUG<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>logger</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>java.sql.PreparedStatement<span class="token punctuation">"</span></span> <span class="token attr-name">level</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>DEBUG<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span> <span class="token comment"><!-- 日志输出级别 --></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>root</span> <span class="token attr-name">level</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>DEBUG<span class="token punctuation">"</span></span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>appender-ref</span> <span class="token attr-name">ref</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>STDOUT<span class="token punctuation">"</span></span> <span class="token punctuation">/></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>root</span><span class="token punctuation">></span></span></configuration>
2.4.7 测试
- 方式一：通过IOC容器
public class MyBatisPlusTest { @Test public void testMyBatis(){ ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml"); TestMapper mapper = ac.getBean(TestMapper.class); mapper.getAllUser().forEach(user -> System.out.println(user)); } }
- 方式二 Spring整合junit
//在Spring的环境中进行测试
@RunWith(SpringJUnit4ClassRunner.class)
//指定Spring的配置文件
@ContextConfiguration("classpath:applicationContext.xml")
public class MyBatisPlusTest {
@Autowired
private TestMapper testMapper;
@Test
public void testMyBatisBySpring(){
testMapper.getAllUser().forEach(user -> System.out.println(user));
}
}
2.5 加入MyBatis-Plus
Spring整合MyBatis
加入MyBatis-Plus之后
<!-- 此处使用的是MybatisSqlSessionFactoryBean --> <!-- 配置用于创建SqlSessionFactory的工厂bean --> <bean id="mybatisSqlSessionFactoryBean" class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean"><span class="token comment"><!-- 设置MyBatis配置文件的路径（可以不设置） --></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>configLocation<span class="token punctuation">"</span></span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>classpath:mybatis-config.xml<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>property</span><span class="token punctuation">></span></span> <span class="token comment"><!-- 设置数据源 --></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>dataSource<span class="token punctuation">"</span></span> <span class="token attr-name">ref</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>dataSource<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>property</span><span class="token punctuation">></span></span> <span class="token comment"><!-- 设置类型别名所对应的包 --></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>typeAliasesPackage<span class="token punctuation">"</span></span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>com.atguigu.mybatisplus.pojo<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>property</span><span class="token punctuation">></span></span> <span class="token comment"><!-- 设置映射文件的路径 若映射文件所在路径和mapper接口所在路径一致，则不需要设置 --></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>mapperLocations<span class="token punctuation">"</span></span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>classpath:mappers/*Mapper.xml<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>bean</span><span class="token punctuation">></span></span>
此处使用的是MybatisSqlSessionFactoryBean
经观察，目前bean中配置的属性和SqlSessionFactoryBean一致
MybatisSqlSessionFactoryBean是在SqlSessionFactoryBean的基础上进行了增强
即具有SqlSessionFactoryBean的基础功能，又具有MyBatis-Plus的扩展配置
具体配置信息地址(https://baomidou.com/pages/56bac0/#%E5%9F%BA%E6%9C%AC%E9%
85%8D%E7%BD%AE)
2.5.1 创建Mapper接口
public interface UserMapper extends BaseMapper<User> { }
BaseMapper是MyBatis-Plus提供的基础mapper接口，泛型为所操作的实体类型，其中包含CRUD的各个方法，我们的mapper继承了BaseMapper之后，就可以直接使用BaseMapper所提供的各种方法，而不需要编写映射文件以及SQL语句，大大的提高了开发效率
2.5.2 测试
@RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration("classpath:applicationContext.xml") public class MyBatisPlusTest {<span class="token comment">/* 没有使用mybatis_plus @Test public void testMyBatis(){ ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml"); UserMapper mapper = ac.getBean(UserMapper.class); mapper.getAllUser().forEach(user -> System.out.println(user)); } */</span> <span class="token annotation punctuation">@Autowired</span> <span class="token keyword">private</span> <span class="token class-name">UserMapper</span> userMapper<span class="token punctuation">;</span> <span class="token comment">/*---------------------------------使用MyBatisPlus之后-------------------------------------*/</span> <span class="token annotation punctuation">@Test</span> <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">testMyBatisPlus</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{<!-- --></span> <span class="token comment">//查询所有用户信息</span> <span class="token comment">// SELECT id,name,age,email FROM user</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>userMapper<span class="token punctuation">.</span><span class="token function">selectList</span><span class="token punctuation">(</span><span class="token keyword">null</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
2.5.3 结果
2.6 总结
在Spring整合MyBatis中加入了MyBatis-Plus后，我们就可以使用MyBatis-Plus所提供的BaseMapper实现CRUD，并不需要编写映射文件以及SQL语句
但是若要自定义SQL语句，仍然可以编写映射文件而不造成任何影响。因为MyBatis-Plus只做增强，而不做改变。
三、基本CRUD
3.1 BaseMapper
MyBatis-Plus中的基本CRUD在内置的BaseMapper中都已得到了实现，我们可以直接使用，接口如下：
/** * Mapper 继承该接口后，无需编写 mapper.xml 文件，即可获得CRUD功能 * <p>这个 Mapper 支持 id 泛型</p> * * @author hubin * @since 2016-01-23 */ public interface BaseMapper<T> extends Mapper<T> {<span class="token comment">/** * 插入一条记录 * * @param entity 实体对象 */</span> <span class="token keyword">int</span> <span class="token function">insert</span><span class="token punctuation">(</span><span class="token class-name">T</span> entity<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * 根据 ID 删除 * * @param id 主键ID */</span> <span class="token keyword">int</span> <span class="token function">deleteById</span><span class="token punctuation">(</span><span class="token class-name">Serializable</span> id<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * 根据实体(ID)删除 * * @param entity 实体对象 * @since 3.4.4 */</span> <span class="token keyword">int</span> <span class="token function">deleteById</span><span class="token punctuation">(</span><span class="token class-name">T</span> entity<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * 根据 columnMap 条件，删除记录 * * @param columnMap 表字段 map 对象 */</span> <span class="token keyword">int</span> <span class="token function">deleteByMap</span><span class="token punctuation">(</span><span class="token annotation punctuation">@Param</span><span class="token punctuation">(</span><span class="token class-name">Constants</span><span class="token punctuation">.</span>COLUMN_MAP<span class="token punctuation">)</span> <span class="token class-name">Map</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">String</span><span class="token punctuation">,</span> <span class="token class-name">Object</span><span class="token punctuation">></span></span> columnMap<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * 根据 entity 条件，删除记录 * * @param queryWrapper 实体对象封装操作类（可以为 null,里面的 entity 用于生成 where 语句） */</span> <span class="token keyword">int</span> <span class="token function">delete</span><span class="token punctuation">(</span><span class="token annotation punctuation">@Param</span><span class="token punctuation">(</span><span class="token class-name">Constants</span><span class="token punctuation">.</span>WRAPPER<span class="token punctuation">)</span> <span class="token class-name">Wrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">T</span><span class="token punctuation">></span></span> queryWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * 删除（根据ID 批量删除） * * @param idList 主键ID列表(不能为 null 以及 empty) */</span> <span class="token keyword">int</span> <span class="token function">deleteBatchIds</span><span class="token punctuation">(</span><span class="token annotation punctuation">@Param</span><span class="token punctuation">(</span><span class="token class-name">Constants</span><span class="token punctuation">.</span>COLLECTION<span class="token punctuation">)</span> <span class="token class-name">Collection</span><span class="token generics"><span class="token punctuation"><</span><span class="token operator">?</span> <span class="token keyword">extends</span> <span class="token class-name">Serializable</span><span class="token punctuation">></span></span> idList<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * 根据 ID 修改 * * @param entity 实体对象 */</span> <span class="token keyword">int</span> <span class="token function">updateById</span><span class="token punctuation">(</span><span class="token annotation punctuation">@Param</span><span class="token punctuation">(</span><span class="token class-name">Constants</span><span class="token punctuation">.</span>ENTITY<span class="token punctuation">)</span> <span class="token class-name">T</span> entity<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * 根据 whereEntity 条件，更新记录 * * @param entity 实体对象 (set 条件值,可以为 null) * @param updateWrapper 实体对象封装操作类（可以为 null,里面的 entity 用于生成 where 语句） */</span> <span class="token keyword">int</span> <span class="token function">update</span><span class="token punctuation">(</span><span class="token annotation punctuation">@Param</span><span class="token punctuation">(</span><span class="token class-name">Constants</span><span class="token punctuation">.</span>ENTITY<span class="token punctuation">)</span> <span class="token class-name">T</span> entity<span class="token punctuation">,</span> <span class="token annotation punctuation">@Param</span><span class="token punctuation">(</span><span class="token class-name">Constants</span><span class="token punctuation">.</span>WRAPPER<span class="token punctuation">)</span> <span class="token class-name">Wrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">T</span><span class="token punctuation">></span></span> updateWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * 根据 ID 查询 * * @param id 主键ID */</span> <span class="token class-name">T</span> <span class="token function">selectById</span><span class="token punctuation">(</span><span class="token class-name">Serializable</span> id<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * 查询（根据ID 批量查询） * * @param idList 主键ID列表(不能为 null 以及 empty) */</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">T</span><span class="token punctuation">></span></span> <span class="token function">selectBatchIds</span><span class="token punctuation">(</span><span class="token annotation punctuation">@Param</span><span class="token punctuation">(</span><span class="token class-name">Constants</span><span class="token punctuation">.</span>COLLECTION<span class="token punctuation">)</span> <span class="token class-name">Collection</span><span class="token generics"><span class="token punctuation"><</span><span class="token operator">?</span> <span class="token keyword">extends</span> <span class="token class-name">Serializable</span><span class="token punctuation">></span></span> idList<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * 查询（根据 columnMap 条件） * * @param columnMap 表字段 map 对象 */</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">T</span><span class="token punctuation">></span></span> <span class="token function">selectByMap</span><span class="token punctuation">(</span><span class="token annotation punctuation">@Param</span><span class="token punctuation">(</span><span class="token class-name">Constants</span><span class="token punctuation">.</span>COLUMN_MAP<span class="token punctuation">)</span> <span class="token class-name">Map</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">String</span><span class="token punctuation">,</span> <span class="token class-name">Object</span><span class="token punctuation">></span></span> columnMap<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * 根据 entity 条件，查询一条记录 * <p>查询一条记录，例如 qw.last("limit 1") 限制取一条记录, 注意：多条数据会报异常</p> * * @param queryWrapper 实体对象封装操作类（可以为 null） */</span> <span class="token keyword">default</span> <span class="token class-name">T</span> <span class="token function">selectOne</span><span class="token punctuation">(</span><span class="token annotation punctuation">@Param</span><span class="token punctuation">(</span><span class="token class-name">Constants</span><span class="token punctuation">.</span>WRAPPER<span class="token punctuation">)</span> <span class="token class-name">Wrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">T</span><span class="token punctuation">></span></span> queryWrapper<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">T</span><span class="token punctuation">></span></span> ts <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">selectList</span><span class="token punctuation">(</span>queryWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token class-name">CollectionUtils</span><span class="token punctuation">.</span><span class="token function">isNotEmpty</span><span class="token punctuation">(</span>ts<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token keyword">if</span> <span class="token punctuation">(</span>ts<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">!=</span> <span class="token number">1</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token keyword">throw</span> <span class="token class-name">ExceptionUtils</span><span class="token punctuation">.</span><span class="token function">mpe</span><span class="token punctuation">(</span><span class="token string">"One record is expected, but the query result is multiple records"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">return</span> ts<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">return</span> <span class="token keyword">null</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token comment">/** * 根据 Wrapper 条件，查询总记录数 * * @param queryWrapper 实体对象封装操作类（可以为 null） */</span> <span class="token class-name">Long</span> <span class="token function">selectCount</span><span class="token punctuation">(</span><span class="token annotation punctuation">@Param</span><span class="token punctuation">(</span><span class="token class-name">Constants</span><span class="token punctuation">.</span>WRAPPER<span class="token punctuation">)</span> <span class="token class-name">Wrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">T</span><span class="token punctuation">></span></span> queryWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * 根据 entity 条件，查询全部记录 * * @param queryWrapper 实体对象封装操作类（可以为 null） */</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">T</span><span class="token punctuation">></span></span> <span class="token function">selectList</span><span class="token punctuation">(</span><span class="token annotation punctuation">@Param</span><span class="token punctuation">(</span><span class="token class-name">Constants</span><span class="token punctuation">.</span>WRAPPER<span class="token punctuation">)</span> <span class="token class-name">Wrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">T</span><span class="token punctuation">></span></span> queryWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * 根据 Wrapper 条件，查询全部记录 * * @param queryWrapper 实体对象封装操作类（可以为 null） */</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">Map</span><span class="token punctuation"><</span><span class="token class-name">String</span><span class="token punctuation">,</span> <span class="token class-name">Object</span><span class="token punctuation">></span><span class="token punctuation">></span></span> <span class="token function">selectMaps</span><span class="token punctuation">(</span><span class="token annotation punctuation">@Param</span><span class="token punctuation">(</span><span class="token class-name">Constants</span><span class="token punctuation">.</span>WRAPPER<span class="token punctuation">)</span> <span class="token class-name">Wrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">T</span><span class="token punctuation">></span></span> queryWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * 根据 Wrapper 条件，查询全部记录 * <p>注意： 只返回第一个字段的值</p> * * @param queryWrapper 实体对象封装操作类（可以为 null） */</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">Object</span><span class="token punctuation">></span></span> <span class="token function">selectObjs</span><span class="token punctuation">(</span><span class="token annotation punctuation">@Param</span><span class="token punctuation">(</span><span class="token class-name">Constants</span><span class="token punctuation">.</span>WRAPPER<span class="token punctuation">)</span> <span class="token class-name">Wrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">T</span><span class="token punctuation">></span></span> queryWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * 根据 entity 条件，查询全部记录（并翻页） * * @param page 分页查询条件（可以为 RowBounds.DEFAULT） * @param queryWrapper 实体对象封装操作类（可以为 null） */</span> <span class="token generics"><span class="token punctuation"><</span><span class="token class-name">P</span> <span class="token keyword">extends</span> <span class="token class-name">IPage</span><span class="token punctuation"><</span><span class="token class-name">T</span><span class="token punctuation">></span><span class="token punctuation">></span></span> <span class="token class-name">P</span> <span class="token function">selectPage</span><span class="token punctuation">(</span><span class="token class-name">P</span> page<span class="token punctuation">,</span> <span class="token annotation punctuation">@Param</span><span class="token punctuation">(</span><span class="token class-name">Constants</span><span class="token punctuation">.</span>WRAPPER<span class="token punctuation">)</span> <span class="token class-name">Wrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">T</span><span class="token punctuation">></span></span> queryWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * 根据 Wrapper 条件，查询全部记录（并翻页） * * @param page 分页查询条件 * @param queryWrapper 实体对象封装操作类 */</span> <span class="token generics"><span class="token punctuation"><</span><span class="token class-name">P</span> <span class="token keyword">extends</span> <span class="token class-name">IPage</span><span class="token punctuation"><</span><span class="token class-name">Map</span><span class="token punctuation"><</span><span class="token class-name">String</span><span class="token punctuation">,</span> <span class="token class-name">Object</span><span class="token punctuation">></span><span class="token punctuation">></span><span class="token punctuation">></span></span> <span class="token class-name">P</span> <span class="token function">selectMapsPage</span><span class="token punctuation">(</span><span class="token class-name">P</span> page<span class="token punctuation">,</span> <span class="token annotation punctuation">@Param</span><span class="token punctuation">(</span><span class="token class-name">Constants</span><span class="token punctuation">.</span>WRAPPER<span class="token punctuation">)</span> <span class="token class-name">Wrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">T</span><span class="token punctuation">></span></span> queryWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span>}
3.2 BaseMapper功能测试
//插入 @Test public void testInsert(){ // INSERT INTO user ( id, name, age, email ) VALUES ( ?, ?, ?, ? ) User user = new User(6,"张三",23,"zhangsan@126.com");<span class="token keyword">int</span> result <span class="token operator">=</span> userMapper<span class="token punctuation">.</span><span class="token function">insert</span><span class="token punctuation">(</span>user<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"result="</span><span class="token operator">+</span>result<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token comment">//删除</span> <span class="token annotation punctuation">@Test</span> <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">testDelete</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{<!-- --></span> <span class="token comment">//根据Id删除用户</span> <span class="token comment">//DELETE FROM user WHERE id=?</span> <span class="token keyword">int</span> result <span class="token operator">=</span> userMapper<span class="token punctuation">.</span><span class="token function">deleteById</span><span class="token punctuation">(</span><span class="token number">2L</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//根据map集合删除</span> <span class="token comment">//DELETE FROM user WHERE name = ? AND age = ?</span> <span class="token class-name">Map</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">String</span><span class="token punctuation">,</span><span class="token class-name">Object</span><span class="token punctuation">></span></span> map <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">HashMap</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> map<span class="token punctuation">.</span><span class="token function">put</span><span class="token punctuation">(</span><span class="token string">"name"</span><span class="token punctuation">,</span><span class="token string">"张三"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> map<span class="token punctuation">.</span><span class="token function">put</span><span class="token punctuation">(</span><span class="token string">"age"</span><span class="token punctuation">,</span><span class="token number">23</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">int</span> result <span class="token operator">=</span> userMapper<span class="token punctuation">.</span><span class="token function">deleteByMap</span><span class="token punctuation">(</span>map<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 根据id批量删除</span> <span class="token comment">// DELETE FROM user WHERE id IN ( ? , ? , ? )</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">Integer</span><span class="token punctuation">></span></span> list <span class="token operator">=</span> <span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">asList</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">int</span> result <span class="token operator">=</span> userMapper<span class="token punctuation">.</span><span class="token function">deleteBatchIds</span><span class="token punctuation">(</span>list<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"result="</span><span class="token operator">+</span>result<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token comment">//修改</span> <span class="token annotation punctuation">@Test</span> <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">testUpdate</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{<!-- --></span>// UPDATE user SET name=?, email=? WHERE id=?
User user = new User();
user.setId(4L);
user.setName("李四");
user.setEmail("lisi@atguigu.com");
int result = userMapper.updateById(user);
System.out.println("result="+result);
}<span class="token comment">//查询</span> <span class="token annotation punctuation">@Test</span> <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">testSelect</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{<!-- --></span> <span class="token comment">//根据Id查询用户</span>// SELECT id,name,age,email FROM user WHERE id=?
User user = userMapper.selectById(5L);
System.out.println(user);// SELECT id,name,age,email FROM user WHERE id IN ( ? , ? , ? )
List<Integer> list = Arrays.asList(1, 2, 4);
List<User> users = userMapper.selectBatchIds(list);
users.forEach(System.out::println);<span class="token class-name">Map</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">String</span><span class="token punctuation">,</span><span class="token class-name">Object</span><span class="token punctuation">></span></span> map <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">HashMap</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> map<span class="token punctuation">.</span><span class="token function">put</span><span class="token punctuation">(</span><span class="token string">"age"</span><span class="token punctuation">,</span><span class="token number">23</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> users <span class="token operator">=</span> userMapper<span class="token punctuation">.</span><span class="token function">selectByMap</span><span class="token punctuation">(</span>map<span class="token punctuation">)</span><span class="token punctuation">;</span> users<span class="token punctuation">.</span><span class="token function">forEach</span><span class="token punctuation">(</span><span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token operator">::</span><span class="token function">println</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
通过观察BaseMapper中的方法，大多方法中都有Wrapper类型的形参，此为条件构造器，可针对于SQL语句设置不同的条件，若没有条件，则可以为该形参赋值null，即查询（删除/修改）所有数据
3.3 通用Service
说明:
- 通用 Service CRUD 封装IService接口，进一步封装 CRUD 采用 get 查询单行 remove 删除 list 查询集合 page 分页 , 前缀命名方式区分 Mapper 层避免混淆
- 泛型 T 为任意实体对象
- 建议如果存在自定义通用 Service 方法的可能，请创建自己的 IBaseService 继承Mybatis-Plus 提供的基类
- 官网地址：https://baomidou.com/pages/49cc81/#service-crud-%E6%8E%A5%E5%8F%A3
3.3.1 IService
MyBatis-Plus中有一个接口 IService和其实现类 ServiceImpl，封装了常见的业务层逻辑
详情查看源码IService和ServiceImpl
3.3.2 创建Service接口和实现类
UserService
/** * UserService继承IService模板提供的基础功能 */ public interface UserService extends IService<User> {}
UserServiceImpl
/** * ServiceImpl实现了IService，提供了IService中基础功能的实现 * 若ServiceImpl无法满足业务需求，则可以使用自定的UserService定义方法，并在实现类中实现 */ @Service public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {}
3.3.3 在spring配置文件中设置自动扫描service的包
在applicationContext.xml中添加扫描组件的配置，扫描业务层组件，用于测试
<context:component-scan base-package="com.atguigu.mybatisplus.service.impl"></context:component-scan>
3.3.4 测试查询记录条数和批量添加
//spring测试类写法一 @RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration("classpath:applicationContext.xml") public class MyBatisServiceTest {<span class="token annotation punctuation">@Autowired</span> <span class="token keyword">private</span> <span class="token class-name">UserService</span> userService<span class="token punctuation">;</span> <span class="token annotation punctuation">@Test</span> <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">testCount</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{<!-- --></span> <span class="token comment">//查询总记录条数</span> <span class="token comment">//SELECT COUNT( * ) FROM user</span> <span class="token keyword">long</span> count <span class="token operator">=</span> userService<span class="token punctuation">.</span><span class="token function">count</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"总记录条数"</span> <span class="token operator">+</span> count<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token annotation punctuation">@Test</span> <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">testSaveBatch</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{<!-- --></span> <span class="token comment">//实现新增用户</span> <span class="token class-name">ArrayList</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> list <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ArrayList</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// SQL长度有限制，海量数据插入单条SQL无法实行，</span> <span class="token comment">// 因此MP将批量插入放在了通用Service中实现，而不是通用Mapper</span> <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator"><</span> <span class="token number">100</span> <span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token class-name">User</span> user <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">User</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> user<span class="token punctuation">.</span><span class="token function">setName</span><span class="token punctuation">(</span><span class="token string">"abc"</span><span class="token operator">+</span>i<span class="token punctuation">)</span><span class="token punctuation">;</span> user<span class="token punctuation">.</span><span class="token function">setAge</span><span class="token punctuation">(</span><span class="token number">20</span><span class="token operator">+</span>i<span class="token punctuation">)</span><span class="token punctuation">;</span> list<span class="token punctuation">.</span><span class="token function">add</span><span class="token punctuation">(</span>user<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token comment">//INSERT INTO user ( id, name, age ) VALUES ( ?, ?, ? )</span> <span class="token keyword">boolean</span> b <span class="token operator">=</span> userService<span class="token punctuation">.</span><span class="token function">saveBatch</span><span class="token punctuation">(</span>list<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>b<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>}
错误：
Duplicate entry ‘0’ for key ‘PRIMARY’
原因：发现了是数据库表设计不合理导致的；
因为主键设置不能为空，因此默认是以"0"来进行填充的。因此在数据插入时数据的主键id值被0占据，但由于之前已经有数据了，id为“0”的索引已经被占，在使用就会报这个错误，因此我们只需要对表中的主键“id”设置成自增即可。
纠正：为什么会出现这个问题，是因为在创建实体类的时候id属性的类型写成long了，应该写成Long，不然雪花算法是不会实现的。大小写要注意。
四、常用注解
4.1 @TableName
经过以上的测试，在使用MyBatis-Plus实现基本的CRUD时，我们并没有指定要操作的表，只是在Mapper接口继承BaseMapper时，设置了泛型User，而操作的表为user表:
由此得出结论，MyBatis-Plus在确定操作的表时，由BaseMapper的泛型决定，即实体类型决定，且默认操作的表名和实体类型的类名一致
4.1.1 问题
若实体类类型的类名和要操作的表的表名不一致，会出现什么问题？
我们将表user更名为t_user，测试查询功能
程序抛出异常，Table ‘mybatis_plus.user’ doesn’t exist，因为现在的表名为t_user，而默认操作的表名和实体类型的类名一致，即user表
4.1.2 通过@TableName解决问题
在实体类类型上添加==@TableName(“t_user”)==，标识实体类对应的表，即可成功执行SQL语句。
4.1.3 通过GlobalConfig解决问题
在开发的过程中，我们经常遇到以上的问题，即实体类所对应的表都有固定的前缀，例如t_或tbl_
此时，可以使用MyBatis-Plus提供的全局配置，为实体类所对应的表名设置默认的前缀，那么就不需要在每个实体类上通过@TableName标识实体类对应的表。
在spring配置文件中修改：spring-persist.xml中的sqlsessionfactorybean
<!--使用mybatisplus--> <bean id="mybatisSqlSessionFactoryBean" class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean"> <!--指定mybatis配置文件--> <property name="configLocation" value="classpath:mybatis-config.xml"/> <!--指定mapper.xml--> <property name="mapperLocations" value="classpath:mappers/*Mapper.xml"/> <!--装配数据源--> <property name="dataSource" ref="dataSource"/><span class="token comment"><!--设置mybatisplus的全局配置，即表的前缀--></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>globalConfig<span class="token punctuation">"</span></span> <span class="token attr-name">ref</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>globalConfig<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>property</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>bean</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>bean</span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>globalConfig<span class="token punctuation">"</span></span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>com.baomidou.mybatisplus.core.config.GlobalConfig<span class="token punctuation">"</span></span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>dbConfig<span class="token punctuation">"</span></span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>bean</span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>config<span class="token punctuation">"</span></span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>com.baomidou.mybatisplus.core.config.GlobalConfig$DbConfig<span class="token punctuation">"</span></span><span class="token punctuation">></span></span> <span class="token comment"><!--设置实体类所对应的表的前缀--></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>tablePrefix<span class="token punctuation">"</span></span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>t_<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>property</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>bean</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>property</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>bean</span><span class="token punctuation">></span></span>
4.2 @TableId
经过以上的测试，MyBatis-Plus在实现CRUD时，会默认将id作为主键列，并在插入数据时，默认基于雪花算法的策略生成id。
4.2.1 问题引出
若实体类和表中表示主键的不是id，而是其他字段，例如uid，MyBatis-Plus会自动识别uid为主键列吗？
我们实体类中的属性id改为uid，将表中的字段id也改为uid，测试添加功能程序抛出异常，Field ‘uid’ doesn’t have a default value，说明MyBatis-Plus没有将uid作为主键赋值
4.2.2 通过@TableId解决问题
在实体类中uid属性上通过@TableId将其标识为主键，即可成功执行SQL语句。
4.2.3 @TableId的value属性
若实体类中主键对应的属性为id，而表中表示主键的字段为uid，此时若只在属性id上添加注解@TableId，则抛出异常Unknown column ‘id’ in ‘field list’，即MyBatis-Plus仍然会将id作为表的主键操作，而表中表示主键的是字段uid
此时需要通过@TableId注解的value属性，指定表中的主键字段@TableId(“uid”)或@TableId(value=“uid”)
public class User {<span class="token comment">//将属性所对应的字段指定为主键</span> <span class="token comment">// @TableId注解的value属性用于指定主键的字段</span> <span class="token annotation punctuation">@TableId</span><span class="token punctuation">(</span><span class="token string">"uid"</span><span class="token punctuation">)</span> <span class="token keyword">private</span> <span class="token class-name">Long</span> id<span class="token punctuation">;</span>
4.2.4 @TableId的type属性
type属性用来定义主键策略
[1]临时修改
public class User {<span class="token comment">//将属性所对应的字段指定为主键</span> <span class="token comment">// @TableId注解的value属性用于指定主键的字段</span> <span class="token comment">// @TableId注解的type属性设置主键生成策略</span> <span class="token comment">// @TableId(value = "uid", type = IdType.AUTO)</span> <span class="token annotation punctuation">@TableId</span><span class="token punctuation">(</span><span class="token string">"uid"</span><span class="token punctuation">)</span> <span class="token keyword">private</span> <span class="token class-name">Long</span> id<span class="token punctuation">;</span>
[2] 配置全局配置(全局有效)
在spring-persist.xml中修改。
<bean id="globalConfig" class="com.baomidou.mybatisplus.core.config.GlobalConfig">
<property name="dbConfig">
<bean id="config" class="com.baomidou.mybatisplus.core.config.GlobalConfig$DbConfig">
<!--设置实体类所对应的表的前缀-->
<property name="tablePrefix" value="t_"></property>
<!--设置全局主键策略-->
<property name="idType" value="AUTO"></property>
</bean>
</property>
</bean>
4.2.5 雪花算法
4.3 @TableField
经过以上的测试，我们可以发现，MyBatis-Plus在执行SQL语句时，要保证实体类中的属性名和表中的字段名一致
如果实体类中的属性名和字段名不一致的情况，会出现什么问题呢？
a>情况1
若实体类中的属性使用的是驼峰命名风格，而表中的字段使用的是下划线命名风格
例如实体类属性userName，表中字段user_name
此时MyBatis-Plus会自动将下划线命名风格转化为驼峰命名风格
相当于在MyBatis中配置
b>情况2
若实体类中的属性和表中的字段不满足情况1
例如实体类属性name，表中字段username
此时需要在实体类属性上使用@TableField(“username”)设置属性所对应的字段名
//注意：如果实体类中属性名为:name,表中字段名也要为:name // 在不加@TableField注解的情况下，表中字段为:user_name 代码会报错。 //指定属性对应的字段名 //当实体类中是name,表中所对应的字段名是：user_name,可以使用该注解来实现指定属性对应的字段名 @TableField("user_name") private String name;
4.4 @TableLogic（逻辑删除）
4.4.1 逻辑删除
逻辑删除
物理删除：真实删除，将对应数据从数据库中删除，之后查询不到此条被删除的数据
逻辑删除：假删除，将对应数据中代表是否被删除字段的状态修改为“被删除状态”，之后在数据库中仍旧能看到此条数据记录
使用场景：可以进行数据恢复
4.4.2 实现逻辑删除
-
数据库中创建逻辑删除状态列，设置默认值为0
-
实体类中添加逻辑删除属性
//逻辑删除 @TableLogic private Integer isDeleted;
- 测试
- 测试删除功能，真正执行的是修改
UPDATE t_user SET is_deleted=1 WHERE id=? AND is_deleted=0 - 测试查询功能，被逻辑删除的数据默认不会被查询
SELECT id,username AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0
五、条件构造器和常用接口
5.1 wapper介绍
5.2 QueryWrapper
5.2.1 组装查询条件
@RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration("classpath:applicationContext.xml") public class MyBatisPlusWrapperTest {<span class="token annotation punctuation">@Autowired</span> <span class="token keyword">public</span> <span class="token class-name">UserMapper</span> userMapper<span class="token punctuation">;</span> <span class="token annotation punctuation">@Test</span> <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">test01</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{<!-- --></span> <span class="token comment">//查询用户名包含a，年龄在20到30之间，并且邮箱不为null的用户信息</span> <span class="token class-name">QueryWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> queryWrapper <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">QueryWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (user_name LIKE ? AND age BETWEEN ? AND ? AND email IS NOT NULL)</span> queryWrapper<span class="token punctuation">.</span><span class="token function">like</span><span class="token punctuation">(</span><span class="token string">"user_name"</span><span class="token punctuation">,</span><span class="token string">"a"</span><span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token function">between</span><span class="token punctuation">(</span><span class="token string">"age"</span><span class="token punctuation">,</span><span class="token number">20</span><span class="token punctuation">,</span><span class="token number">30</span><span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token function">isNotNull</span><span class="token punctuation">(</span><span class="token string">"email"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> userList <span class="token operator">=</span> userMapper<span class="token punctuation">.</span><span class="token function">selectList</span><span class="token punctuation">(</span>queryWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> userList<span class="token punctuation">.</span><span class="token function">forEach</span><span class="token punctuation">(</span><span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token operator">::</span><span class="token function">println</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
5.2.2 组装排序条件
@Test public void test02(){<span class="token comment">//按年龄降序查询用户，如果年龄相同则按id升序排列</span> <span class="token comment">//SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 ORDER BY age DESC,uid ASC</span> <span class="token class-name">QueryWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> queryWrapper <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">QueryWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> queryWrapper<span class="token punctuation">.</span><span class="token function">orderByDesc</span><span class="token punctuation">(</span><span class="token string">"age"</span><span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token function">orderByAsc</span><span class="token punctuation">(</span><span class="token string">"uid"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> userList <span class="token operator">=</span> userMapper<span class="token punctuation">.</span><span class="token function">selectList</span><span class="token punctuation">(</span>queryWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> userList<span class="token punctuation">.</span><span class="token function">forEach</span><span class="token punctuation">(</span><span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token operator">::</span><span class="token function">println</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
5.2.3 组装删除条件
@Test public void test03(){ //删除email为空的用户 QueryWrapper<User> queryWrapper = new QueryWrapper<>();<span class="token comment">//UPDATE t_user SET is_deleted=1 WHERE is_deleted=0 AND (email IS NULL)</span> <span class="token comment">//出现这个是因为我们设置了逻辑删除，即删除变成了修改，将状态从0(未删除状态)--->1(已删除状态);</span> queryWrapper<span class="token punctuation">.</span><span class="token function">isNull</span><span class="token punctuation">(</span><span class="token string">"email"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">int</span> result <span class="token operator">=</span> userMapper<span class="token punctuation">.</span><span class="token function">delete</span><span class="token punctuation">(</span>queryWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"受影响的行数 ： "</span> <span class="token operator">+</span> result<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
5.2.4 条件的优先级
/** * update(User entity,Wrapper<User> updateWrapper) * 第一个参数为修改的内容，第二个参数为设置修改的条件 参数1设置修改的字段和值，参数2是查询符合的条件 **/<span class="token annotation punctuation">@Test</span> <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">test04</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{<!-- --></span> <span class="token comment">//条件包装器中条件之间默认是and连接。我们不需要手动设置，但是如果是或，我们需要手动设置or.</span> <span class="token comment">//将（年龄大于20并且用户名中包含有a）或邮箱为null的用户信息修改</span> <span class="token class-name">QueryWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> queryWrapper <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">QueryWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//UPDATE t_user SET user_name=?, age=?, email=? WHERE is_deleted=0 AND (user_name LIKE ? AND age > ? OR email IS NULL)</span> queryWrapper<span class="token punctuation">.</span><span class="token function">like</span><span class="token punctuation">(</span><span class="token string">"user_name"</span><span class="token punctuation">,</span><span class="token string">"a"</span><span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token function">gt</span><span class="token punctuation">(</span><span class="token string">"age"</span><span class="token punctuation">,</span><span class="token number">20</span><span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token function">or</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token function">isNull</span><span class="token punctuation">(</span><span class="token string">"email"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">User</span> user <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">User</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> user<span class="token punctuation">.</span><span class="token function">setName</span><span class="token punctuation">(</span><span class="token string">"小明"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> user<span class="token punctuation">.</span><span class="token function">setEmail</span><span class="token punctuation">(</span><span class="token string">"test@atguigu.com"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">int</span> result <span class="token operator">=</span> userMapper<span class="token punctuation">.</span><span class="token function">update</span><span class="token punctuation">(</span>user<span class="token punctuation">,</span> queryWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"受影响的行数："</span> <span class="token operator">+</span> result<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
@Test
public void test05(){
//将（年龄大于20或邮箱为null）并且用户名中包含有a的用户信息修改
//lambda表达式内的逻辑优先运算
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
//SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (user_name LIKE ? AND (age > ? OR email IS NULL))
queryWrapper.like("user_name","a")
.and(i ->i.gt("age",20).or().isNull("email"));
List<User> userList = userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
5.2.5 组装select子句
@Test public void test06(){ //查询用户信息的username和age字段 QueryWrapper<User> queryWrapper = new QueryWrapper<>();<span class="token comment">//SELECT user_name,age FROM t_user WHERE is_deleted=0</span> queryWrapper<span class="token punctuation">.</span><span class="token function">select</span><span class="token punctuation">(</span><span class="token string">"user_name"</span><span class="token punctuation">,</span><span class="token string">"age"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">Map</span><span class="token punctuation"><</span><span class="token class-name">String</span><span class="token punctuation">,</span> <span class="token class-name">Object</span><span class="token punctuation">></span><span class="token punctuation">></span></span> maps <span class="token operator">=</span> userMapper<span class="token punctuation">.</span><span class="token function">selectMaps</span><span class="token punctuation">(</span>queryWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> maps<span class="token punctuation">.</span><span class="token function">forEach</span><span class="token punctuation">(</span><span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token operator">::</span><span class="token function">println</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
5.2.6 实现子查询
@Test public void test07(){<span class="token comment">//查询id小于等于3的用户信息</span> <span class="token class-name">QueryWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> queryWrapper <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">QueryWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (uid IN (select uid from t_user where uid <= 3))</span> queryWrapper<span class="token punctuation">.</span><span class="token function">inSql</span><span class="token punctuation">(</span><span class="token string">"uid"</span><span class="token punctuation">,</span><span class="token string">"select uid from t_user where uid <= 3"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> userList <span class="token operator">=</span> userMapper<span class="token punctuation">.</span><span class="token function">selectList</span><span class="token punctuation">(</span>queryWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> userList<span class="token punctuation">.</span><span class="token function">forEach</span><span class="token punctuation">(</span><span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token operator">::</span><span class="token function">println</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
5.3 UpdateWrapper
@Test public void test08(){<span class="token comment">//将用户名中包含有a并且（年龄大于20或邮箱为null）的用户信息修改</span> <span class="token comment">// 组装set子句以及修改条件</span> <span class="token class-name">UpdateWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> updateWrapper <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">UpdateWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/*写在一起 updateWrapper.set("age",18) .set("email","user@atguigu.com") .like("user_name","a") .and(i ->i.gt("age",20).or().isNull("email")); */</span> <span class="token comment">//分开写</span> <span class="token comment">//UPDATE t_user SET user_name=?,email=? WHERE is_deleted=0 AND (user_name LIKE ? AND (age > ? OR email IS NULL))</span> updateWrapper<span class="token punctuation">.</span><span class="token function">like</span><span class="token punctuation">(</span><span class="token string">"user_name"</span><span class="token punctuation">,</span><span class="token string">"a"</span><span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token function">and</span><span class="token punctuation">(</span>i <span class="token operator">-></span>i<span class="token punctuation">.</span><span class="token function">gt</span><span class="token punctuation">(</span><span class="token string">"age"</span><span class="token punctuation">,</span><span class="token number">20</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">or</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">isNull</span><span class="token punctuation">(</span><span class="token string">"email"</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> updateWrapper<span class="token punctuation">.</span><span class="token function">set</span><span class="token punctuation">(</span><span class="token string">"user_name"</span><span class="token punctuation">,</span><span class="token string">"小黑"</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">set</span><span class="token punctuation">(</span><span class="token string">"email"</span><span class="token punctuation">,</span><span class="token string">"abc@atguigu.xom"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//这里必须要创建User对象，否则无法应用自动填充。如果没有自动填充，可以设置为null</span> <span class="token comment">//UPDATE t_user SET username=?, age=?,email=? WHERE (username LIKE ? AND(age > ? OR email IS NULL))</span> <span class="token comment">//User user = new User();</span> <span class="token comment">//user.setName("张三");</span> <span class="token comment">//int result = userMapper.update(user, updateWrapper);</span> <span class="token comment">//UPDATE t_user SET age=?,email=? WHERE (username LIKE ? AND (age > ? ORemail IS NULL))</span> <span class="token keyword">int</span> result <span class="token operator">=</span> userMapper<span class="token punctuation">.</span><span class="token function">update</span><span class="token punctuation">(</span><span class="token keyword">null</span><span class="token punctuation">,</span> updateWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"result = "</span> <span class="token operator">+</span> result<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
5.4 condition
在真正开发的过程中，组装条件是常见的功能，而这些条件数据来源于用户输入，是可选的，因此我们在组装这些条件时，必须先判断用户是否选择了这些条件，若选择则需要组装该条件，若没有选择则一定不能组装，以免影响SQL执行的结果。
思路一：
@Test public void test09(){ //定义查询条件，有可能为null（用户未输入或未选择） String username = null; Integer ageBegin = 20; Integer ageEnd = 30;<span class="token class-name">QueryWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> queryWrapper <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">QueryWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (age >= ? AND age <= ?)</span> <span class="token comment">//StringUtils.isNotBlank()判断某字符串是否不为空且长度不为0且不由空白符(whitespace)构成</span> <span class="token keyword">if</span><span class="token punctuation">(</span><span class="token class-name">StringUtils</span><span class="token punctuation">.</span><span class="token function">isNotBlank</span><span class="token punctuation">(</span>username<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">{<!-- --></span> queryWrapper<span class="token punctuation">.</span><span class="token function">like</span><span class="token punctuation">(</span><span class="token string">"user_name"</span><span class="token punctuation">,</span><span class="token string">"a"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">if</span> <span class="token punctuation">(</span>ageBegin <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">)</span><span class="token punctuation">{<!-- --></span> queryWrapper<span class="token punctuation">.</span><span class="token function">ge</span><span class="token punctuation">(</span><span class="token string">"age"</span><span class="token punctuation">,</span>ageBegin<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">if</span> <span class="token punctuation">(</span>ageEnd <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">)</span><span class="token punctuation">{<!-- --></span> queryWrapper<span class="token punctuation">.</span><span class="token function">le</span><span class="token punctuation">(</span><span class="token string">"age"</span><span class="token punctuation">,</span>ageEnd<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> list <span class="token operator">=</span> userMapper<span class="token punctuation">.</span><span class="token function">selectList</span><span class="token punctuation">(</span>queryWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> list<span class="token punctuation">.</span><span class="token function">forEach</span><span class="token punctuation">(</span><span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token operator">::</span><span class="token function">println</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
思路2：
上面的实现方案没有问题，但是代码比较复杂，我们可以使用带condition参数的重载方法构建查询条件，简化代码的编写
@Test public void test10(){ String username = "a"; Integer ageBegin = null; Integer ageEnd = 30;<span class="token class-name">QueryWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> queryWrapper <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">QueryWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (user_name LIKE ? AND age <= ?)</span> queryWrapper<span class="token punctuation">.</span><span class="token function">like</span><span class="token punctuation">(</span><span class="token class-name">StringUtils</span><span class="token punctuation">.</span><span class="token function">isNotBlank</span><span class="token punctuation">(</span>username<span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token string">"user_name"</span><span class="token punctuation">,</span><span class="token string">"a"</span><span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token function">ge</span><span class="token punctuation">(</span>ageBegin <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">,</span><span class="token string">"age"</span><span class="token punctuation">,</span>ageBegin<span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token function">le</span><span class="token punctuation">(</span>ageEnd <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">,</span><span class="token string">"age"</span><span class="token punctuation">,</span>ageEnd<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> list <span class="token operator">=</span> userMapper<span class="token punctuation">.</span><span class="token function">selectList</span><span class="token punctuation">(</span>queryWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> list<span class="token punctuation">.</span><span class="token function">forEach</span><span class="token punctuation">(</span><span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token operator">::</span><span class="token function">println</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
5.5 LambdaQueryWrapper
@Test public void test11(){<span class="token class-name">String</span> username <span class="token operator">=</span> <span class="token string">"a"</span><span class="token punctuation">;</span> <span class="token class-name">Integer</span> ageBegin <span class="token operator">=</span> <span class="token keyword">null</span><span class="token punctuation">;</span> <span class="token class-name">Integer</span> ageEnd <span class="token operator">=</span> <span class="token number">30</span><span class="token punctuation">;</span> <span class="token class-name">LambdaQueryWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> queryWrapper <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">LambdaQueryWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (user_name LIKE ? AND age <= ?)</span> queryWrapper<span class="token punctuation">.</span><span class="token function">like</span><span class="token punctuation">(</span><span class="token class-name">StringUtils</span><span class="token punctuation">.</span><span class="token function">isNotBlank</span><span class="token punctuation">(</span>username<span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token class-name">User</span><span class="token operator">::</span><span class="token function">getName</span><span class="token punctuation">,</span><span class="token string">"a"</span><span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token function">ge</span><span class="token punctuation">(</span>ageBegin <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">,</span><span class="token class-name">User</span><span class="token operator">::</span><span class="token function">getAge</span><span class="token punctuation">,</span>ageBegin<span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token function">le</span><span class="token punctuation">(</span>ageEnd <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">,</span><span class="token class-name">User</span><span class="token operator">::</span><span class="token function">getAge</span><span class="token punctuation">,</span>ageEnd<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> list <span class="token operator">=</span> userMapper<span class="token punctuation">.</span><span class="token function">selectList</span><span class="token punctuation">(</span>queryWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> list<span class="token punctuation">.</span><span class="token function">forEach</span><span class="token punctuation">(</span><span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token operator">::</span><span class="token function">println</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
5.6 LambdaUpdateWrapper
@Test public void test12(){<span class="token comment">//将用户名中包含有a并且（年龄大于20或邮箱为null）的用户信息修改</span> <span class="token comment">// 组装set子句以及修改条件</span> <span class="token class-name">LambdaUpdateWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> updateWrapper <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">LambdaUpdateWrapper</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/*合在一起 updateWrapper .set(User::getAge, 18) .set(User::getEmail, "user@atguigu.com") .like(User::getName, "a") .and(i -> i.lt(User::getAge, 24).or().isNull(User::getEmail)); */</span> <span class="token comment">//分开写</span> updateWrapper<span class="token punctuation">.</span><span class="token function">like</span><span class="token punctuation">(</span><span class="token class-name">User</span><span class="token operator">::</span><span class="token function">getName</span><span class="token punctuation">,</span> <span class="token string">"a"</span><span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token function">and</span><span class="token punctuation">(</span>i <span class="token operator">-></span> i<span class="token punctuation">.</span><span class="token function">lt</span><span class="token punctuation">(</span><span class="token class-name">User</span><span class="token operator">::</span><span class="token function">getAge</span><span class="token punctuation">,</span> <span class="token number">24</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">or</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">isNull</span><span class="token punctuation">(</span><span class="token class-name">User</span><span class="token operator">::</span><span class="token function">getEmail</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> updateWrapper<span class="token punctuation">.</span><span class="token function">set</span><span class="token punctuation">(</span><span class="token class-name">User</span><span class="token operator">::</span><span class="token function">getName</span><span class="token punctuation">,</span><span class="token string">"小黑"</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">set</span><span class="token punctuation">(</span><span class="token class-name">User</span><span class="token operator">::</span><span class="token function">getEmail</span><span class="token punctuation">,</span><span class="token string">"abc@atguigu.com"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">User</span> user <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">User</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">int</span> result <span class="token operator">=</span> userMapper<span class="token punctuation">.</span><span class="token function">update</span><span class="token punctuation">(</span>user<span class="token punctuation">,</span> updateWrapper<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"受影响的行数："</span> <span class="token operator">+</span> result<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
六、插件
6.1 分页插件
MyBatis Plus自带分页插件，只要简单的配置即可实现分页功能。
6.1.1 添加配置
<!--使用mybatisplus--> <bean id="mybatisSqlSessionFactoryBean" class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean"> <!--指定mybatis配置文件--> <property name="configLocation" value="classpath:mybatis-config.xml"/> <!--指定mapper.xml--> <property name="mapperLocations" value="classpath:mappers/*Mapper.xml"/> <!--装配数据源--> <property name="dataSource" ref="dataSource"/> <!--设置mybatisplus的全局配置，即表的前缀--> <property name="globalConfig" ref="globalConfig"></property> <!--配置插件--> <property name="plugins"> <array> <ref bean="mybatisPlusInterceptor"></ref> </array> </property> </bean><span class="token comment"><!--配置MyBatis-Plus插件--></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>bean</span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>mybatisPlusInterceptor<span class="token punctuation">"</span></span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor<span class="token punctuation">"</span></span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>interceptors<span class="token punctuation">"</span></span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>list</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>ref</span> <span class="token attr-name">bean</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>paginationInnerInterceptor<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>ref</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>list</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>property</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>bean</span><span class="token punctuation">></span></span> <span class="token comment"><!--配置Mybatis-plus分页插件的bean--></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>bean</span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>paginationInnerInterceptor<span class="token punctuation">"</span></span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor<span class="token punctuation">"</span></span><span class="token punctuation">></span></span> <span class="token comment"><!--设置数据库类型--></span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>property</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>dbType<span class="token punctuation">"</span></span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>MYSQL<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>property</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>bean</span><span class="token punctuation">></span></span>
6.1.2 测试
@Test public void testPage(){ //设置分页参数 Page<User> page = new Page<>(2,3);userMapper<span class="token punctuation">.</span><span class="token function">selectPage</span><span class="token punctuation">(</span>page<span class="token punctuation">,</span><span class="token keyword">null</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> list <span class="token operator">=</span> page<span class="token punctuation">.</span><span class="token function">getRecords</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> list<span class="token punctuation">.</span><span class="token function">forEach</span><span class="token punctuation">(</span><span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token operator">::</span><span class="token function">println</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"每页显示的条数："</span><span class="token operator">+</span>page<span class="token punctuation">.</span><span class="token function">getSize</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"总记录数："</span><span class="token operator">+</span>page<span class="token punctuation">.</span><span class="token function">getTotal</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"总页数："</span><span class="token operator">+</span>page<span class="token punctuation">.</span><span class="token function">getPages</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span> <span class="token string">"当前页:"</span> <span class="token operator">+</span> page<span class="token punctuation">.</span><span class="token function">getCurrent</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"是否有下一页:"</span> <span class="token operator">+</span> page<span class="token punctuation">.</span><span class="token function">hasNext</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"是否有上一页:"</span> <span class="token operator">+</span> page<span class="token punctuation">.</span><span class="token function">hasPrevious</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
测试结果：
User(id=1, name=Jone, age=18, email=test1@baomidou.com, isDeleted=0) User(id=2,name=Jack, age=20, email=test2@baomidou.com, isDeleted=0) User(id=3, name=Tom,age=28, email=test3@baomidou.com, isDeleted=0) User(id=4, name=Sandy, age=21,email=test4@baomidou.com, isDeleted=0) User(id=5, name=Billie, age=24, email=test5@baomidou.com, isDeleted=0) 当前页：1 每页显示的条数：5 总记录数：17 总页数：4 是否有上一
页：false 是否有下一页：true
6.2 xml自定义分页
6.2.1 UserMapper中定义接口方法
/** * 根据年龄查询用户列表，分页显示 * @param page 分页对象，xml中可以从里面进行取值，传递参数 Page 即自动分页，必须放在第一位 * @param age 年龄 * @return */ IPage<User> selectPageVo(@Param("page") Page<User> page , @Param("age") Integer age);
}
6.2.2 UserMapper.xml中编写SQL
<!--IPage<User> selectPageVo(@Param("page") Page<User> page , @Param("age") Integer age);-->
<select id="selectPageVo" resultType="User">
select uid,user_name,age,email from t_user where age > #{age}
</select>
6.2.3 测试
@Test public void testPageVo(){<span class="token class-name">Page</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> page <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Page</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">//第一页索引为1，不是0</span> userMapper<span class="token punctuation">.</span><span class="token function">selectPageVo</span><span class="token punctuation">(</span>page<span class="token punctuation">,</span><span class="token number">20</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">User</span><span class="token punctuation">></span></span> list <span class="token operator">=</span> page<span class="token punctuation">.</span><span class="token function">getRecords</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> list<span class="token punctuation">.</span><span class="token function">forEach</span><span class="token punctuation">(</span><span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token operator">::</span><span class="token function">println</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"每页显示的条数："</span><span class="token operator">+</span>page<span class="token punctuation">.</span><span class="token function">getSize</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"总记录数："</span><span class="token operator">+</span>page<span class="token punctuation">.</span><span class="token function">getTotal</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"总页数："</span><span class="token operator">+</span>page<span class="token punctuation">.</span><span class="token function">getPages</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span> <span class="token string">"当前页:"</span> <span class="token operator">+</span> page<span class="token punctuation">.</span><span class="token function">getCurrent</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"是否有下一页:"</span> <span class="token operator">+</span> page<span class="token punctuation">.</span><span class="token function">hasNext</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"是否有上一页:"</span> <span class="token operator">+</span> page<span class="token punctuation">.</span><span class="token function">hasPrevious</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
结果：
User(id=3, name=Tom, age=28, email=test3@baomidou.com, isDeleted=null)
User(id=4,name=Sandy, age=21,email=test4@baomidou.com, isDeleted=null) User(id=5, name=Billie,age=24, email=test5@baomidou.com, isDeleted=null) User(id=8,name=ybc1, age=21,email=null, isDeleted=null)
User(id=9, name=ybc2, age=22,email=null, isDeleted=null)
当前页：1 每页显示的条数：5 总记录数：12 总页数：3 是否有上一页：false 是否有下一页：true
6.3 乐观锁
6.3.1 场景
一件商品，成本价是80元，售价是100元。老板先是通知小李，说你去把商品价格增加50元。小李正在玩游戏，耽搁了一个小时。正好一个小时后，老板觉得商品价格增加到150元，价格太高，可能会影响销量。又通知小王，你把商品价格降低30元。
此时，小李和小王同时操作商品后台系统。小李操作的时候，系统先取出商品价格100元；小王也在操作，取出的商品价格也是100元。小李将价格加了50元，并将100+50=150元存入了数据
库；小王将商品减了30元，并将100-30=70元存入了数据库。是的，如果没有锁，小李的操作就完全被小王的覆盖了。
现在商品价格是70元，比成本价低10元。几分钟后，这个商品很快出售了1千多件商品，老板亏1万多。
6.3.2 乐观锁与悲观锁
上面的故事，如果是乐观锁，小王保存价格前，会检查下价格是否被人修改过了。如果被修改过了，则重新取出的被修改后的价格，150元，这样他会将120元存入数据库。
如果是悲观锁，小李取出数据后，小王只能等小李操作完之后，才能对价格进行操作，也会保证最终的价格是120元。
6.3.3 模拟修改冲突
a>数据库中增加商品表
CREATE TABLE t_product ( id BIGINT(20) NOT NULL COMMENT '主键ID', NAME VARCHAR(30) NULL DEFAULT NULL COMMENT '商品名称', price INT(11) DEFAULT 0 COMMENT '价格', VERSION INT(11) DEFAULT 0 COMMENT '乐观锁版本号', PRIMARY KEY (id) );
b>添加数据
INSERT INTO t_product (id, NAME, price) VALUES (1, '外星人笔记本', 100);
c>添加实体
*/@Data public class Product {<span class="token keyword">private</span> <span class="token class-name">Long</span> id<span class="token punctuation">;</span> <span class="token keyword">private</span> <span class="token class-name">String</span> name<span class="token punctuation">;</span> <span class="token keyword">private</span> <span class="token class-name">Integer</span> price<span class="token punctuation">;</span>
}
d>添加mapper
public interface ProductMapper extends BaseMapper<Product> {
}
f>测试
@Test public void testProduct01(){ //小李查询价格 Product productLi = productMapper.selectById(1); System.out.println("小李查询的商品价格：" + productLi.getPrice());<span class="token comment">//小王查询价格</span> <span class="token class-name">Product</span> productWang <span class="token operator">=</span> productMapper<span class="token punctuation">.</span><span class="token function">selectById</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"小王查询的商品价格："</span> <span class="token operator">+</span> productWang<span class="token punctuation">.</span><span class="token function">getPrice</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//小李将商品价格+50</span> productLi<span class="token punctuation">.</span><span class="token function">setPrice</span><span class="token punctuation">(</span>productLi<span class="token punctuation">.</span><span class="token function">getPrice</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">50</span><span class="token punctuation">)</span><span class="token punctuation">;</span> productMapper<span class="token punctuation">.</span><span class="token function">updateById</span><span class="token punctuation">(</span>productLi<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//小王将商品价格-30</span> productWang<span class="token punctuation">.</span><span class="token function">setPrice</span><span class="token punctuation">(</span>productWang<span class="token punctuation">.</span><span class="token function">getPrice</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">-</span> <span class="token number">30</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">int</span> result <span class="token operator">=</span> productMapper<span class="token punctuation">.</span><span class="token function">updateById</span><span class="token punctuation">(</span>productWang<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//老板查询商品价格</span> <span class="token class-name">Product</span> productBoss <span class="token operator">=</span> productMapper<span class="token punctuation">.</span><span class="token function">selectById</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"老板查询的商品价格为："</span> <span class="token operator">+</span> productBoss<span class="token punctuation">.</span><span class="token function">getPrice</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
6.3.4 乐观锁实现流程
数据库中添加version字段
取出记录时，获取当前version
SELECT id,`name`,price,`version` FROM product WHERE id=1
更新时，version + 1，如果where语句中的version版本不对，则更新失败
UPDATE product SET price=price+50, `version`=`version` + 1 WHERE id=1 AND
`version`=1
6.3.5 Mybatis-Plus实现乐观锁
[1]修改实体类
*/@Data public class Product {<span class="token keyword">private</span> <span class="token class-name">Long</span> id<span class="token punctuation">;</span> <span class="token keyword">private</span> <span class="token class-name">String</span> name<span class="token punctuation">;</span> <span class="token keyword">private</span> <span class="token class-name">Integer</span> price<span class="token punctuation">;</span> <span class="token annotation punctuation">@Version</span> <span class="token keyword">private</span> <span class="token class-name">Integer</span> version<span class="token punctuation">;</span>
}
[2]添加乐观锁插件配置
<!--配置MyBatis-Plus插件--> <bean id="mybatisPlusInterceptor" class="com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor"> <property name="interceptors"> <list> <ref bean="paginationInnerInterceptor"></ref><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>ref</span> <span class="token attr-name">bean</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>optimisticLockerInnerInterceptor<span class="token punctuation">"</span></span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>ref</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>list</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>property</span><span class="token punctuation">></span></span> <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>bean</span><span class="token punctuation">></span></span>
<!--配置乐观锁插件-->
<bean id="optimisticLockerInnerInterceptor" class="com.baomidou.mybatisplus.extension.plugins.inner.OptimisticLockerInnerInterceptor">
</bean>
[3] 测试修改冲突
小李查询商品信息：
SELECT id,name,price,version FROM t_product WHERE id=?
小王查询商品信息：
SELECT id,name,price,version FROM t_product WHERE id=?
小李修改商品价格，自动将version+1
UPDATE t_product SET name=?, price=?, version=? WHERE id=? AND version=?
Parameters: 外星人笔记本(String), 150(Integer), 1(Integer), 1(Long), 0(Integer)
小王修改商品价格，此时version已更新，条件不成立，修改失败
UPDATE t_product SET name=?, price=?, version=? WHERE id=? AND version=?
Parameters: 外星人笔记本(String), 70(Integer), 1(Integer), 1(Long), 0(Integer)
最终，小王修改失败，查询价格：150
SELECT id,name,price,version FROM t_product WHERE id=?
[4]优化流程
@Test public void testProduct01(){ //小李查询价格 Product productLi = productMapper.selectById(1);<span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"小李查询的商品价格："</span> <span class="token operator">+</span> productLi<span class="token punctuation">.</span><span class="token function">getPrice</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//小王查询价格</span> <span class="token class-name">Product</span> productWang <span class="token operator">=</span> productMapper<span class="token punctuation">.</span><span class="token function">selectById</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"小王查询的商品价格："</span> <span class="token operator">+</span> productWang<span class="token punctuation">.</span><span class="token function">getPrice</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//小李将商品价格+50</span> productLi<span class="token punctuation">.</span><span class="token function">setPrice</span><span class="token punctuation">(</span>productLi<span class="token punctuation">.</span><span class="token function">getPrice</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">50</span><span class="token punctuation">)</span><span class="token punctuation">;</span> productMapper<span class="token punctuation">.</span><span class="token function">updateById</span><span class="token punctuation">(</span>productLi<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//小王将商品价格-30</span> productWang<span class="token punctuation">.</span><span class="token function">setPrice</span><span class="token punctuation">(</span>productWang<span class="token punctuation">.</span><span class="token function">getPrice</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">-</span> <span class="token number">30</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">int</span> result <span class="token operator">=</span> productMapper<span class="token punctuation">.</span><span class="token function">updateById</span><span class="token punctuation">(</span>productWang<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">if</span> <span class="token punctuation">(</span>result <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">{<!-- --></span> <span class="token comment">//操作失败，重试</span> <span class="token class-name">Product</span> productNew <span class="token operator">=</span> productMapper<span class="token punctuation">.</span><span class="token function">selectById</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span> productNew<span class="token punctuation">.</span><span class="token function">setPrice</span><span class="token punctuation">(</span>productNew<span class="token punctuation">.</span><span class="token function">getPrice</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">-</span> <span class="token number">30</span><span class="token punctuation">)</span><span class="token punctuation">;</span> productMapper<span class="token punctuation">.</span><span class="token function">updateById</span><span class="token punctuation">(</span>productNew<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token comment">//老板查询商品价格</span> <span class="token class-name">Product</span> productBoss <span class="token operator">=</span> productMapper<span class="token punctuation">.</span><span class="token function">selectById</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"老板查询的商品价格为："</span> <span class="token operator">+</span> productBoss<span class="token punctuation">.</span><span class="token function">getPrice</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
七 、通用枚举
表中的有些字段值是固定的，例如性别（男或女），此时我们可以使用MyBatis-Plus的通用枚举来实现。
7.1 数据库添加字段sex
7.2 创建通用枚举
*/@Getter public enum SexEnum {<span class="token function">MALE</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token string">"男"</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">FEMALE</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token string">"女"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token annotation punctuation">@EnumValue</span> <span class="token comment">//将注解所标识的属性的值存储到数据库中</span> <span class="token keyword">private</span> <span class="token class-name">Integer</span> sex<span class="token punctuation">;</span> <span class="token keyword">private</span> <span class="token class-name">String</span> sexName<span class="token punctuation">;</span> <span class="token class-name">SexEnum</span><span class="token punctuation">(</span><span class="token class-name">Integer</span> sex<span class="token punctuation">,</span> <span class="token class-name">String</span> sexName<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token keyword">this</span><span class="token punctuation">.</span>sex <span class="token operator">=</span> sex<span class="token punctuation">;</span> <span class="token keyword">this</span><span class="token punctuation">.</span>sexName <span class="token operator">=</span> sexName<span class="token punctuation">;</span> <span class="token punctuation">}</span>}
7.3 配置扫描通用枚举
<!--使用mybatisplus-->
<bean id="mybatisSqlSessionFactoryBean" class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
<!--指定mybatis配置文件-->
<property name="configLocation" value="classpath:mybatis-config.xml"/>
<!--指定mapper.xml-->
<property name="mapperLocations" value="classpath:mappers/*Mapper.xml"/>
<!--装配数据源-->
<property name="dataSource" ref="dataSource"/>
<!--设置mybatisplus的全局配置，即表的前缀-->
<property name="globalConfig" ref="globalConfig"></property>
<!--配置扫描通用枚举-->
<property name="typeEnumsPackage" value="com.atguigu.mybatisplus.enums"></property>
<!--配置插件-->
<property name="plugins">
<array>
<ref bean="mybatisPlusInterceptor"></ref>
</array>
</property>
</bean>
7.4 测试
@RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration("classpath:applicationContext.xml") public class MyBatisPlusEnumTest {<span class="token annotation punctuation">@Autowired</span> <span class="token keyword">private</span> <span class="token class-name">UserMapper</span> userMapper<span class="token punctuation">;</span> <span class="token annotation punctuation">@Test</span> <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">testSexEnum</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{<!-- --></span> <span class="token class-name">User</span> user <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">User</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> user<span class="token punctuation">.</span><span class="token function">setName</span><span class="token punctuation">(</span><span class="token string">"Enum"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> user<span class="token punctuation">.</span><span class="token function">setAge</span><span class="token punctuation">(</span><span class="token number">20</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//设置性别信息为枚举项，会将@EnumValue注解所标识的属性值存储到数据库</span> <span class="token comment">// INSERT INTO t_user ( user_name, age, sex, is_deleted ) VALUES ( ?, ?, ?, ? )</span> user<span class="token punctuation">.</span><span class="token function">setSex</span><span class="token punctuation">(</span><span class="token class-name">SexEnum</span><span class="token punctuation">.</span>MALE<span class="token punctuation">)</span><span class="token punctuation">;</span> userMapper<span class="token punctuation">.</span><span class="token function">insert</span><span class="token punctuation">(</span>user<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
八、代码生成器
8.1 引入依赖
<!--代码生成器逆向工程依赖-->
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-generator</artifactId>
<version>3.5.1</version>
</dependency>
<!--代码生成器中 freemarker引擎模板需要这个依赖-->
<dependency>
<groupId>org.freemarker</groupId>
<artifactId>freemarker</artifactId>
<version>2.3.31</version>
</dependency>
8.2 快速生成
public class FastAutoGeneratorTest {<span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span> args<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span> <span class="token class-name">FastAutoGenerator</span><span class="token punctuation">.</span><span class="token function">create</span><span class="token punctuation">(</span><span class="token string">"jdbc:mysql://127.0.0.1:3306/mybatis_plus?characterEncoding=utf-8&userSSL=false"</span><span class="token punctuation">,</span> <span class="token string">"root"</span><span class="token punctuation">,</span> <span class="token string">"5864@WCY"</span><span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token function">globalConfig</span><span class="token punctuation">(</span>builder <span class="token operator">-></span> <span class="token punctuation">{<!-- --></span> builder<span class="token punctuation">.</span><span class="token function">author</span><span class="token punctuation">(</span><span class="token string">"atguigu"</span><span class="token punctuation">)</span> <span class="token comment">// 设置作者</span> <span class="token comment">// .enableSwagger() // 开启 swagger 模式</span> <span class="token punctuation">.</span><span class="token function">fileOverride</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token comment">// 覆盖已生成文件</span> <span class="token punctuation">.</span><span class="token function">outputDir</span><span class="token punctuation">(</span><span class="token string">"F://JAVA listen//code//mybatis_plus"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 指定输出目录</span> <span class="token punctuation">}</span><span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token function">packageConfig</span><span class="token punctuation">(</span>builder <span class="token operator">-></span> <span class="token punctuation">{<!-- --></span> builder<span class="token punctuation">.</span><span class="token function">parent</span><span class="token punctuation">(</span><span class="token string">"com.atguigu"</span><span class="token punctuation">)</span> <span class="token comment">// 设置父包名</span> <span class="token punctuation">.</span><span class="token function">moduleName</span><span class="token punctuation">(</span><span class="token string">"mybatisplus"</span><span class="token punctuation">)</span> <span class="token comment">// 设置父包模块名</span> <span class="token punctuation">.</span><span class="token function">pathInfo</span><span class="token punctuation">(</span><span class="token class-name">Collections</span><span class="token punctuation">.</span><span class="token function">singletonMap</span><span class="token punctuation">(</span><span class="token class-name">OutputFile</span><span class="token punctuation">.</span>mapperXml<span class="token punctuation">,</span> <span class="token string">"F://JAVA listen//code//mybatis_plus"</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">// 设置mapperXml生成路径</span> <span class="token punctuation">}</span><span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token function">strategyConfig</span><span class="token punctuation">(</span>builder <span class="token operator">-></span> <span class="token punctuation">{<!-- --></span> builder<span class="token punctuation">.</span><span class="token function">addInclude</span><span class="token punctuation">(</span><span class="token string">"t_user"</span><span class="token punctuation">)</span> <span class="token comment">// 设置需要生成的表名</span> <span class="token punctuation">.</span><span class="token function">addTablePrefix</span><span class="token punctuation">(</span><span class="token string">"t_"</span><span class="token punctuation">,</span> <span class="token string">"c_"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 设置过滤表前缀</span> <span class="token punctuation">}</span><span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token function">templateEngine</span><span class="token punctuation">(</span><span class="token keyword">new</span> <span class="token class-name">FreemarkerTemplateEngine</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token comment">// 使用Freemarker 引擎模板，默认的是Velocity引擎模板</span> <span class="token punctuation">.</span><span class="token function">execute</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>}
九 、MyBatisX插件
MyBatis-Plus为我们提供了强大的mapper和service模板，能够大大的提高开发效率。
但是在真正开发过程中，MyBatis-Plus并不能为我们解决所有问题，例如一些复杂的SQL，多表联查，我们就需要自己去编写代码和SQL语句，我们该如何快速的解决这个问题呢，这个时候可以使用MyBatisX插件。
MyBatisX一款基于 IDEA 的快速开发插件，为效率而生。
MyBatisX插件用法：https://baomidou.com/pages/ba5b24/
9.1 安装插件
安装方法：打开 IDEA，进入 File -> Settings -> Plugins -> Browse Repositories，输入 mybatisx 搜索并安装
9.2 功能
9.2.1 XML跳转
当mapper映射文件和mapper很多的时候，可以快速定位并跳转到对应的类容上。
9.2.2 快速生成代码
[1]首先需要在datasource中进行配置
[2] 选择驱动
[3]可以直接选择旧版本的驱动,或者按提示下载
[4] 登录后选择数据库、表，然后点击右键选择mybatisx。
[5] 表的基本配置
[6] 生成的基本配置
[7]选择好后会自动帮我们生成各种组件
[8]如果我们要自定义查询功能，我们只需要在mapper中写我们的方法名，插件会自动帮助我们补全方法名并且快速生成相对应的sql语句放在mapper映射文件中。
十、总结
mybatsi-plus可以快速帮助我们完成spring和mybatsi的整合及搭建功能。
