MyBatis入门到精通——入门篇
目录
一、什么是 MyBatis？
MyBatis 是一款优秀的持久层框架，它支持自定义 SQL、存储过程以及高级映射。MyBatis 免除了几乎所有的 JDBC 代码以及设置参数和获取结果集的工作。MyBatis 可以通过简单的 XML 或注解来配置和映射原始类型、接口和 Java POJO（Plain Old Java Objects，普通老式 Java 对象）为数据库中的记录。
Mybatis官网文档：https://mybatis.org/mybatis-3/zh/getting-started.html
二、入门案例
（1）创建maven项目
在此之前，需要提前配置好java环境变量和maven环境变量。
（2）引入依赖包
在https://mvnrepository.com/ 搜索添加到pom.xml中
注意：如果使用到lombok需要用IDEA转上lombok插件。
<!--mybatis -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.9</version>
</dependency>
<!--mysql-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.28</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.22</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>（3）创建数据库执行sql脚本
/*
Navicat Premium Data Transfer
Source Server : 本地数据库
Source Server Type : MySQL
Source Server Version : 50733
Source Host : localhost:3306
Source Schema : mybatis-simple
Target Server Type : MySQL
Target Server Version : 50733
File Encoding : 65001
Date: 16/04/2022 23:11:46
*/
SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;
-- ----------------------------
-- Table structure for t_user
-- ----------------------------
DROP TABLE IF EXISTS `t_user`;
CREATE TABLE `t_user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(255) CHARACTER SET utf8 COLLATE utf8_bin NULL DEFAULT NULL,
`password` varchar(255) CHARACTER SET utf8 COLLATE utf8_bin NULL DEFAULT NULL,
PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 3 CHARACTER SET = utf8 COLLATE = utf8_bin ROW_FORMAT = Dynamic;
-- ----------------------------
-- Records of t_user
-- ----------------------------
INSERT INTO `t_user` VALUES (1, 'admin1', '123456');
INSERT INTO `t_user` VALUES (2, 'admin2', '123456');
SET FOREIGN_KEY_CHECKS = 1;
三、入门程序源码
项目目录结构
（1）User.java
package com.mybatis.entity;
import lombok.Data;
import java.io.Serializable;
@Data
public class User implements Serializable {
private Integer id;
private String username;
private String password;
}
（2）UserMapper.java
package com.mybatis.mapper;
import com.mybatis.entity.User;
import java.util.List;
public interface UserMapper {
public List<User> selectUserList();
}
（3）MybatisUtils.java
package com.mybatis.util;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.InputStream;
public class MybatisUtils {
private static SqlSessionFactory sqlSessionFactory;
static {
try {
// 获取sqlSessionFactory对象
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}
public static SqlSession getSqlSession() {
SqlSession sqlSession = sqlSessionFactory.openSession();
return sqlSession;
}
}
（4）UserMapperTest.java
package com.mybatis;
import com.mybatis.entity.User;
import com.mybatis.mapper.UserMapper;
import com.mybatis.util.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.List;
public class UserMapperTest {
@Test
public void test() {
// 第一步: 获得sqlSession对象
SqlSession sqlSession = MybatisUtils.getSqlSession();
// 执行 这个过程就相当于创建一个interface的对象
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> userList = mapper.selectUserList();
userList.forEach(System.out::println);
sqlSession.close();
}
}
（6）UserMapper.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">
<!--namespace=绑定一个对应的Mapper接口-->
<mapper namespace="com.mybatis.mapper.UserMapper">
<!--查询用户列表-->
<select id="selectUserList" resultType="com.mybatis.entity.User">
select * from t_user
</select>
</mapper>
（7）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>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.cj.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis-simple"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
<mappers>
<package name="com.mybatis.mapper"/>
</mappers>
</configuration>
（8）pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.mybatis</groupId>
<artifactId>mybatis-simple</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<!--mybatis -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.9</version>
</dependency>
<!--mysql-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.28</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.22</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
</dependencies>
<properties>
<maven.compiler.source>8</maven.compiler.source>
<maven.compiler.target>8</maven.compiler.target>
</properties>
</project>四、程序单元测试结果
运行UserMapperTest类，输出以下结果，就说明运行成功了。
