Mybatis-mapper-xml-基础

今天学习http://www.mybatis.org/mybatis-3/zh/sqlmap-xml.html。关于mapper.xml的sql语句的使用。

项目路径：https://github.com/chenxing12/l4mybatis

首先，准备环境。

1.创建project

在parent项目上右键，new model->maven->mybatis-mapper.

填充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">
    <parent>
        <artifactId>l4mybatis</artifactId>
        <groupId>com.test</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>
 
    <artifactId>mytatis-mapper</artifactId>
 
    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
        </dependency>
    </dependencies>
 
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>
 
 
</project>

在resources下添加log4j.properties:

log4j.rootLogger=DEBUG, stdout, logfile
 
 
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d %p [%c] - %m%n
 
log4j.appender.logfile=org.apache.log4j.RollingFileAppender
log4j.appender.logfile.File=log/test.log
log4j.appender.logfile.MaxFileSize=128MB
log4j.appender.logfile.MaxBackupIndex=3
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout
log4j.appender.logfile.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p [%t] %c.%M(%L) - %m%n

在resources下添加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>
    <properties resource="db.properties"/>
 
    <typeAliases>
        <package name="com.test.mapper.model"/>
    </typeAliases>
 
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com.test.mapper.mapper/PersonMapper.xml"/>
    </mappers>
</configuration>

在resources下添加db.properties:

#jdbc.driver=com.mysql.jdbc.Driver
jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&serverTimezone=Asia/Shanghai&useSSL=false
jdbc.username=root
jdbc.password=123456

在数据库mybatis中创建一个person表：

/*
Navicat MySQL Data Transfer
 
Source Server         : localhost
Source Server Version : 50605
Source Host           : localhost:3306
Source Database       : mybatis
 
Target Server Type    : MYSQL
Target Server Version : 50605
File Encoding         : 65001
 
Date: 2016-07-06 22:22:34
*/
 
SET FOREIGN_KEY_CHECKS=0;
 
-- ----------------------------
-- Table structure for person
-- ----------------------------
DROP TABLE IF EXISTS `person`;
CREATE TABLE `person` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;
 
-- ----------------------------
-- Records of person
-- ----------------------------
INSERT INTO `person` VALUES ('1', 'Ryan');

在resources下创建com.test.mapper.mapper/PersonMapper.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.test.mapper.dao.PersonMapper">
    <select id="selectPerson" parameterType="int" resultType="hashmap">
        select * from person where id = #{id}
    </select>
 
</mapper>

在java下新建com.test.mapper.dao.PersonMapper.java:

package com.test.mapper.dao;
 
import java.util.HashMap;
 
/**
 * Created by miaorf on 2016/7/6.
 */
public interface PersonMapper {
 
    HashMap selectPerson(int id);
}

在java下添加：com.test.mapper.model.Person:

package com.test.mapper.model;
 
import java.io.Serializable;
 
/**
 * Created by miaorf on 2016/7/6.
 */
public class Person implements Serializable {
 
    private Integer id;
    private String name;
 
    public Integer getId() {
        return id;
    }
 
    public void setId(Integer id) {
        this.id = id;
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    @Override
    public String toString() {
        return "Person{" +
                "id=" + id +
                ", name='" + name + '\'' +
                '}';
    }
}

测试环境：

在test下创建com.test.mapper.dao.PersonMapperTest:

package com.test.mapper.dao;
 
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 org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;
 
import java.io.IOException;
import java.util.HashMap;
 
import static org.junit.Assert.*;
 
/**
 * Created by miaorf on 2016/7/6.
 */
public class PersonMapperTest {
    private SqlSession sqlSession;
    private static SqlSessionFactory sqlSessionFactory;
 
    @BeforeClass
    public static void init() throws IOException {
        String config = "mybatis-config.xml";
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream(config));
    }
 
    @Before
    public void setUp() throws Exception {
        sqlSession = sqlSessionFactory.openSession();
    }
 
    @Test
    public void selectPerson() throws Exception {
        PersonMapper mapper = sqlSession.getMapper(PersonMapper.class);
        HashMap map = mapper.selectPerson(1);
        System.out.println(map);
    }
 
}

运行：

2016-07-06 22:23:31,962 DEBUG [org.apache.ibatis.logging.LogFactory] - Logging initialized using 'class org.apache.ibatis.logging.slf4j.Slf4jImpl' adapter.
2016-07-06 22:23:32,128 DEBUG [org.apache.ibatis.io.VFS] - Class not found: org.jboss.vfs.VFS
2016-07-06 22:23:32,129 DEBUG [org.apache.ibatis.io.JBoss6VFS] - JBoss 6 VFS API is not available in this environment.
2016-07-06 22:23:32,131 DEBUG [org.apache.ibatis.io.VFS] - Class not found: org.jboss.vfs.VirtualFile
2016-07-06 22:23:32,132 DEBUG [org.apache.ibatis.io.VFS] - VFS implementation org.apache.ibatis.io.JBoss6VFS is not valid in this environment.
2016-07-06 22:23:32,134 DEBUG [org.apache.ibatis.io.VFS] - Using VFS adapter org.apache.ibatis.io.DefaultVFS
2016-07-06 22:23:32,135 DEBUG [org.apache.ibatis.io.DefaultVFS] - Find JAR URL: file:/D:/workspace/mybatis/l4mybatis/mytatis-mapper/target/classes/com/test/mapper/model
2016-07-06 22:23:32,135 DEBUG [org.apache.ibatis.io.DefaultVFS] - Not a JAR: file:/D:/workspace/mybatis/l4mybatis/mytatis-mapper/target/classes/com/test/mapper/model
2016-07-06 22:23:32,213 DEBUG [org.apache.ibatis.io.DefaultVFS] - Reader entry: Person.class
2016-07-06 22:23:32,214 DEBUG [org.apache.ibatis.io.DefaultVFS] - Listing file:/D:/workspace/mybatis/l4mybatis/mytatis-mapper/target/classes/com/test/mapper/model
2016-07-06 22:23:32,214 DEBUG [org.apache.ibatis.io.DefaultVFS] - Find JAR URL: file:/D:/workspace/mybatis/l4mybatis/mytatis-mapper/target/classes/com/test/mapper/model/Person.class
2016-07-06 22:23:32,215 DEBUG [org.apache.ibatis.io.DefaultVFS] - Not a JAR: file:/D:/workspace/mybatis/l4mybatis/mytatis-mapper/target/classes/com/test/mapper/model/Person.class
2016-07-06 22:23:32,217 DEBUG [org.apache.ibatis.io.DefaultVFS] - Reader entry: ����   1 6
2016-07-06 22:23:32,220 DEBUG [org.apache.ibatis.io.ResolverUtil] - Checking to see if class com.test.mapper.model.Person matches criteria [is assignable to Object]
2016-07-06 22:23:32,306 DEBUG [org.apache.ibatis.datasource.pooled.PooledDataSource] - PooledDataSource forcefully closed/removed all connections.
2016-07-06 22:23:32,307 DEBUG [org.apache.ibatis.datasource.pooled.PooledDataSource] - PooledDataSource forcefully closed/removed all connections.
2016-07-06 22:23:32,309 DEBUG [org.apache.ibatis.datasource.pooled.PooledDataSource] - PooledDataSource forcefully closed/removed all connections.
2016-07-06 22:23:32,310 DEBUG [org.apache.ibatis.datasource.pooled.PooledDataSource] - PooledDataSource forcefully closed/removed all connections.
2016-07-06 22:23:32,511 DEBUG [org.apache.ibatis.transaction.jdbc.JdbcTransaction] - Opening JDBC Connection
2016-07-06 22:23:32,842 DEBUG [org.apache.ibatis.datasource.pooled.PooledDataSource] - Created connection 733672688.
2016-07-06 22:23:32,842 DEBUG [org.apache.ibatis.transaction.jdbc.JdbcTransaction] - Setting autocommit to false on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@2bbaf4f0]
2016-07-06 22:23:32,847 DEBUG [com.test.mapper.dao.PersonMapper.selectPerson] - ==>  Preparing: select * from person where id = ? 
2016-07-06 22:23:32,911 DEBUG [com.test.mapper.dao.PersonMapper.selectPerson] - ==> Parameters: 1(Integer)
2016-07-06 22:23:32,946 DEBUG [com.test.mapper.dao.PersonMapper.selectPerson] - <==      Total: 1
{name=Ryan, id=1}

2.select

查询语句。负责拼接查询语句并将查询结果映射出来。上例中：

<select id="selectPerson" parameterType="int" resultType="hashmap">
  SELECT * FROM PERSON WHERE ID = #{id}
</select>

这个语句的id为selectPerson,这个就是对应mapper接口中的方法的名字。
parameterType是输入参数类型为int。
resultType表示查询结果映射为HashMap
#{id}是占位符，相当于JDBC中采用PreparedStatement时sql语句中的问号，表示参数名为id的参数值会替换这个位置。

注意到mapper.xml的namespace就是指向所对应的mapper 接口：

1	`<mapper` `namespace="com.test.mapper.dao.PersonMapper">`

在mapper接口中的方法要和mapper.xml中的id所一一对应。因此，这个查询的节点对应的mapper接口的方法为：

public interface PersonMapper {
 
    HashMap selectPerson(int id);
}

事实上，select节点的可选参数有以下几种：

<select
  id="selectPerson"
  parameterType="int"
  parameterMap="deprecated"
  resultType="hashmap"
  resultMap="personResultMap"
  flushCache="false"
  useCache="true"
  timeout="10000"
  fetchSize="256"
  statementType="PREPARED"
  resultSetType="FORWARD_ONLY">

文档对各个参数含义给出了解释：

Select Attributes
属性	描述
`id`	在命名空间中唯一的标识符，可以被用来引用这条语句。
`parameterType`	将会传入这条语句的参数类的完全限定名或别名。这个属性是可选的，因为 MyBatis 可以通过 TypeHandler 推断出具体传入语句的参数，默认值为 unset。
~~parameterMap~~	~~这是引用外部 parameterMap 的已经被废弃的方法。使用内联参数映射和 parameterType 属性。~~
`resultType`	从这条语句中返回的期望类型的类的完全限定名或别名。注意如果是集合情形，那应该是集合可以包含的类型，而不能是集合本身。使用 resultType 或 resultMap，但不能同时使用。
`resultMap`	外部 resultMap 的命名引用。结果集的映射是 MyBatis 最强大的特性，对其有一个很好的理解的话，许多复杂映射的情形都能迎刃而解。使用 resultMap 或 resultType，但不能同时使用。
`flushCache`	将其设置为 true，任何时候只要语句被调用，都会导致本地缓存和二级缓存都会被清空，默认值：false。
`useCache`	将其设置为 true，将会导致本条语句的结果被二级缓存，默认值：对 select 元素为 true。
`timeout`	这个设置是在抛出异常之前，驱动程序等待数据库返回请求结果的秒数。默认值为 unset（依赖驱动）。
`fetchSize`	这是尝试影响驱动程序每次批量返回的结果行数和这个设置值相等。默认值为 unset（依赖驱动）。
`statementType`	STATEMENT，PREPARED 或 CALLABLE 的一个。这会让 MyBatis 分别使用 Statement，PreparedStatement 或 CallableStatement，默认值：PREPARED。
`resultSetType`	FORWARD_ONLY，SCROLL_SENSITIVE 或 SCROLL_INSENSITIVE 中的一个，默认值为 unset （依赖驱动）。
`databaseId`	如果配置了 databaseIdProvider，MyBatis 会加载所有的不带 databaseId 或匹配当前 databaseId 的语句；如果带或者不带的语句都有，则不带的会被忽略。
`resultOrdered`	这个设置仅针对嵌套结果 select 语句适用：如果为 true，就是假设包含了嵌套结果集或是分组了，这样的话当返回一个主结果行的时候，就不会发生有对前面结果集的引用的情况。这就使得在获取嵌套的结果集的时候不至于导致内存不够用。默认值：`false`。
`resultSets`	这个设置仅对多结果集的情况适用，它将列出语句执行后返回的结果集并每个结果集给一个名称，名称是逗号分隔的。

3.Insert

首先，准备数据库：

DROP TABLE IF EXISTS `author`;
CREATE TABLE `author` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(40) NOT NULL DEFAULT '',
  `password` varchar(128) NOT NULL DEFAULT '',
  `email` varchar(40) NOT NULL DEFAULT '',
  `bio` varchar(255) NOT NULL DEFAULT '',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=utf8;

View Code

然后，编写对应实体：com.test.mapper.model.Author

package com.test.mapper.model;
 
import java.io.Serializable;
 
/**
 * Created by miaorf on 2016/7/7.
 */
public class Author implements Serializable {
 
    private Integer id;
    private String username;
    private String password;
    private String email;
    private String bio;
 
    public Author() {
    }
 
    public Author(String username, String password, String email, String bio) {
        this.username = username;
        this.password = password;
        this.email = email;
        this.bio = bio;
    }
 
    public Integer getId() {
        return id;
    }
 
    public void setId(Integer id) {
        this.id = id;
    }
 
    public String getUsername() {
        return username;
    }
 
    public void setUsername(String username) {
        this.username = username;
    }
 
    public String getPassword() {
        return password;
    }
 
    public void setPassword(String password) {
        this.password = password;
    }
 
    public String getEmail() {
        return email;
    }
 
    public void setEmail(String email) {
        this.email = email;
    }
 
    public String getBio() {
        return bio;
    }
 
    public void setBio(String bio) {
        this.bio = bio;
    }
}

编写mapper接口：com.test.mapper.dao.AuthorMapper

package com.test.mapper.dao;
 
import com.test.mapper.model.Author;
 
import java.util.HashMap;
import java.util.List;
 
/**
 * Created by miaorf on 2016/7/6.
 */
public interface AuthorMapper {
 
    int insertAuthor(Author author);
 
    int insertAuthors(List<Author> list);
}