本章将通过实例介绍怎样利用 <update> 更新数据库数据。本实例将根据用户ID修改指定用户的name、sex和age信息。Mapper XML 定义如下：
<update id="updateUser">
UPDATE `user` SET
`name`=#{name, jdbcType=VARCHAR},
`sex`=#{sex, jdbcType=VARCHAR},
`age`=#{age, jdbcType=INTEGER}
WHERE `user_id`=#{userId,jdbcType=INTEGER}
</update>（1）MyBatis 配置文件 mybatis-cfg.xml 内容如下：
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<properties resource="database.properties"/>
<environments default="MySqlDatabase" >
<environment id="MySqlDatabase" >
<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/hxstrive/mybatis/update/demo1/UserMapper.xml" />
</mappers>
</configuration>（2）定义 UserMapper.java 接口文件内容如下：
package com.hxstrive.mybatis.update.demo1;
public interface UserMapper {
/**
* 更新用户信息
* @param userBean
* @return
*/
int updateUser(UserBean userBean);
}（3）定义 UserMapper.xml 文件内容如下：
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.hxstrive.mybatis.update.demo1.UserMapper">
<!-- 使用update实现更新数据的操作，注意：其他属性的用法见insert标签 -->
<update id="updateUser">
UPDATE `user` SET
`name`=#{name, jdbcType=VARCHAR},
`sex`=#{sex, jdbcType=VARCHAR},
`age`=#{age, jdbcType=INTEGER}
WHERE `user_id`=#{userId,jdbcType=INTEGER}
</update>
</mapper>（4）客户端代码如下：
package com.hxstrive.mybatis.update.demo1;
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.InputStream;
public class UpdateDemo1 {
public static void main(String[] args) throws Exception {
// 获取 Mapper 对象
String cfgName = "com/hxstrive/mybatis/update/demo1/mybatis-cfg.xml";
InputStream input = Resources.getResourceAsStream(cfgName);
SqlSessionFactoryBuilder factoryBuilder = new SqlSessionFactoryBuilder();
SqlSessionFactory sqlFactory = factoryBuilder.build(input);
SqlSession sqlSession = sqlFactory.openSession(true);
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
UserBean userBean = new UserBean();
userBean.setUserId(1);
userBean.setName("张三");
userBean.setSex("男");
userBean.setAge(30);
int result = userMapper.updateUser(userBean);
System.out.println("result=" + result);
}
}
