时间：2020-10-12 19:21:43 | 栏目：JAVA代码 | 点击：次
MyBatis开发原始Dao层请阅读我的上一篇博客：MyBatis开发Dao层的两种方式（原始Dao层开发）
接上一篇博客继续介绍MyBatis开发Dao层的第二种方式：Mapper动态代理方式
Mapper接口开发方法只需要程序员编写Mapper接口（相当于Dao接口），由Mybatis框架根据接口定义创建接口的动态代理对象，代理对象的方法体同上一篇博客中Dao接口实现类方法。
Mapper接口开发需要遵循以下规范：
（1）Mapper.xml文件中的namespace与mapper接口的类路径相同。
（2）Mapper接口方法名和Mapper.xml中定义的每个statement的id相同
（3）Mapper接口方法的输入参数类型和mapper.xml中定义的每个sql 的parameterType的类型相同
（4）Mapper接口方法的输出参数类型和mapper.xml中定义的每个sql的resultType的类型相同
1、定义mapper映射文件UserMapper.xml（内容同User.xml），需要修改namespace的值为 UserMapper接口路径。将UserMapper.xml放在classpath 下sqlmapperr目录下。
<?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.xyfer.mapper.UserMapper">
<!-- 根据id查询用户 -->
<select id="getUserById" parameterType="int" resultType="com.xyfer.po.User">
select * from user where id = #{id}
</select>
<!-- 添加用户 -->
<insert id="insertUser" parameterType="com.xyfer.po.User">
<selectKey keyProperty="id" order="AFTER" resultType="java.lang.Integer">
select LAST_INSERT_ID()
</selectKey>
insert into user(username,birthday,sex,address)
values(#{username},#{birthday},#{sex},#{address})
</insert>
<!-- 修改用户 -->
<update id="updateUser" parameterType="com.xyfer.po.User">
update user set username=#{username},birthday=#{birthday},sex=#{sex},address=#{address}
where id=#{id}
</update>
<!-- 删除用户 -->
<delete id="deleteUserById" parameterType="int">
delete from user where id=#{id}
</delete>
</mapper>
2、UserMapper.java接口文件
package com.xyfer.mapper;
import com.xyfer.po.User;
public interface UserMapper {
public User getUserById(int id); //根据id值查询一个用户
public void insertUser(User user); //新增一个用户
public void updateUser(User user); //修改一个用户
public void deleteUser(int id); //删除一个用户
}
接口定义有如下特点：
（1）UserMapper接口方法名和Mapper.xml中定义的statement的id相同
（2）UserMapper接口方法的输入参数类型和mapper.xml中定义的statement的parameterType的类型相同
（3） UserMapper接口方法的输出参数类型和mapper.xml中定义的statement的resultType的类型相同
3、在SqlMapConfig.xml文件中加载UserMapper.xml文件
<mappers> <mapper resource="UserMapper.xml"/> </mappers>
4、测试
package com.xyfer.mapper;
import static org.junit.Assert.*;
import java.io.InputStream;
import java.util.Date;
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.Test;
import com.xyfer.po.User;
import junit.framework.TestCase;
public class UserMapperTest extends TestCase{
private SqlSessionFactory sqlSessionFactory;
protected void setUp() throws Exception {
SqlSessionFactoryBuilder sessionFactoryBuilder = new SqlSessionFactoryBuilder();
InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
sqlSessionFactory = sessionFactoryBuilder.build(inputStream);
}
@Test
public void testGetUserById() {
//获取sqlsession
SqlSession sqlsession = sqlSessionFactory.openSession();
//获取UserMapper接口代理对象
UserMapper userMapper = sqlsession.getMapper(UserMapper.class);
//调用代理对象方法
User user = userMapper.getUserById(10);
//打印结果
System.out.println(user);
//关闭sqlsession
sqlsession.close();
}
@Test
public void testInsertUser() {
//获取sqlsession
SqlSession sqlsession = sqlSessionFactory.openSession();
//获取UserMapper接口代理对象
UserMapper userMapper = sqlsession.getMapper(UserMapper.class);
//新建一个对象
User user = new User();
user.setUsername("小谢");
user.setSex("男");
user.setBirthday(new Date());
user.setAddress("浙江省杭州市");
//调用代理对象方法
userMapper.insertUser(user);
//关闭sqlsession
sqlsession.close();
}
@Test
public void testUpdateUser() {
//获取sqlsession
SqlSession sqlsession = sqlSessionFactory.openSession();
//获取UserMapper接口代理对象
UserMapper userMapper = sqlsession.getMapper(UserMapper.class);
//新建一个对象
User user = new User();
user.setUsername("小谢");
user.setSex("男");
user.setBirthday(new Date());
user.setAddress("上海市");
//调用代理对象方法
userMapper.updateUser(user);
//关闭sqlsession
sqlsession.close();
}
@Test
public void testDeleteUser() {
//获取sqlsession
SqlSession sqlsession = sqlSessionFactory.openSession();
//获取UserMapper接口代理对象
UserMapper userMapper = sqlsession.getMapper(UserMapper.class);
//调用代理对象方法
userMapper.deleteUser(6);
//关闭sqlsession
sqlsession.close();
}
}
以上步骤，完成mybatis框架以Mapper动态代理方式开发Dao层，并对数据库进行增删改查操作。