详解MyBatis开发Dao层的两种方式（Mapper动态代理方式）

<?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>

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

}

<mappers>
  <mapper resource="UserMapper.xml"/>
</mappers>

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();
  }

}