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MyBatis Mapper动态代理方式 详解MyBatis开发Dao层的两种方式(Mapper动态代理方式)

谢亚峰 人气:0

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。

需要注意的是,上文提到的config文件夹和sqlmapper文件夹均为资源文件夹(source folder),默认会加载该路径下的文件。希望对大家的学习有所帮助,也希望大家多多支持。

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