【Mybatis学习笔记2】实现添加、修改、删除、条件操作、万能map等接口

基于上一篇：https://www.cnblogs.com/yunren/p/14253813.html

本篇内容主要是实现insert、update、delete、带参数传递，以及万能map的几个接口。

我们只需要修改dao下的UserMapper接口，以及对应的UserMapper.xml配置文件里的相关内容：

 

1、添加一个用户

package com.coke.dao;

import com.coke.pojo.User;

import java.util.List;
import java.util.Map;

public interface UserMapper {
// 添加一个用户
    int addUser(User user);

}

<?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">

<!-- namespace要和dao.Mapper的接口名一致 -->
<mapper namespace="com.coke.dao.UserMapper">
    <!--
        id 对应namespace中的方法名
        resultType sql执行的返回值
    -->
    <insert id="addUser" parameterType="com.coke.pojo.User">
        insert into mybatis.user (id,name,pwd) values (#{id},#{name },#{pwd})
    </insert>

</mapper>

package com.coke.dao;

import com.coke.pojo.User;
import com.coke.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

/*
测试类
增、删、改，必须提交事务，也就是sqlSession.commit();
*/

public class UserDaoTest {

    @Test
    public void addUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        mapper.addUser(new User(4,"哈哈","111111"));
// 提交事务
        sqlSession.commit();
        sqlSession.close();
    }
}

 

2.修改一个用户信息（根据id字段修改）

因为sql语句是：update mybatis.user set name=%,pwd=% where id=%;，所以我们还是需要User的三个字段，故参数是User对象

package com.coke.dao;

import com.coke.pojo.User;

import java.util.List;
import java.util.Map;

public interface UserMapper {

    // 更新用户
    int updateUser(User user);

}

<?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">

<!-- namespace要和dao.Mapper的接口名一致 -->
<mapper namespace="com.coke.dao.UserMapper">
    <!--
        id 对应namespace中的方法名
        resultType sql执行的返回值
    -->
    <update id="updateUser" parameterType="com.coke.pojo.User">
        update mybatis.user set name=#{name},pwd=#{pwd}  where id=#{id};
    </update>

</mapper>

package com.coke.dao;

import com.coke.pojo.User;
import com.coke.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class UserDaoTest {

    @Test
    public void updateUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        mapper.updateUser(new User(4,"who","444444"));
        sqlSession.commit();
        sqlSession.close();
    }

}

 

3.删除一个用户（根据id）

package com.coke.dao;

import com.coke.pojo.User;

import java.util.List;
import java.util.Map;

public interface UserMapper {
// 删除用户
    int deleteUser(int id);

}

<?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">

<!-- namespace要和dao.Mapper的接口名一致 -->
<mapper namespace="com.coke.dao.UserMapper">
    <!--
        id 对应namespace中的方法名
        resultType sql执行的返回值
    -->

    <delete id="deleteUser" parameterType="int">
        delete from mybatis.user where id=#{id}
    </delete>

</mapper>

package com.coke.dao;

import com.coke.pojo.User;
import com.coke.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class UserDaoTest {

    @Test
    public void deleteUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        mapper.deleteUser(4);
        sqlSession.commit();
        sqlSession.close();

    }
}

 

4.万能map（实现添加用户）

package com.coke.dao;

import com.coke.pojo.User;

import java.util.List;
import java.util.Map;

public interface UserMapper {

    // 万能map
    int addUser2(Map<String,Object> map);

}

<?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">

<!-- namespace要和dao.Mapper的接口名一致 -->
<mapper namespace="com.coke.dao.UserMapper">
    <!--
        id 对应namespace中的方法名
        resultType sql执行的返回值
    -->

    <insert id="addUser2" parameterType="map">
        insert into mybatis.user (id,name,pwd) values (#{userId},#{userName},#{passWord});
    </insert>
</mapper>

package com.coke.dao;

import com.coke.pojo.User;
import com.coke.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class UserDaoTest {

    @Test
    public void addUser2(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        Map<String,Object> map = new HashMap<String, Object>();
        map.put("userId",5);
        map.put("userName","houzi");
        map.put("passWord","000000");

        mapper.addUser2(map);

        sqlSession.commit();
        sqlSession.close();

    }
}

 

总结：

 1.UserMapper.xml

• namespace，对应dao层mapper名称；
• id，对应namespace里的方法名；
• resultType，对应返回类型，只在select中用到；
• parameterType，参数类型，有一个where条件的，就对应该字段的类型；多个字段时用User。

 

2.UserMapper.java与UserMapper.xml对应关系