mybatis从入门到精通(二) 增删查改

mybatis从入门到精通(二) 增删查改

一丶前言

　　"增删查改"是后台开发的常用操作, 因此, 学习mybatis或者其他orm框架有必要统一学习一下"增删查改".

 

二丶准备开发环境

　　使用"mybatis从入门到精通(一) 入门"准备的开发环境

 

三丶查 -- <select/>

　　UserMapper.java

    User selectUser(@Param("userId") int userId);

 

　　UserMapper.xml

    <select id="selectUser" resultMap="UserMap">
        select * from user where user_id = #{userId}
    </select>

 

　　MybatisTests.java

    @Test
    public void selectTest(){
        // 查询
        User user=userMapper.selectUser(1);
        sqlSession.commit();
        
        System.out.println("name: "+user.getUserName()+", age: "+user.getAge());

        Assert.assertEquals(new Integer(1), user.getUserId());
    }

 

四丶增 -- <insert/>

 　　UserMapper.java

    void insertUser(@Param("user") User user);

 

　　UserMapper.xml

    <insert id="insertUser">
        insert into user(user_id, user_name, age, country) values (#{user.userId}, #{user.userName}, #{user.age}, #{user.country})
    </insert>

 

　　MybatisTests.java

    @Test
    public void insertTest(){
        // 插入
        User user=createTestUser();
        userMapper.insertUser(user);

        sqlSession.commit();  // 需要提交， 数据库才会有数据
        
        User user_=userMapper.selectUser(9);
        Assert.assertEquals(true, user_!=null);
        Assert.assertEquals(new Integer(9), user_.getUserId());
        System.out.println(user_.getUserName());
    }

 

 

五丶改 -- <update/>

 　　UserMapper.java

    void updateUserNameById(@Param("userId") int userId, @Param("userName") String userName);

　　

　　UserMapper.xml

    <update id="updateUserNameById">
        update user set user_name=#{userName} where user_id=#{userId}
    </update>

 

　　MybatisTests.java

    @Test
    public void updateTest(){
        User user=userMapper.selectUser(9);
        if(user==null){
            user=createTestUser();
            userMapper.insertUser(user);

            sqlSession.commit();  // 需要提交， 数据库才会有数据
        }
        
        //修改
        userMapper.updateUserNameById(9, "update_name");
        sqlSession.commit();
        
        User user_=userMapper.selectUser(9);
        Assert.assertEquals("update_name", user_.getUserName());
    }

 

 

六丶删 -- <delete/>

 　　UserMapper.java

    void deleteUserById(@Param("userId") int userId);

 

　　UserMapper.xml

    <update id="deleteUserById">
        delete  from  user where user_id=#{userId}
    </update>

 

 　　MybatisTests.java

    @Test
    public void deleteTest(){
        User user=userMapper.selectUser(9);
        if(user==null){
            user=createTestUser();
            userMapper.insertUser(user);

            sqlSession.commit();  // 需要提交， 数据库才会有数据
        }
        
        
        //删除
        userMapper.deleteUserById(9);
        sqlSession.commit();

        User user_=userMapper.selectUser(9);
        Assert.assertEquals(null, user_);
    }

 

　　完整源码, 点此查看

 

 

 学习资料:

　　mybatis官方文档