Mybatis学习2：实现增删改查操作CRUD

Posted 2021-09-09 Z|Star

环境搭建见本专栏上篇。

查询用户

根据指定id查询用户

1.编写接口

//根据id查询用户
User selectUserById(int id);

2.修改Mapper.xml

    <select id="selectUserById" resultType="com.kuang.pojo.User">
       select * from user where id = #{id}
   </select>

3.编写测试类

    @Test
   public void tsetSelectUserById() {
       SqlSession session = MybatisUtils.getSession(); //获取SqlSession连接
       UserMapper mapper = session.getMapper(UserMapper.class);
       User user = mapper.selectUserById(1);
       System.out.println(user);
       session.close();
   }

添加用户

1.编写接口

    //添加一个用户
    int addUser(User user);

2.修改Mapper.xml

   <insert id="addUser" parameterType="com.kuang.pojo.User">
       insert into user (id,name,pwd) values (#{id},#{name},#{pwd})
   </insert>

3.编写测试类

   @Test
   public void testAddUser() {
       SqlSession session = MybatisUtils.getSession();
       UserMapper mapper = session.getMapper(UserMapper.class);
       User user = new User(5,"王五","zxcvbn");
       int i = mapper.addUser(user);
       System.out.println(i);
       session.commit(); //提交事务,重点!不写的话不会提交到数据库
       session.close();
   }

修改用户

1.编写接口

    //修改一个用户
    int updateUser(User user);

2.修改Mapper.xml

   <update id="updateUser" parameterType="com.kuang.pojo.User">
       update user set name=#{name},pwd=#{pwd} where id = #{id}
   </update>

3.编写测试类

   @Test
   public void testUpdateUser() {
       SqlSession session = MybatisUtils.getSession();
       UserMapper mapper = session.getMapper(UserMapper.class);
       User user = mapper.selectUserById(1);
       user.setPwd("asdfgh");
       int i = mapper.updateUser(user);
       System.out.println(i);
       session.commit(); //提交事务,重点!不写的话不会提交到数据库
       session.close();
   }

删除用户

根据id删除用户

1.编写接口

    //根据id删除用户
    int deleteUser(int id);

2.修改Mapper.xml

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

3.编写测试类

   @Test
   public void testDeleteUser() {
       SqlSession session = MybatisUtils.getSession();
       UserMapper mapper = session.getMapper(UserMapper.class);
       int i = mapper.deleteUser(5);
       System.out.println(i);
       session.commit(); //提交事务,重点!不写的话不会提交到数据库
       session.close();
   }

注：所有的增删改操作都需要提交事务。