Mybatis——CRUD（增删改查）

1.namespace

namespace中的包名要和dao/mapper接口的包名一直

2.select

• id：就是对应的namespace中的方法名

• resultType：Sql语句执行的返回值

• parameterType：传递参数的类型

1.编写接口

//查询全部用户
List<User> getUserList();
​
//根据id查询用户
User getUserById(int id);

2.编写对应的mapper中的sql语句

<select id="getUserList" resultType="com.yl.pojo.User">
    select * from mybatis.user
</select>
<select id="getUserById" parameterType="int" resultType="com.yl.pojo.User">
    select * from mybatis.user where id = #{id}
</select>

3.测试

@Test
public void test(){
    //获得SqlSession对象
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    //方式一，执行
    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    List<User> userList = userMapper.getUserList();
    for (User user : userList) {
        System.out.println(user);
    }
​
    //关闭sqlSession
    sqlSession.close();
}
​
@Test
public void Test2(){
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    User user = userMapper.getUserById(1);
    System.out.println(user);
    sqlSession.close();
​
}

3.insert

1.编写接口

//增加用户
int addUser(User user);

2.编写对应的mapper中的sql语句

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

3.测试

@Test
public void Test3(){
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    int result = userMapper.addUser(new User(4, "赵六", "123456"));
    System.out.println(result);
    //增删改必须要提交事务
    sqlSession.commit();
    sqlSession.close();
}

 

4.update

1.编写接口

//修改用户
int updateUser(User user);

2.编写对应的mapper中的sql语句

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

3.测试

@Test
public void Test4(){
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    int result = userMapper.updateUser(new User(4, "赵六", "12345678"));
    System.out.println(result);
    sqlSession.commit();
    sqlSession.close();
}

 

5.delete

1.编写接口

int deleteUser(int id);

2.编写对应的mapper中的sql语句

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

3.测试

@Test
public void Test5(){
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    int result = userMapper.deleteUser(4);
    System.out.println(result);
    sqlSession.commit();
    sqlSession.close();
}