【Mybatis】实现修改、删除和查询功能

1.修改和删除

（1）UserMapper接口中添加方法

public interface UserMapper {
    int insertUser(User user);

    int updateUser(int id,User user);
    
    int deleteUser(int id);
}

（2）映射文件SQL语句

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

    <update id="updateUser" parameterType="Integer">
        update user set name="熊初墨" where id=#{id};
    </update>

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

（3）测试

    @Test
    public void test3() throws IOException {
        InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
        SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(is);
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        int updateLine = mapper.updateUser(99);
        int deleteLine = mapper.deleteUser(99);
    }

2.查询

2.1 根据id查询用户信息

（1）Mapper接口方法

    User getUserById(Integer id);

（2）映射文件
parameterType：参数类型
resultType：查询结果集类型

• resultTye：自动映射，用于属性名和表中字段名一致的情况
• resultMap：自定义映射，用于一对多、多对一或字段名和属性名不一致的情况

    <select id="getUserById" parameterType="Integer" resultType="com.pxk.pojo.User">
        select * from user where id = #{id}
    </select>

（3）测试

        User user = mapper.getUserById(100);
        System.out.println(user);

2.2 查询所有用户信息

（1）Mapper接口方法

    List<User> getAllUser();

（2）映射文件

    <select id="getAllUser" resultType="com.pxk.pojo.User">
        select * from user;
    </select>

（3）测试

        List<User> users = mapper.getAllUser();
        users.forEach(user -> System.out.println(user));