在@Mapper注解下来编写SQL语句

SpringBoot项目在mapper接口层使用了@Mapper注解后，就不需要在启动类中使用@MapperScan来扫描mapper接口层文件。

@Mapper
@Repository
public interface UserMapper {


	/**模糊查询**/
    @Select("SELECT a.id, a.username, a.password FROM User a WHERE a.username LIKE CONCAT('%',#{0},'%') ")
    public List<User> selectByName(String username);

	/**将查询到的字段进行映射到对应的java对象内**/
    @Select("select f.user_id user_id, f.type_id, f.friend_id, u.displayname username, u.gajgjgmc sign, u.tel phone, u.avatar from im_friend f left join sys_user u on f.friend_id=u.username where f.user_id= #{userId}")
    @Results(value = {
            @Result(column = "user_id", property = "userId"),
            @Result(column = "type_id", property = "typeId"),
            @Result(column = "friend_id", property = "friendId"),
            @Result(column = "username", property = "username"),
            @Result(column = "sign", property = "sign"),
            @Result(column = "phone", property = "phone"),
            @Result(column = "avatar", property = "avatar"),
    })
    List<UserFriend> findUserFriend(String userId);
    
	/**
     * 根据用户ID修改头像
     * @param userId 用户ID
     * @param imgUrl 修改的url
     */
    @Update("update sys_user set avatar = #{imgUrl} where username = #{userId}")
    void changeHeadPicture(@Param("userId")String userId,@Param("imgUrl")String imgUrl);
}