参考:https://blog.csdn.net/qq_36144258/article/details/80298354
近期一个项目用到Spring Data Jpa,Jpa用来做单表查询非常的简单粗暴,可以说不用写sql,但是涉及到复杂的多表操作,还是要写sql,这个时候需要用到@Query注解。@Query用法可见https://mp.csdn.net/postedit/82797015
@Query(value = "select new com.squid.service.dto.MyFriendDTO(uil.createdTime as inviteTime,ui.nickname as name,ui.grade as grade) from UserInviteLog as uil left join UserInfo as ui on uil.userId = ui.id where uil.inviteUserId = :userId and ui.grade > :grade",
countQuery = "select count(uil.id) from UserInviteLog as uil left join UserInfo as ui on uil.userId = ui.id where uil.inviteUserId = :userId and ui.grade > :grade")
Page<MyFriendDTO> findElitedByInviteUserId(@Param("userId")Long userId, @Param("grade")Integer grade, Pageable pageable);
com.squid.service.dto.MyFriendDTO是需要返回的实体类相当于我们XML中的resultMap,这个地方需要注意的是,一定要重写返回的实体类的构造方法(具体参数根据new创建的参数设置,这里是三参inviteTime、name、grade),否则将new失败。
public MyFriendDTO(Long inviteTime, String name, Integer grade) {
this.inviteTime = inviteTime;
this.name = name;
this.grade = grade;
}
也可以不返回具体实体类直接返回List<Map<String, Object>>不过分页就不好处理了。
countQuery就是为了配合Page计算总条数的。
分页入参Pageable,我们和单表分页一样直接丢进去,springdata会帮我们处理好。