在關聯查詢中,有時我們需要吧a表中的id存到b表中的某個字段(aId)中,這是在分頁的時候發現我們不能在頁面中顯示aId,我們只需要a表的name屬性怎麼辦呢?我們需要給返回的Page對象重新賦值
在b的實體類中需要映射a.name字段,@Transient註解:表示該屬性並非一個到數據庫表的字段的映射
如:
public class Follow extends IdEntity {
private Long memberId;//會員id
private Long followMemberId;//被關注人id
@Transient
private String memberNickName;//另一個表需要映射的name
}
分頁查詢在service中
public Page<Follow> findByPage(Pageable pageable, String memberNickName) {
Specification<Follow> specification = new Specification<Follow>() {
@Override
public Predicate toPredicate(Root<Follow> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
List<Predicate> predicates = new ArrayList<>();
if(!memberNickName.isEmpty()||memberNickName!=null){
Member member = memberService.findByMemberNickName(memberNickName, MemberStatus.正常.getValue()) ;
if(member!=null){
CriteriaBuilder.In<Long> in = criteriaBuilder.in(root.get("memberId"));
in.value(member.getId());//模糊查詢
predicates.add(in);
}
}
return criteriaBuilder.and(predicates.toArray(new Predicate[0]));
}
};
Page<Follow> followList = followRepository.findAll(specification, pageable);
for(int i=0;i<followList.getContent().size();i++){
transformMember(followList,i);//轉化
}
return followList;
}
將獲取到的Content進行轉化、重新賦值
private void transformMember(Page<Follow> followList,int i){
Long memberId = followList.getContent().get(i).getMemberId();//獲取到b表中id
Optional<Member> member = memberService.findById(memberId);//通過b表的id去a表中查詢
followList.getContent().get(i).setMemberNickName(member.get().getNickname());
}
在controller中調用並返回