在关联查询中,有时我们需要吧a表中的id存到b表中的某个字段(aId)中,这是在分页的时候发现我们不能在页面中显示aId,我们只需要a表的name属性怎么办呢?我们需要给返回的Page对象重新赋值
在b的实体类中需要映射a.name字段,@Transient注解:表示该属性并非一个到数据库表的字段的映射
如:
public class Follow extends IdEntity {
private Long memberId;//会员id
private Long followMemberId;//被关注人id
@Transient
private String memberNickName;//另一个表需要映射的name
}
分页查询在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());//模糊查询
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);//转化
}
return followList;
}
将获取到的Content进行转化、重新赋值
private void transformMember(Page<Follow> followList,int i){
Long memberId = followList.getContent().get(i).getMemberId();//获取到b表中id
Optional<Member> member = memberService.findById(memberId);//通过b表的id去a表中查询
followList.getContent().get(i).setMemberNickName(member.get().getNickname());
}
在controller中调用并返回