spring data jpa 分页查询(小结)

原文:https://www.cnblogs.com/hdwang/p/7843405.html

spring data jpa 分页查询

方法一（本地sql查询,注意表名啥的都用数据库中的名称，适用于特定数据库的查询）

public interface UserRepository extends JpaRepository<User, Long> {

  @Query(value = "SELECT * FROM USERS WHERE LASTNAME = ?1",
    countQuery = "SELECT count(*) FROM USERS WHERE LASTNAME = ?1",
    nativeQuery = true)
  Page<User> findByLastname(String lastname, Pageable pageable);
}

方法二（jpa已经实现的分页接口，适用于简单的分页查询）

public interface PagingAndSortingRepository<T, ID extends Serializable>
  extends CrudRepository<T, ID> {

  Iterable<T> findAll(Sort sort);

  Page<T> findAll(Pageable pageable);
}

Accessing the second page of User by a page size of 20 you could simply do something like this:

PagingAndSortingRepository<User, Long> repository = // … get access to a bean
Page<User> users = repository.findAll(new PageRequest(1, 20));

User findFirstByOrderByLastnameAsc();

User findTopByOrderByAgeDesc();

Page<User> queryFirst10ByLastname(String lastname, Pageable pageable);

Slice<User> findTop3ByLastname(String lastname, Pageable pageable);

List<User> findFirst10ByLastname(String lastname, Sort sort);

List<User> findTop10ByLastname(String lastname, Pageable pageable);

//service
 Sort sort = new Sort(Sort.Direction.DESC,"createTime"); //创建时间降序排序
 Pageable pageable = new PageRequest(pageNumber,pageSize,sort);
 this.depositRecordRepository.findAllByUserIdIn(userIds,pageable);

//repository
Page<DepositRecord> findAllByUserIdIn(List<Long> userIds,Pageable pageable);

方法三（Query注解,hql语局，适用于查询指定条件的数据）

 @Query(value = "select b.roomUid from RoomBoard b where b.userId=:userId and b.lastBoard=true order by  b.createTime desc")
    Page<String> findRoomUidsByUserIdPageable(@Param("userId") long userId, Pageable pageable);

Pageable pageable = new PageRequest(pageNumber,pageSize);
Page<String> page = this.roomBoardRepository.findRoomUidsByUserIdPageable(userId,pageable);
List<String> roomUids = page.getContent();

可以自定义整个实体(Page<User>)，也可以查询某几个字段（Page<Object[]>），和原生sql几乎一样灵活。

方法四（扩充findAll，适用于动态sql查询）

public interface UserRepository extends JpaRepository<User, Long> {

    Page<User> findAll(Specification<User> spec, Pageable pageable);
} 

@Service
public class UserService {

    @Autowired
    private UserRepository userRepository;

    public Page<User> getUsersPage(PageParam pageParam, String nickName) {
        //规格定义
        Specification<User> specification = new Specification<User>() {

            /**
             * 构造断言
             * @param root 实体对象引用
             * @param query 规则查询对象
             * @param cb 规则构建对象
             * @return 断言
             */
            @Override
            public Predicate toPredicate(Root<User> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
                List<Predicate> predicates = new ArrayList<>(); //所有的断言
                if(StringUtils.isNotBlank(nickName)){ //添加断言
                    Predicate likeNickName = cb.like(root.get("nickName").as(String.class),nickName+"%");
                    predicates.add(likeNickName);
                }
                return cb.and(predicates.toArray(new Predicate[0]));
            }
        };
        //分页信息
        Pageable pageable = new PageRequest(pageParam.getPage()-1,pageParam.getLimit()); //页码：前端从1开始，jpa从0开始，做个转换
        //查询
        return this.userRepository.findAll(specification,pageable);
    }

}