spring data jpa分页查询示例代码

最近项目上用就hibernate+spring data jpa，一开始感觉还不错，但是随着对业务的复杂，要求处理一些复杂的sql，就顺便研究了下，把结果记录下，以便日后查看。用到Specification，需要继承JpaSpecificationExecutor接口。（下面代码有的分页从0开始作为第一页，有的从1开始作为作为第一页，我也忘记，请自己测试）

DAO层：

import java.util.List;  
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.data.jpa.repository.Modifying;
import org.springframework.data.jpa.repository.Query;
import org.springframework.stereotype.Repository;

@Repository
public interface CameraInfoRepo extends JpaRepository<CameraInfoPO, String>, JpaSpecificationExecutor<CameraInfoPO> {

@Query("select c from CameraInfoPO c where c.deviceInfo.id = ?1")
 public List<CameraInfoPO> findCamerasByDeviceId(String listDeviceInfoId);

//更新之后不清空缓存，在一个事务里查询到旧数据(hibernate)
 @Modifying
 @Query(value = "update CameraInfoPO c set c.isEnabled = 1 where c.id = ?1")
 public void updateEnabled(String cameraId);

//更新之后清空缓存，不保留旧对象(hibernate)
 @Modifying(clearAutomatically = true)
 @Query(value = "update CameraInfoPO c set c.isEnabled = 0 where c.id = ?1")
 public void updateUnEnabled(String cameraId);

//带条件的分页查询    
 public Page<CameraInfoPO> findByIsEnabled(Integer isEnabled, Pageable pageable);

}

DAO实现层

import java.util.ArrayList;
import java.util.List;

import javax.annotation.Resource;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.TypedQuery;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;

import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageImpl;
import org.springframework.data.domain.Pageable;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.stereotype.Repository;

@Repository
public class CameraInfoRepoImpl {

@PersistenceContext
 private EntityManager em;

@Resource
 private CameraInfoRepo cameraInfoRepo;

public Page<CameraInfoPO> findCameraInfoByPage(Pageable pageable, Integer isEnabled) {

//CriteriaBuilder,用来构建CritiaQuery的构建器对象
   CriteriaBuilder criteriaBuilder = em.getCriteriaBuilder();

//CriteriaQuery,它包含着查询语句的条件各个部分，比如：select 、from、where、group by、order by等
   CriteriaQuery<CameraInfoPO> criteriaQuery = criteriaBuilder.createQuery(CameraInfoPO.class);

//查询根，用于获取查询实例的属性，通过CriteriaQuery的from方法获取
   Root<CameraInfoPO> rootFrom = criteriaQuery.from(CameraInfoPO.class);

//查询条件
   List<Predicate> predicates = new ArrayList<Predicate>();

if (null != isEnabled) {
     Predicate predicate = criteriaBuilder.equal(rootFrom.get("isEnabled").as(Integer.class), isEnabled);
     predicates.add(predicate);

}

//格式化参数
   criteriaQuery.where(criteriaBuilder.and(predicates.toArray(new Predicate[predicates.size()])));

//默认按照id排序（从小到大）
   criteriaQuery.orderBy(criteriaBuilder.asc(rootFrom.get("id")));

//SQL查询对象
   TypedQuery<CameraInfoPO> createQuery = em.createQuery(criteriaQuery);

//分页参数
   Integer pageSize = pageable.getPageSize();
   Integer pageNo = pageable.getPageNumber();

//计数查询结果条数
   TypedQuery<CameraInfoPO> createCountQuery = em.createQuery(criteriaQuery);

// 实际查询返回分页对象
   int startIndex = pageSize * pageNo;
   createQuery.setFirstResult(startIndex);
   createQuery.setMaxResults(pageable.getPageSize());
   Page<CameraInfoPO> pageRst =
     new PageImpl<CameraInfoPO>(createQuery.getResultList(), pageable, createCountQuery.getResultList().size());
   return pageRst;

}

//制造查询条件结果(建议存放map)
 private Specification<CameraInfoPO> getWhereClause(final Integer isEnabled) {
   return new Specification<CameraInfoPO>() {
     public Predicate toPredicate(Root<CameraInfoPO> r, CriteriaQuery<?> q, CriteriaBuilder cb) {
       Predicate predicate = cb.conjunction();
       if (null != isEnabled) {

predicate = cb.equal(r.get("isEnabled").as(Integer.class), isEnabled);
       }

return predicate;
     }
   };
 }

//单表根据查询条件的分页
 public Page<CameraInfoPO> findCameraInfoByPageForJpa(Pageable pageable, Integer isEnabled) {

Specification<CameraInfoPO> spec = getWhereClause(isEnabled);

Page<CameraInfoPO> pageRst = cameraInfoRepo.findAll(spec, pageable);

return pageRst;

}

}

还有另外一种就更简单了，如果只是根据表里面的一个或者几个字段，可以直接写jpa实现，不用复杂

Pageable pageable = new PageRequest(1, 1);
Page<CameraInfoPO> page = cameraInfoRepo.findByIsEnabled(1, pageable);

来源：http://blog.csdn.net/rshw123456/article/details/51694129