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

100

									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; 

									  } 

									}