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);

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。