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, JpaSpecificationExecutor { 
   
  @Query("select c from CameraInfoPO c where c.deviceInfo.id = ?1") 
  public List 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 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 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 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 rootFrom = criteriaQuery.from(CameraInfoPO.class); 
     
    //查询条件 
    List predicates = new ArrayList(); 
     
    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 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 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 pageRst = 
      new PageImpl(createQuery.getResultList(), pageable, createCountQuery.getResultList().size()); 
    return pageRst; 
     
  } 
   
  //制造查询条件结果(建议存放map) 
  private Specification getWhereClause(final Integer isEnabled) { 
    return new Specification() { 
      public Predicate toPredicate(Root 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 findCameraInfoByPageForJpa(Pageable pageable, Integer isEnabled) { 
     
    Specification spec = getWhereClause(isEnabled); 
     
    Page 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 page = cameraInfoRepo.findByIsEnabled(1, pageable); 

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