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); 

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。