欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页  >  IT编程

spring data jpa分页查询示例代码

程序员文章站 2024-03-04 23:03:00
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...

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。