springboot之jpa高级查询操作代码示例

本篇文章小编给大家分享一下springboot之jpa高级查询操作代码示例，文章代码介绍的很详细，小编觉得挺不错的，现在分享给大家供大家参考，有需要的小伙伴们可以来看看。

springboot的jpa可以根据方法名自动解析sql 非常方便, 只需要在 dao接口中定义方法即可;

下面是一个 demo

package com.bus365.root.dao; 
import java.io.Serializable;
import java.util.List; 
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param; 
import com.bus365.root.model.User; 
public interface UserDao extends JpaRepository,JpaSpecificationExecutor,Serializable { 
 User findByName(String name); 
 User findByNameAndAge(String name, Integer age); 
 User findByNameOrAge(String name, Integer age); 
 
 /*@Query(value = "from User where name = :name")
 List findbyname(@Param("name") String name);*/
}

下面展示service层调用:

@Override
 public User findByName(String name) {
 User user = userDao.findByName(name);
 return user;
 }
 
 @Override
 public User findByNameAndAge(String name, Integer age) {
 User user = userDao.findByNameAndAge(name,age);
 return user;
 }
 
 @Override
 public User findByNameOrAge(String name, Integer age) {
 User user = userDao.findByNameOrAge(name,age);
 return user;
 }

具体的关键字，使用方法和生产成SQL如下表所示

下面介绍使用java原生的jpa操作数据库,对jpa熟悉的朋友应该很快就能理解,springboot使用原生jpa的关键是引入entitymanger

看一下service层

package com.bus365.root.service.impl; 
import java.util.List; 
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext; 
import org.springframework.stereotype.Service; 
import com.bus365.root.model.Address;
import com.bus365.root.service.AddressService;
 
@Service
public class AddressServiceImpl implements AddressService {
 
	@PersistenceContext
	private EntityManager entityManager;
	
	public List
 listAddress(){
		List resultList = entityManager.createNativeQuery("select * from address ", Address.class).getResultList();
		return resultList;
	}
}

注意 @PersistenceContext

private EntityManager entityManager;

动态引入entitymanger , 之后就能正常使用了;

createNativeQuery是操作原生mysql方法;支持跨表查询;

jpa的事务 直接使用注解Transactional 参数rollbackon表示回滚条件, 这个注解一搬加在service层; 注意getSingleResult 如果查不到数据会报错;

@Transactional(rollbackOn= {Exception.class})
 public Address getAddressByid(Long id) {
 Address singleResult = null;
 try {
  singleResult = (Address) entityManager
   .createNativeQuery("select * from address where id = :id", Address.class).setParameter("id", id)
   .getSingleResult();
 } catch (Exception e) {
  e.printStackTrace();
 }
 return singleResult;
 }

jpa实现多表联查;

@Transactional
 public List getUserWithAddrByid(Long id) {
 List resultList = entityManager.createNativeQuery(
  "select u.id id,u.age age,u.name name,a.name aname,a.completeaddress addre from user u left join address a on u.addressid = a.id where u.id = :id")
  .setParameter("id", id).getResultList();
 return resultList;
 }

这是一个联查user 和address的例子, 返回的结果是个List 项目中一般封装成vo 类,或者List> 的形式

github项目地址https://github.com/Christain1993/SpringBootIntegration