spring data jpa中的DTO查询

昨天收到一封邮件，问了我一个问题，问题如下：

SELECT COUNT(user.id),user_name FROM USER where user_name like "%?%" GROUP BY user_name,id类似这种的sql用spring data jpa怎么写？

下面就这个问题一起来探讨下，怎么解决？

1、新建Entity

package com.chhliu.springboot.jpa.entity;

import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="t_user")
public class User implements Serializable{

/**
*
*/
private static final long serialVersionUID = 1L;

@Id()
@GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private String name;
private String address;
private int age;
……省略getter、setter方法……
}

2、编写DTO

package com.chhliu.springboot.jpa.dto;

import java.io.Serializable;

public class UserDto implements Serializable{
/**
*
*/
private static final long serialVersionUID = 1L;
private Long num;
private String name;
public UserDto() {
super();
}
public UserDto(Long num, String name) {
super();
this.num = num;
this.name = name;
}
……省略getter、setter方法……
/**
* attention:
* Details：TODO
* @author chhliu
*/
@Override
public String toString() {
return "UserDto [num=" + num + ", name=" + name + "]";
}
}

方案一：使用@Query

1、编写Repository接口

package com.chhliu.springboot.jpa.repository;

import java.util.List;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;

import com.chhliu.springboot.jpa.dto.UserDto;
import com.chhliu.springboot.jpa.entity.User;

public interface UserRepository extends JpaRepository<User, Integer> {
@Query("select new com.chhliu.springboot.jpa.dto.UserDto(count(u.id), u.name) from User u where u.name like %:name% group by u.name, u.id)")
public List<UserDto> findByAndGroupByHql(@Param("name") final String name);
}

2、测试类

List<UserDto> list1 = repository.findByAndGroupByHql("chh");
if(null != list1 && !list1.isEmpty()){
for(UserDto list:list1){
System.out.println(list);
}
}

3、测试结果

Hibernate: select count(user0_.id) as col_0_0_, user0_.name as col_1_0_ from t_user user0_ where user0_.name like '%chh%' group by user0_.name , user0_.id
UserDto [num=1, name=chhliu]
UserDto [num=1, name=chhliuxyh]

方案二：使用原生的EntityManager

1、编写Repository管理类

package com.chhliu.springboot.jpa.repository;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.stereotype.Service;

import com.chhliu.springboot.jpa.dto.NumAndAddressDto;
import com.chhliu.springboot.jpa.dto.UserDto;
import com.chhliu.springboot.jpa.entity.User;

@Service
public class UserRepositoryManager {
@Autowired
@PersistenceContext
private EntityManager entityManager;// 注入EntityManager实例

public List<UserDto> findByAndGroup(final String name){
List<UserDto> list = entityManager
.createQuery("select new com.chhliu.springboot.jpa.dto.UserDto(count(u.id), u.name) from User u where u.name like '%"+name+"%' group by u.name, u.id")
.getResultList();

return list;
}
}

测试结果同上

方案三：使用CriteriaQuery查询

public List<UserDto> findAndReturnDto(final String address) {
/*
*  查询出地址，数量并根据地址分组，同时分组的数量大于2的所有结果集
*  下面的Criteria对应的完整sql语句如下：
*  select count(u.id) as num, u.address as address from t_user u where u.address = address group by u.address having count(u.id)>2
*/
CriteriaBuilder builder = entityManager.getCriteriaBuilder(); // 获取builder
CriteriaQuery<UserDto> query = builder.createQuery(UserDto.class);// 创建查询
Root<User> root = query.from(User.class);// 构建Root
query.multiselect(builder.count(root.get("id")), root.get("address"))// 多条件查询
.where(builder.equal(root.get("address"), address))// where子句
.groupBy(root.get("address")).having(builder.gt(builder.count(root.get("id")),2));
return entityManager.createQuery(query).getResultList();
}

测试结果如下：

UserDto [num=3, name=北京]