java bean join_spring data jpa 关联join查询出自定义实体java bean的坑

repository接口如下：

package cn.detao.repository;

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

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

import cn.detao.domain.Role;

import cn.detao.domain.User;

import java.lang.String;

import java.util.List;

public interface UserRepository extends JpaRepository{

User findByName(String name);

User findByUsername(String username);

@Query(value = "SELECT new cn.detao.domain.Role(r.id,r.name,r.nameZh) FROM User u INNER JOIN UserRole ur ON u.id = ur.userId INNER JOIN Role r ON ur.roleId = r.id WHERE u.id = ?1")

ListfindRolesByUser(Integer UserId);

}

role实体：

package cn.detao.domain;

import javax.persistence.Column;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.GenerationType;

import javax.persistence.Id;

import lombok.Data;

@Entity

@Data

public class Role {

@Id // 主键

@GeneratedValue(strategy = GenerationType.IDENTITY) // 自增长策略

private Integer id;

@Column

private String name;

@Column

private String nameZh;

public Role(Integer id, String name, String nameZh) {

super();

this.id = id;

this.name = name;

this.nameZh = nameZh;

}

public Role() {

}

}

注意大坑：

SELECT new cn.detao.domain.Role(r.id,r.name,r.nameZh) FROM User u INNER JOIN UserRole ur ON u.id = ur.userId INNER JOIN Role r ON ur.roleId = r.id WHERE u.id = ?1

查询语句中的所有表名必须是 javaBean 实体名，不能是mysql表名；字段名也必须是javaBean实体里的属性名，不能是mysql表里的字段名。