jpa单向多对一关联映射

表结构

student

class

Class

package auth.model;

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

@Entity
@Table(name="class")
public class Room {
	private int id;
	private String name;
	@Id
	@GeneratedValue(strategy= GenerationType.AUTO)
	@Column(name="id")
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	@Column(name="name")
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}

Student

package auth.model;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

@Entity
@Table(name="student")
public class Student {
	private int id;
	public int room_id;
	private String name;
	private Room room;
	@GeneratedValue(strategy= GenerationType.AUTO)
	@Id
	@Column(name="id")
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	@Column(name="name")
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	@Column(name="room_id")
	public int getRoom_id() {
		return room_id;
	}
	public void setRoom_id(int room_id) {
		this.room_id = room_id;
	}
	@ManyToOne
    @JoinColumn(name = "room_id",insertable=false, updatable=false)
	public Room getRoom() {
		return room;
	}
	public void setRoom(Room room) {
		this.room = room;
	}

}

测试

package auth.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.alibaba.fastjson.JSONObject;

import auth.dao.ClassDao;
import auth.dao.StudentDao;
import auth.model.Room;
import auth.model.Student;

@Service
public class StudentController {
	@Autowired
	private ClassDao dao;
	@Autowired
	private StudentDao stuDao;
	public void add(){
		Room room=new Room();
		room.setName("10班");
		Student s=new Student();
		dao.save(room);
		s.setName("小李5");
		s.setRoom(room);
		stuDao.save(s);
	}
	public void query(){
		Student s=stuDao.findOne(2);
		System.out.println(JSONObject.toJSONString(s));

	}
	public void query1(){
		Room s=dao.findOne(2);
		System.out.println(JSONObject.toJSONString(s));

	}

}

过程:

insert
    into
        class
        (name)
    values
        (?)

        auth.model.Room{name=11班, id=20}

        insert
    into
        student
        (name, room_id)
    values
        (?, ?)
2017-06-11 23:39:52,763 DEBUG [org.hibernate.id.IdentifierGeneratorHelper:94] - Natively generated identity: 24
2017-06-11 23:39:52,766 DEBUG [org.hibernate.engine.transaction.spi.AbstractTransactionImpl:175] - committing
2017-06-11 23:39:52,767 DEBUG [org.hibernate.event.internal.AbstractFlushingEventListener:149] - Processing flush-time cascades
2017-06-11 23:39:52,767 DEBUG [org.hibernate.event.internal.AbstractFlushingEventListener:189] - Dirty checking collections
2017-06-11 23:39:52,768 DEBUG [org.hibernate.event.internal.AbstractFlushingEventListener:123] - Flushed: 0 insertions, 0 updates, 0 deletions to 1 objects
2017-06-11 23:39:52,768 DEBUG [org.hibernate.event.internal.AbstractFlushingEventListener:130] - Flushed: 0 (re)creations, 0 updates, 0 removals to 0 collections
2017-06-11 23:39:52,772 DEBUG [org.hibernate.internal.util.EntityPrinter:114] - Listing entities:
2017-06-11 23:39:52,772 DEBUG [org.hibernate.internal.util.EntityPrinter:121] - auth.model.Student{room_id=0, name=小李6, id=24, room=auth.model.Room#20}
{"id":2,"name":"李明","room":{"id":1,"name":"12班"},"room_id":1}
{"id":2,"name":"24班"}

数据库结果：