前言：有兩個表order和item，資料庫模型如下：

sql：

/*
Navicat MySQL Data Transfer

Source Server         : lalala
Source Server Version : 50720
Source Host           : localhost:3306
Source Database       : test

Target Server Type    : MYSQL
Target Server Version : 50720
File Encoding         : 65001

Date: 2018-07-05 17:10:13
*/

SET FOREIGN_KEY_CHECKS=0;

-- ----------------------------
-- Table structure for item
-- ----------------------------
DROP TABLE IF EXISTS `item`;
CREATE TABLE `item` (
  `id` int(11) NOT NULL,
  `content` varchar(255) DEFAULT NULL,
  `order_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `fk_item_order_01` (`order_id`),
  CONSTRAINT `fk_item_order_01` FOREIGN KEY (`order_id`) REFERENCES `order` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

-- ----------------------------
-- Table structure for order
-- ----------------------------
DROP TABLE IF EXISTS `order`;
CREATE TABLE `order` (
  `id` int(11) NOT NULL,
  `content` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
 

order與item是一對多的關係

package com.test.domain;

import java.util.HashSet;
import java.util.Set;

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

import com.fasterxml.jackson.annotation.JsonInclude;

@Entity
@Table(name = "order")
@JsonInclude(JsonInclude.Include.NON_NULL)
public class Order {
	private Integer id;
	private String content;
	private Set<Item> item = new HashSet<>();
	
	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	@Column(unique = true, nullable = false)
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getContent() {
		return content;
	}
	public void setContent(String content) {
		this.content = content;
	}
	
	@OneToMany(cascade = CascadeType.ALL, mappedBy = "order")
	public Set<Item> getItem() {
		return item;
	}
	public void setItem(Set<Item> item) {
		this.item = item;
	}
	
	public void create(Order order){
		this.content = order.content;
		this.item = order.item;
	}
}
 

package com.test.domain;

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;

import com.fasterxml.jackson.annotation.JsonInclude;

@Entity
@Table(name = "item")
@JsonInclude(JsonInclude.Include.NON_NULL)
public class Item {
	
	private Integer id;
	private String content;
	private Order order;
	
	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	@Column(unique = true, nullable = false)
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getContent() {
		return content;
	}
	public void setContent(String content) {
		this.content = content;
	}
	
	@ManyToOne
	@JoinColumn(name = "order_id")
	public Order getOrder() {
		return order;
	}
	public void setOrder(Order order) {
		this.order = order;
	}
	
    public void create(Order order) {
		this.order = order;
	}
}
 

達到效果：在儲存order的時候一併將item儲存，而且item裡面的外來鍵要有值。

@PostMapping
	public Result<Void> addOrder(@RequestBody College input) {
		Order order=  new Order();
	        //將主表的主鍵存放到子表的外來鍵中  關鍵點
		for(Item item : input.getItem()) {
			item.create(order);
		}
		order.create(input);
		orderRepository.save(order);
		return Result.success();
	}