OneToOne annotation 双向关联-优快云博客

本文链接：https://blog.youkuaiyun.com/hongmin118/article/details/84017631

本文解析了一对一关联关系在Hibernate中的实现方式，重点介绍了如何使用mappedBy属性来避免外键冗余，并通过Husband与Wife两个实体类的具体示例进行说明。

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package com.hibernate.entity;

import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;

@Entity
public class Husband implements Serializable {
	
	
	/**
	 * 
	 */
	private static final long serialVersionUID = 2476364405175138004L;

	
	private int id;
	
	private String name;
	
	private Wife wife;
	
	
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}

	public String getName() {
		return name;
	}

	@OneToOne
	public Wife getWife() {
		return wife;
	}

	public void setId(int id) {
		this.id = id;
	}

	public void setName(String name) {
		this.name = name;
	}

	public void setWife(Wife wife) {
		this.wife = wife;
	}
	
	
}

package com.hibernate.entity;

import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;

@Entity
public class Wife implements Serializable {
	
	/**
	 * 
	 */
	private static final long serialVersionUID = 5270130768836331730L;

	
	private int id;
	
	private String name;
	
	private Husband husband;

	
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	@OneToOne(mappedBy="wife")
	public Husband getHusband() {
		return husband;
	}

	public void setHusband(Husband husband) {
		this.husband = husband;
	}
	
}

注意：Wife类的getHusband()上用了mappedBy"wife"

这个意思是说，我这里的OneToOne就不用管了，只用Husband里的getWife()上的OneToOne关系

生成的表为Husband参考Wife，有了wifeid，才能有Husband

Husband为这个关系的拥有者

如果Wife类的getHusband()只有@OneToOne，没有mappedBy，那么生成的两张表都会有对方的外键，造成外键冗余。