【hibernate框架】一对一双向外键关联(Annotation实现)

一对一双向外键关联(Annotation方法):


一夫(Husband)一妻(Wife)的一对一双向外键关联
Husband和Wife实体类：

package cn.edu.hpu.one2one;


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


@Entity
public class Husband {
	private int id;
	private String name;
	private Wife wife;


	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	
	@OneToOne
	@JoinColumn(name="wifeid")
	public Wife getWife() {
		return wife;
	}
	public void setWife(Wife wife) {
		this.wife = wife;
	}
	
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}	
	
}

package cn.edu.hpu.one2one;


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


@Entity
public class Wife {
	private int id;
	private String name;
	private Husband husband;


	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	
	@OneToOne
	public Husband getHusband() {
		return husband;
	}
	public void setHusband(Husband husband) {
		this.husband = husband;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}	
}

生成的建表语句：
alter table Husband 
        drop 
        foreign key FKAEEA401BC6294CED


    alter table Wife 
        drop 
        foreign key FK29233185D75BEA


    drop table if exists Husband


    drop table if exists Wife


    create table Husband (
        id integer not null auto_increment,
        name varchar(255),
        wifeid integer,
        primary key (id)
    )


    create table Wife (
        id integer not null auto_increment,
        name varchar(255),
        husband_id integer,
        primary key (id)
    )


    alter table Husband 
        add index FKAEEA401BC6294CED (wifeid), 
        add constraint FKAEEA401BC6294CED 
        foreign key (wifeid) 
        references Wife (id)


    alter table Wife 
        add index FK29233185D75BEA (husband_id), 
        add constraint FK29233185D75BEA 
        foreign key (husband_id) 
        references Husband (id)




双向关联在数据库中只需一边设置外键就行了,所以wife的husband_id就可以不要

mappedBy="wife"告诉hibernate，Wife和husband之间是一个1对1的关联，
对方husband类的wife属性已经做映射了,你就不用管我生成的外键的关联了
对方那边是主导，你不用管我这边的设置
这个时候wife建表语句中就没有husband_id属性了


凡是双向关联必设mappedBy


所以wife实体类注解写成：
@OneToOne(mappedBy="wife")
public Husband getHusband() {
return husband;
}

生成的表中wife就没有husband_id字段了

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