hibernate 一對一外鍵關聯

一對一單向外鍵關聯：一夫一妻，是一對一的關係。建Husband 和Wife類。

public class Husband {
    private int id;
    private String name;

    // 丈夫和妻子，一夫一妻，一對一關聯。丈夫裏面有Wife的引用，Wife裏面沒有設定Husband引用，單向引用。
    private Wife wife;
         @Id
     @GeneratedValue
    public int getId() {
        return id;
    }
     @OneToOne//一對一
     //@JoinColumn與@Column標記一樣，是用於註釋表中的字段的。
     @JoinColumn(name="wife_Id")

    public Wife getWife() {
        return wife;
    }
    get、set方法省略.........
}
public class Wife {
      private int id;
      private String name;
     @Id
     @GeneratedValue
    public int getId() {
        return id;
    }
      get、set方法省略.........
}

@Test
    public void save(){ 
        Husband h=new Husband();
        h.setName("lilei"); 
        Wife wife=new Wife();       
        wife.setName("hanmeimei");  
        h.setWife(wife);


        Configuration con= new AnnotationConfiguration();
        SessionFactory sf=con.configure().buildSessionFactory();
        Session session=sf.getCurrentSession();
        session.beginTransaction();
        session.save(wife);
        session.save(h);
        session.getTransaction().commit(); 
        sf.close();

    }
    控制檯打印結果：
    Hibernate: 
    insert 
    into
        Wife
        (name) 
    values
        (?)
Hibernate: 
    insert 
    into
        Husband
        (name, wife_Id) //wife_Id) 外鍵
    values
        (?, ?)

一對一雙向外鍵關聯：只改動Wife即可。

@Entity
public class Wife {
    private int id;
    private String name;
    private Husband husband;
    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }
     //設置mappedby.否則兩邊都設外鍵會顯得特別冗餘，好像還會經常報錯。
    @OneToOne(mappedBy="wife") 
    public Husband getHusband() {
        return husband;
    }
    //其他省略...
}

Hibernate: 
    insert 
    into
        Wife
        (name) 
    values
        (?)
Hibernate: 
    insert 
    into
        Husband
        (name, wife_Id) 
    values
        (?, ?)

一對一單向外鍵關聯和一對一雙向外鍵關聯，在數據庫中沒有區別，在後臺代碼中單向我們的wife找不到husband，而雙向中可以找到。好像也沒什麼區別………….