JPA---一对一关系

在JPA中，使用@oneToOne来标示。

package com.yl.demo1.bean.oneToone;



import javax.persistence.CascadeType;

import javax.persistence.Column;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.JoinColumn;

import javax.persistence.OneToOne;



@Entity

public class User {

    private Integer id;

    private String name;

    private IDCard idcard;

    

    public User(){}

    

    public User(String name) {

        super();

        this.name = name;

    }

    @Id @GeneratedValue

    public Integer getId() {

        return id;

    }

    public void setId(Integer id) {

        this.id = id;

    }

    @Column(length=10, nullable=false)

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    @OneToOne(optional=false, cascade=CascadeType.ALL)

    @JoinColumn(name="idcard_id")

    public IDCard getIdcard() {

        return idcard;

    }

    public void setIdcard(IDCard idcard) {

        this.idcard = idcard;

    }

    

    

}

 

 1 package com.yl.demo1.bean.oneToone;

 2 

 3 import javax.persistence.CascadeType;

 4 import javax.persistence.Column;

 5 import javax.persistence.Entity;

 6 import javax.persistence.GeneratedValue;

 7 import javax.persistence.Id;

 8 import javax.persistence.OneToOne;

 9 

10 @Entity

11 public class IDCard {

12     private Integer id;

13     private String cardno;

14     private User user;

15     

16     public IDCard(){}

17     

18     public IDCard(String cardno) {

19         super();

20         this.cardno = cardno;

21     }

22     @Id @GeneratedValue

23     public Integer getId() {

24         return id;

25     }

26     public void setId(Integer id) {

27         this.id = id;

28     }

29     @Column(length=18, nullable=false)

30     public String getCardno() {

31         return cardno;

32     }

33     public void setCardno(String cardno) {

34         this.cardno = cardno;

35     }

36     /**

37      * 在一对一的关系中，出现mappedBy的对象为关系的被维护端

38      * 

39      */

40     @OneToOne(mappedBy="idcard", cascade={CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH})

41     public User getUser() {

42         return user;

43     }

44     public void setUser(User user) {

45         this.user = user;

46     }

47     

48     

49 }

 常见操作：

 1 @Test

 2     public void save() {

 3         EntityManagerFactory factory = Persistence.createEntityManagerFactory("YL");

 4         EntityManager em = factory.createEntityManager();

 5         em.getTransaction().begin();//事务开始

 6         

 7         User user = new User("ylll");

 8         user.setIdcard(new IDCard("123456789012345678"));

 9         

10         em.persist(user);

11         

12         em.getTransaction().commit();

13         em.close();

14         factory.close();

15     }