Question

کاربرد انوتیشن PrimaryKeyJoinColumn در JPA چیست؟

Answer 1

توسط  PrimaryKeyJoinColumn@  میتوان از primary key id یک جدول استفاده کرد به عنوان یک foreign key برای join زدن به یک جدول دیگر و برای رابطه OneToOne@ استفاده کرد. به عنوان مثال : 

<<     Biography class //

import javax.persistence.*;  
  
@Entity  
@Table(name="biographies")  
public class Biography {  
      
    @Id  
    @Column(name="author_id")  
    private Integer authorId;  
      
    private String information;  
  
    public Integer getAuthorId() {  
        return authorId;  
    }  
  
    public void setAuthorId(Integer authorId) {  
        this.authorId = authorId;  
    }  
  
    public String getInformation() {  
        return information;  
    }  
  
    public void setInformation(String information) {  
        this.information = information;  
    }  
      
}  

>>

 <<    Author class //

import javax.persistence.*; 
 
@Entity 
@Table(name="authors") 
public class Author { 
 
    @Id 
    @GeneratedValue 
    private Integer id; 
     
    private String name; 
     
    @OneToOne(cascade=CascadeType.ALL) 
    @PrimaryKeyJoinColumn 
    private Biography biography; 
 
    public Integer getId() { 
        return id; 
    } 
 
    public void setId(Integer id) { 
        this.id = id; 
    } 
 
    public String getName() { 
        return name; 
    } 
 
    public void setName(String name) { 
        this.name = name; 
    } 
 
    public Biography getBiography() { 
        return biography; 
    } 
 
    public void setBiography(Biography biography) { 
        this.biography = biography; 
    } 
     
}

حالا نحوه استفاده در کد :

public static void main(String[] args) {  
  
        SessionFactory sessionFactory = HibernateUtil.getSessionFactory();  
        Session session = sessionFactory.openSession();  
        session.beginTransaction();  
          
        Author author = new Author();  
        author.setName("full name");  
          
        session.persist(author);  
          
        Biography biography = new Biography();  
        biography.setInformation("some information. ......");  
        biography.setAuthorId(author.getId());  
          
        author.setBiography(biography);  
          
        session.save(author);  
          
        session.getTransaction().commit();  
          
        session.close();  
  
    }