JPA级联在双向关联中不使用Hibernate？

Question

我已阅读cascadesJPA和hibernate几个帖子。我试了一下，但都没有帮助。

我想保存一个电影对象（其中有oneToMany与演员关联）。电影对象是持久的，但与电影关联的演员对象不是。

这里是我entity类：

@Entity 
public class Movie { 

    @Id 
    @Column(name="MOVIE_ID") 
    @GeneratedValue 
    private Long id; 

    @Column(name="MovieName") 
    private String name; 

    @Column(name="Date_Released") 
    private Date date; 

    @OneToMany(mappedBy="movie",fetch=FetchType.EAGER,cascade=CascadeType.PERSIST) 
    private Set<Actor> actors=new HashSet<>(); 

    public Movie(){} 

    public Movie(String name, Date released){ 
     this.name=name; 
     this.date=released; 
    } 


    public Long getId() { 
     return id; 
    } 

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

    public String getName() { 
     return name; 
    } 

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

    public Date getDate() { 
     return date; 
    } 

    public void setDate(Date date) { 
     this.date = date; 
    } 

    public Set<Actor> getActors() { 
     return actors; 
    } 

    public void setActors(Set<Actor> actors) { 
     this.actors = actors; 
    } 

    public String toString(){ 
     return id + " : " + name + " : " + date; 
    } 

    public void addActor(Actor a){ 
     getActors().add(a); 
    } 

} 

@Entity 
public class Actor { 
    @Id 
    @Column(name="ACTOR_ID") 
    @GeneratedValue 
    private Long id; 

@Column(name="ACTOR_NAME") 
private String name; 

@ManyToOne(fetch=FetchType.EAGER) 
@JoinColumn(name="ACTOR_MOVIE") 
private Movie movie; 


public Actor(){} 

public Actor(String name){ 
    this.name=name; 
} 


public Long getId() { 
    return id; 
} 

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


public String getName() { 
    return name; 
} 

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


public Movie getMovie() { 
    return movie; 
} 

public void setMovie(Movie movie) { 
    this.movie = movie; 
} 

public String toString(){ 
    return name + " : " + movie.getName(); 
} 

}

方案1个关联电影演员

public class HibernateTest { 

    public static void main(String[] args) { 

      Movie movie1 = new Movie("Mr and Mrs.Smith", new Date(2005, 6, 5)); 
      Actor actor3=new Actor("Brad"); 
      Actor actor4=new Actor("Joe"); 
      movie1.getActors().add(actor3); 
      movie1.getActors().add(actor4); 

     SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory(); 
     Session session = sessionFactory.openSession(); 
     session.beginTransaction(); 
     session.persist(movie1); 
     session.getTransaction().commit(); 
     session.close(); 

    } 
} 

，当我看着桌子上，我看到一排中创建电影表和演员表中的两行。但是没有关联。 actor表上的actor_movie（foreign column）为空。

场景2：与电影

相关联的演员我也试过这样：

public class HibernateTest { 

     public static void main(String[] args) { 

    Movie movie = new Movie("Titanic", new Date(1997,12,19)); 
     Actor actor1=new Actor("Leo"); 
     Actor actor2=new Actor("Kate"); 
     actor1.setMovie(movie); 
     actor2.setMovie(movie); 

     SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory(); 
      Session session = sessionFactory.openSession(); 
      session.beginTransaction(); 
      session.persist(movie1); 
      session.getTransaction().commit(); 
      session.close(); 
} 
} 

在这里，我看到在一排在影片表坚持的数据库，但没有行被演员坚持表。

我不明白为什么这两种情况都会失败？请提供解释为什么它会出错？

非常感谢

Answer 1

至于有电影和演员之间的双向关联，你必须设定两个彼此。

方案1个

public class HibernateTest { 

    public static void main(String[] args) { 

      Movie movie1 = new Movie("Mr and Mrs.Smith", new Date(2005, 6, 5)); 
      Actor actor3=new Actor("Brad"); 
      actor3.setMovie(movie1); // Missing in ur code 
      Actor actor4=new Actor("Joe"); 
      actor4.setMovie(movie1); // Missing in ur code 
      movie1.getActors().add(actor3); 
      movie1.getActors().add(actor4); 

     SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory(); 
     Session session = sessionFactory.openSession(); 
     session.beginTransaction(); 
     session.persist(movie1); 
     session.getTransaction().commit(); 
     session.close(); 

    } 
} 

方案2

public class HibernateTest { 

     public static void main(String[] args) { 

    Movie movie = new Movie("Titanic", new Date(1997,12,19)); 
     Actor actor1=new Actor("Leo"); 
     Actor actor2=new Actor("Kate"); 
     actor1.setMovie(movie); 
     actor2.setMovie(movie); 
     movie.getActors.add(actor1); // missing in ur code 
     movie.getActors.add(actor2); // missing in ur code 

     SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory(); 
      Session session = sessionFactory.openSession(); 
      session.beginTransaction(); 
      session.persist(movie1); 
      session.getTransaction().commit(); 
      session.close(); 
} 

} 

希望这有助于。

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