How to set up a many-to-many relationship with a navigation table using JPA / EclipseLink

Question

I have 2 tables:

Movies: movieID

Users: user id

These tables have a many-to-many relationship through the Queue table, an additional attribute, listOrder:

Queue: movieID, User ID, listOrder

I am trying to simulate this using EclipseLink, but I am getting an "incompatible display" error. Here is an example of my code:

@Entity
@Table(name="movieinventory")
public class Movie implements Serializable
{
       private static final long serialVersionUID = 1L;

       @Id
       @GeneratedValue
       private Integer movieID;

       @OneToMany(mappedBy="movie")
       private Set moviesInQueue;

       ...Getters/Setters...
}

@Entity
@Table(name="Users")
public class User implements Serializable
{
       private static final long serialVersionUID = 1L;

       @Id
       @GeneratedValue
       private Integer userID;

       @OneToMany(mappedBy="user")
       private Set moviesInQueue;

      ...Getters/Setters...
}

@IdClass(QueueItemPK.class)
@Entity
@Table(name="queue")
public class QueueItem
{
       @Id
       @ManyToOne
       @JoinColumn(name="movieID")
       private Movie movie;

       @Id
       @ManyToOne
       @JoinColumn(name="userID")
       private User user;

       @Basic
       private String listOrder;

       ...Getters/Setters...
}

public class QueueItemPK implements Serializable
{
       private static final long serialVersionUID = 1L;

       private Movie movie;
       private User user;

       ...Getters/Setter...

       public int hashCode()
       {
           return (movie.getMovieID() + "|" + user.getUserID()).hashCode();
       }

       public boolean equals(Object obj)
       {
           if (obj == this) return true;
           if (obj == null) return false;
           if (!(obj instanceof QueueItemPK)) return false;
           QueueItemPK pk = (QueueItemPK) obj;
           return pk.movie.getMovieID() == movie.getMovieID() 
               && pk.user.getUserID() == user.getUserID();
       }
}

The goal of QueueItemPK is that I can have a composite primary key from movieID and userID. I'm not quite sure if this is the right way to go.

: : [class Movie] [class QueueItem]. , backpointer. User ( ).

@Id QueueItem , .

.

, B.J.

Answer 1

, , EmbeddedId/Class, , . , :

@IdClass(QueueItemPK.class)
@Entity
@Table(name="queue")
public class QueueItem
{
       @Id
       @ManyToOne(optional=false)
       @PrimaryKeyJoinColumn(name="movieID")
       private Movie movie;

       @Id
       @ManyToOne(optional=false)
       @PrimaryKeyJoinColumn(name="userID")
       private User user;

       @Basic
       private String listOrder;

       ...Getters/Setters...
}

public class QueueItemPK implements Serializable
{
       private static final long serialVersionUID = 1L;

       @Id
       @Column(name="movieID")
       private Integer movie;
       @Id
       @Column(name="userID")
       private Integer user;

       ...Getters/Setter...

       public int hashCode()
       {
           return (movie.getMovieID() + "|" + user.getUserID()).hashCode();
       }

       public boolean equals(Object obj)
       {
           if (obj == this) return true;
           if (obj == null) return false;
           if (!(obj instanceof QueueItemPK)) return false;
           QueueItemPK pk = (QueueItemPK) obj;
           return pk.movie == movie 
               && pk.user == user;
       }
}

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