Problem with ManyToMany and JPA EclipseLink

I've got a ManyToMany Relationship with composite key between a User and a Group in JPA EclipseLink. My Implementation looks like that:

User Class:

@Entity
@Table(name="mbm_user")
public class User extends CanAccessBook{

@Id @GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(nullable = false)
private Long id;

@OneToMany(mappedBy="user",cascade=CascadeType.PERSIST)
private List<GroupMembership> groups = new ArrayList<GroupMembership>();

  /**
   GETTER & SETTER
  **/
}

Group Class:

@Entity
@Table(name="mbm_group")
public class Group extends CanAccessBook{

@Id @GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(nullable = false)
private Long id;

@OneToMany(mappedBy="group", cascade=CascadeType.PERSIST)
private List<GroupMembership> users = new ArrayList<GroupMembership>();

  /**
   GETTER & SETTER
  **/
}

GroupMembership Class:

@Entity
@Table(name = "group_user")
@IdClass(UserGroupPK.class)
public class GroupMembership {

@Id
@ManyToOne
@PrimaryKeyJoinColumn(name="USERID")
private User user;

@Id
@ManyToOne
@PrimaryKeyJoinColumn(name="GROUPID")
private Group group;

@Temporal(TemporalType.DATE)
private Date joinedAt = new Date();

@Temporal(TemporalType.DATE)
private Date validUntil;

  /**
   GETTER & SETTER
  **/
}

UserBookPK Class:

public class UserBookPK{

@Id
@Column(name="BOOKID")
private Long book;

@Id
@Column(name="USERID")
private Long user;

public Long getBook() {
    return book;
}

public void setBook(Long book) {
    this.book = book;
}

public Long getUser() {
    return user;
}

public void setUser(Long user) {
    this.user = user;
}
}

My JUnit Tests are report no errors, but if I test it on my Tomcat, I'm getting the following errors

Exception [EclipseLink-59] (Eclipse Persistence Services - 2.1.1.v20100817-r8050): org.eclipse.persistence.exceptions.DescriptorException Exception Description: The instance variable [groupId] is not defined in the domain class [de.kapieren.mbm.server.model.GroupMembership], or it is not accessible. Internal Exception: java.lang.NoSuchFieldException: groupId Mapping: org.eclipse.persistence.mappings.DirectToFieldMapping[groupId-->group_user.GROUPID] Descriptor: RelationalDescriptor(de.kapieren.mbm.server.model.GroupMembership --> [DatabaseTable(group_user)])

Exception [EclipseLink-59] (Eclipse Persistence Services - 2.1.1.v2开发者_运维问答0100817-r8050): org.eclipse.persistence.exceptions.DescriptorException Exception Description: The instance variable [userId] is not defined in the domain class [de.kapieren.mbm.server.model.GroupMembership], or it is not accessible. Internal Exception: java.lang.NoSuchFieldException: userId Mapping: org.eclipse.persistence.mappings.DirectToFieldMapping[userId-->group_user.USERID] Descriptor: RelationalDescriptor(de.kapieren.mbm.server.model.GroupMembership --> [DatabaseTable(group_user)])

Exception [EclipseLink-0] (Eclipse Persistence Services - 2.1.1.v20100817-r8050): org.eclipse.persistence.exceptions.DescriptorException Exception Description: An internal error occurred accessing the primary key object [202]. Internal Exception: java.lang.NoSuchFieldException: groupId Descriptor: RelationalDescriptor(de.kapieren.mbm.server.model.GroupMembership --> [DatabaseTable(group_user)])

Whats going wrong here?

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You should be using @JoinColumn instead of @PrimaryKeyJoinColumn for the @ManyToOnes.

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I tried the exactly same code with a windows machine and it works without problems. I think the problem is the JVM of MAC OS (I'm working with Mac OS). So I have to continue my work on a windows VM. this issue seems to be documented by EclipseLink (Exception 59). This is very bad for me and I think this will be my Last time I gave Java a try....

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You have a UserBookPK class, but it's not referenced anywhere else. I assume this is supposed to be UserGroupPK? In which case it is wrong. The fields should be instances of User and Group, for one. It should be Serializable (but not include a version id, for some reason).

Better yet, don't use @IdClass at all. It's only there for backwards compatibility. Put a surrogate key on GroupMemberShip and use that to link everything together. Or if you really want the composite primary key, go for an @EmbeddedId. Since this is just the relationship modelled as object, that does make some sense.

You don't necessarily need to map the intermediate class either, there is an @ManyToMany that sometimes works.