@Entity
@Table(name = "item_author_role")
public class ItemAuthorRole implements Serializable {
  @Getter @Setter @EmbeddedId
  private ItemAuthorRoleId id;
  @Setter private Item item;

  @MapsId("itemId")
  @ManyToOne(fetch = FetchType.LAZY)
  @JoinColumn(name = "item_id", referencedColumnName = "item_id")
  public Item getItem()               { return item; }
 
 @Override
  public boolean equals(Object obj) {
    if(obj instanceof ItemAuthorRole) {
      ItemAuthorRole role = (ItemAuthorRole) obj;
      return role.getItem().equals(item);
    }
    return false;

  }

  @Override
  public int hashCode() {
    return new HashCodeBuilder(17, 31).append(item).toHashCode();
  }
}

@Embeddable
class ItemAuthorRoleId implements Serializable {
  @Getter @Setter @Column(name = "item_id", nullable = false)
  private int itemId;

  @Override
  public boolean equals(Object obj) {
    if(obj instanceof ItemAuthorRoleId) {
      ItemAuthorRoleId id = (ItemAuthorRoleId) obj;
      return id.itemId == itemId;
    }
    return false;

  }
  @Override
  public int hashCode() {
    return new HashCodeBuilder(17, 31).append(itemId).toHashCode();
  }
}

@Entity
@Table(name = "items")
public class Item extends AbstractModel implements Serializable {
  @Setter private Set<ItemAuthorRole> itemAuthorRoleSet;
  @Setter private Technic technic;

  {
    itemAuthorRoleSet = new HashSet<>(0);
  }

  @Override
  @SequenceGenerator(name = "isg", sequenceName = "item_sequence", initialValue = 1, allocationSize = 2)

  @Id
  @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "isg")
  public Integer getId()                               { return super.getId(); }

  @JoinColumn(name = "item_id", insertable = false, updatable = false) //no effect 
  @OneToMany(fetch = FetchType.LAZY, cascade = {CascadeType.DETACH}, mappedBy = "item", targetEntity = ItemAuthorRole.class)
  public Set<ItemAuthorRole> getItemAuthorRoleSet()    { return itemAuthorRoleSet; }

  @OneToOne
  @JoinColumn(name = "technic_id")
  public Technic getTechnic()                          { return technic; }

  @Version
  @Column(name = "opt_lock")
  private Long version;
}

Exception [EclipseLink-48] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.DescriptorException
Exception Description: Multiple writable mappings exist for the field [item_author_role.item_id].  Only one may be defined as writable, all others must be specified read-only.
Mapping: org.eclipse.persistence.mappings.OneToOneMapping[item]
Descriptor: RelationalDescriptor(model.item.ItemAuthorRole --> [DatabaseTable(item_author_role)])

  @Setter private Item item;

  @MapsId("itemId")
  @ManyToOne(fetch = FetchType.LAZY)
  @JoinColumn(name = "item_id", referencedColumnName = "item_id")
  public Item getItem()               { return item; }

  @MapsId("itemId")
  @ManyToOne(fetch = FetchType.LAZY)
  @JoinColumn(name = "item_id", referencedColumnName = "item_id")
  @Setter @Getter private Item item;

  @MapsId("itemId")
  @ManyToOne(fetch = FetchType.LAZY)
  @JoinColumn(name = "item_id", referencedColumnName = "item_id")
  @Setter private Item item;

  public Item getItem()               { return item; }