Hey guys,
I've found a bug in the "Compound Primary Keys" implementation in JBoss/Hibernate EJB3. I've been able to reproduce this problem on JBoss 4.0.4GA and jboss-EJB-3.0_Embeddable_ALPHA_9. Current implementation generates extra field from compound key. This is an example from Sun's "The Java EE 5 Tutorial" http://java.sun.com/javaee/5/docs/tutorial/doc/PersistenceEJB2.html

@IdClass(order.entity.LineItemKey.class)
@Entity
@Table(name = "EJB_ORDER_LINEITEM")
public class LineItem {
 @Id
 public int getItemId() {
 return itemId;
 }
 @Id
 @Column(name="ORDERID", nullable=false, insertable=false, updatable=false)
 public Integer getOrderId() {
 return orderId;
 }
}

public final class LineItemKey implements java.io.Serializable {

 private Integer orderId;
 private int itemId;
...
 public Integer getOrderId() {
 return orderId;
 }
...
}

This generates following SQL in logs:

DEBUG [org.hibernate.persister.entity.AbstractEntityPersister] Snapshot select: select lineitem_.orderId, lineitem_.itemId, lineitem_.ORDERID as ORDERID9_, lineitem_.quantity as quantity9_, lineitem_.VENDORPARTNUMBER as VENDORPA4_9_ from EJB_ORDER_LINEITEM lineitem_ where lineitem_.orderId=? and lineitem_.itemId=?
DEBUG [org.hibernate.persister.entity.AbstractEntityPersister] Insert 0: insert into EJB_ORDER_LINEITEM (ORDERID, quantity, VENDORPARTNUMBER, orderId, itemId) values (?, ?, ?, ?, ?)
DEBUG [org.hibernate.persister.entity.AbstractEntityPersister] Update 0: update EJB_ORDER_LINEITEM set ORDERID=?, quantity=?, VENDORPARTNUMBER=? where orderId=? and itemId=?
DEBUG [org.hibernate.persister.entity.AbstractEntityPersister] Delete 0: delete from EJB_ORDER_LINEITEM where orderId=? and itemId=?

OR

insert into EJB_ORDER_LINEITEM (ORDERID, quantity, VENDORPARTNUMBER, orderId, itemId) values (?, ?, ?, ?, ?)

As you can see there are duplicationg columns: ORDERID from LineItem class and orderId from LineItemKey.
When I add @Column annotation to the LineItemKey:

public final class LineItemKey implements java.io.Serializable {

 private Integer orderId;
 private int itemId;
...
 @Column(name="ORDERID", nullable=false, insertable=false, updatable=false)
 public Integer getOrderId() {
 return orderId;
 }
...
}

I got exception:

org.hibernate.MappingException: Repeated column in mapping for entity: order.entity.LineItem column: ORDERID (should be mapped with insert="false" update="false")
 at org.hibernate.mapping.PersistentClass.checkColumnDuplication(PersistentClass.java:575)

I believe this is connected to Hibernate bug HBX-164 http://opensource.atlassian.com/projects/hibernate/browse/HBX-164
Should I file a bug to JBoss or Hibernate JIRA?