EJB 3.0 indirection problem

Question

Hi,
I'm trying to use lazy loading with EJB 3.0. I've generated CMP beans from tables in JDev. I have the same table schema as in tutorial:
http://www.oracle.com/technology/tech/java/oc4j/ejb3/howtos-ejb3/howtooutofcontainer/doc/how-to-ejb30-out-of-container.html
I have such a mapping:
@ManyToOne(fetch=EAGER)
@JoinColumn(name="CUST_ID", referencedColumnName="EJB_CUSTOMER.CUST_ID")
public EjbCustomer getEjbCustomer() {
return ejbCustomer;
It works fine, but when I change the value of "fetch" attribute to LAZY a get following Exception:
java.lang.NullPointerException
     at oracle.toplink.internal.indirection.UnitOfWorkValueHolder.instantiate(UnitOfWorkValueHolder.java:205)
     at oracle.toplink.internal.indirection.DatabaseValueHolder.getValue(DatabaseValueHolder.java:61)
     at ejb_sample.EjbOrder.getEjbCustomer(EjbOrder.java:72)
     at ejb_sample.EjbSampleFacadeEJBClient.main(EjbSampleFacadeEJBClient.java:29)
Do I have to set anything else (more thane "fetch" attribute) to use indirection?
Thanks for any reply,
Piotr Bloch
Poznan Univerity of Technology, Poland

Answer 1

Piotr,
I assume from your stack trace that you are accessing the attribute on a remote client. When a JPA entity is returned from a remote session bean it is serialized. When this happens any non-instantiated relationships will no longer be able to trigger the lazy load capability as they are now detached from the persistence context of the server.
If you require lazy-loaded relationships on the client it is recommended that you trigger their loading on the server prior to returning them.
Doug