lazy initialization leads to org.hibernate.LazyInitializatio

[lindner]

I have two entity Beans. Both associated in a OneToMany relation.
Bean A is The parent bean.
Bean B is the child bean that holds a reference to A like this:

class BeanB ....
private BeanA a;
@ManyToOne(
fetch=FetchType.LAZY,
optional=false
)
@JoinColumn(
name="a",
nullable=false
)
public BeanA getA() {
return a;
}

public void setA(BeanA a) {
this.a = a;
}

Now on a client I retrieve on instance of BeanB. Whe I try to access elements of A like

BeanB b = controller.find...
b.getA().getId()

the followin exception occurs:

org.hibernate.LazyInitializationException
could not initialize proxy - no Session
org.hibernate.LazyInitializationException: could not initialize proxy - no Session
at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:53)
at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:98)
at org.hibernate.proxy.CGLIBLazyInitializer.intercept(CGLIBLazyInitializer.java:158)
...

I understand that BeanB is detached from the transaction context and behind the scene a database transactionis needed to load BeanA. But how can I manage this on a client?
I tried to put a transaction around the call

UserTransaction ut = (UserTransaction)(ctx.lookup("UserTransaction"));
ut.begin();
BeanB b = controller.find...
b.getA().getId()
ut.commit();

buth the result is the same? What can I do?

[cyril.joui]

Hello,

You must initialize all lazy relation on EJB container before using them on the client !

Try to do, in method find...() {
BeanB b = em.find(BeanB.class, id);
// intialize A !
b.getA().getId()

return b;

}

The client if out of the EJB container ...

[lindner]

Hello Cyril,

but what is lazy loading good for if I alwayas have to preload lazy attributes bevore transfering them to the client? Is there now way to do this on demand in an elegant way? Some frameworks? Some design patterns?

[lindner]

There must be some sort of interceptor that does the lazy loading. Isn't it possible to modify this interceptor? If I understand the ejb specification correctly, custom interceptors are only possible for session and message beans, not for entity beans.

[epbernard]

The framework you're looking for is JBoss Seam