Exceptions question

[amol deshpande]

Hi there, HFEJB says the if a client calls remove on bean thats already removed, you will get RemoteException or EJBException....(r Vs l ).

But I tried on entity as well as session bean...
...my client code is like this

1)Entity...

address.remove();
// now address bean is removed....address is remote component interface

// now i call remove again.
address.remove();

this gives me NoSuchObjectException

2) Session

counter.remove();
// now counter session is removed
//now i call remove again

counter.remove();

this gives me NoSuchObjectException

Now under what situation does calling remove on already removed bean gives Remote or EJB exception?

I think there is a good reason why I'm getting NoSuchObjectException...
when we call remove first, ejbobject dies on server...next time there is no such ejbobject to serve our remove...so its pretty acceptable.

Please clarify me if i'm missing something....
Amol

[Gian Franco]

Hi Amol,

I don't have HF EJB with me, but I recal reading something
about the vendor being free to throw more or less specific
Remote exceptions.

In this case for NoSuchObjectException (which extends RemoteException)
the vendor of your container has implemented it in order to
give you back more detailed info, another vendor might chose
to give back only RemoteException.

When I get hold of the book I'll try to confirm the above, unless
someone else reads this first

Cheers,

Gian

[amol deshpande]

Hi there,
First of all thank you very much for considering a reply.

Yeah I also went through the Spec and HFEJB which says container is free to choose if it wants to give more specific exception.
But I thought it was talking in context of exceptions like DuplicateKeyException which is a subclass of CreateException and ObjectNotFoundException which is subclass of FinderException.

But container must thorow NoSuchObjectException if there is no object for stub by client side.(I think).

Do you mean that my container is throwing me more Specific exception here? (NoSuchObjectException being subclass of RemoteException.)

May be your right.....but I still cant help fixin it up !!!
Please clarify my view.

Amol.

[Gian Franco]

Hi Amol,

I got back home and got hold of the book

You're right when you say

... container is free to choose if it wants to give more specific
exception. But I thought it was talking in context of exceptions
like DuplicateKeyException which is a subclass of CreateException
and ObjectNotFoundException which is subclass of FinderException.

(see HF EJB p.550)

So what I've said in the previous post is not correct . Throwing
the NoSuchObjectException is a requirement of the spec.

In the EJB specs (18.4.2.3) it says:

The java.rmi.NoSuchObjectException is a subclass of the java.rmi.RemoteException.
It is thrown to the client if a remote business method
cannot complete because the EJB object no longer exists.

and

When the client calls remove on the home or component interface to remove
the session object, the container issues ejbRemove() on the bean instance.
This ends the life of the session bean instance and the associated session
object. Any subsequent attempt by its client to invoke the session object
causes the java.rmi.NoSuchObjectException to be thrown if the client is a
remote client, or the javax.ejb.NoSuchObjectLocalException if the client is
a local client. (The java.rmi.NoSuchObjectException is a subclass of the
java.rmi.RemoteException; the javax.ejb.NoSuchObjectLocalException is a
subclass of the javax.ejb.EJBException). The ejbRemove() method cannot be
called when the instance is participating in a transaction. An attempt to
remove a session object while the object is in a transaction will cause the
container to throw the javax.ejb.RemoveException to the client. Note that a
container can also invoke the ejbRemove() method on the instance without a
client call to remove the session object after the lifetime of the EJBobject has expired.

(see EJB spec 7.6.0)

I think that when HF EJB says you will get a RemoteException or a
EJBException is technically correct, since these are superclasses
of the more specific exceptions NoSuchObjectException and
NoSuchObjectLocalException. But according to the specs I'd say
the HF statement is not precise enough

What do you think?

Gian
[ March 10, 2005: Message edited by: Gian Franco Casula ]

[amol deshpande]

HI there,
Again I must thank you for keeping on the discussion!!!
In HFEJB,(I dont have book in hand , I'm in cafe)Ch. of Exceptions, there is a question in chapter(not chapter mock exam) which gives scenarios and in next column, lots of exceptions are also given which includes all Application(5) exceptins and System Exceptions too.
But in answer it gives the RemoteException & EJBException as answers....while solving the exercise I selected NoSuchObjectException/local but I was wrong according to HFEJB.
......so now as you said HFEJB is not wrong but just not more specific in selecting its answer....but what if you are already given NoSuchObjectException in options too?
Amol.

[Gian Franco]

Hi Amol,

I've got HF right next to me now.

I see what you mean, the question can put one
in a dilemma for what to chose. In order to give
a consistent reply to the HF question, I guess
saying the answer is RemoteException and
EJBException is the best reply in this case.

Why? Because, since the client can be both remote
and local (it's not specified in the question) the
real exceptions thrown by the container are
NoSuchObjectException and NoSuchObjectLocalException.
These respecively implement RemoteException and EJBException.

Since NoSuchObjectLocalException is not provided as an
answer, I'd say ticking both superclasses would be best

Cheers,

Gian