mock question about interceptor of EJB3.0

[Sam Sunamin]

The following is the mock question about interceptor, I am not sure about the questions, please help me.

A developer writes an interceptor class called FooInterceptor containing the following AroundInvoke method:
 
11. @AroundInvoke
12. public Object Intercept(InvocationContext ctx){
13.  return "intercpted";
14. }
 
FooInterceptor is applied to a business method in a stateless seesion bean:
11. @Interceptors(FooInterceptor.class)
12. public String testzero(int i){
13. return (i==0)? "zero": "not zero";
14. }
 
Which describes the result when a client invokes the testzero method with a value of 1?
 A - The intercept method is NEVER invoked.
 B - The client receives a return value of "zero".
 C - The client receives a return value of "not zero".
 D - The client receives a return value of "intercepted".

[ August 29, 2007: Message edited by: Sam Sunamin ]
[ September 07, 2007: Message edited by: Sam Sunamin ]

[Benoît de Chateauvieux]

The client will always receives a return value of "intercpted".
The methos testzero is not invoked.

I don't know what's the good answer because the answer D is:
D - The client receives a return value of "intercepted".
and the return of the method Intercept is "intercpted".

I hope it's a copy error and the exam don't test on it.

Beno�t

[Camilo Morales]

I think the interceptor method will never be invoked because the method signature is wrong:

According MZ Notes:

AroundInvoke methods have the following signature:

Object <METHOD>(InvocationContext) throws Exception

The exception throw is missing.

Please confirm if this is correct,

[Narendra Dhande]

Hi,

The testzero method is not invoked because the interceptor method does not contain the ctx.proceed(); statement. Due to this reason, the next method in the chain, that is testzero business method is never invoked.

Thanks

[Benoît de Chateauvieux]

Hi Camilo,

When I test the following code in my OC4J

    @AroundInvoke
    public Object Intercept(InvocationContext ctx){
        try {
            return "In interceptor > "+ctx.proceed();
        } catch (Exception e) {
            return null;
        }
    }

it returns

In interceptor > zero

So I think that the interceptor method is invoked even if there's no throw Exception.
But I know that, in some points, OC4J doesn't follow the EJB specifications.

Thanks

[Narendra Dhande]

Hi,

The interceptor method can throw Exception. That is can can throw any checked Exception and run-time Exception. Also, If the interceptor method can throw only the Exception which are defined in the business method.

This mean that the interceptor method can be without throws clause, if the exceptions are handles internally in the method.

Your example is running perfectly. I think OC4J container is Java EE compliant with some extra facilities.

Thanks

[Camilo Morales]

Alright Beno�t and Narendra ,,, thanks for clarifying.

Regards,

[Sam Sunamin]

The answer for this is D, return intercepted.

Now, I know why.

Since the overrided interceptor can swallow the exception and it has no ctx.proceed() called.

Best regards.