• Post Reply Bookmark Topic Watch Topic
  • New Topic
programming forums Java Mobile Certification Databases Caching Books Engineering Micro Controllers OS Languages Paradigms IDEs Build Tools Frameworks Application Servers Open Source This Site Careers Other Pie Elite all forums
this forum made possible by our volunteer staff, including ...
Marshals:
  • Campbell Ritchie
  • Ron McLeod
  • Paul Clapham
  • Jeanne Boyarsky
  • Liutauras Vilda
Sheriffs:
  • Rob Spoor
  • Bear Bibeault
  • Tim Cooke
Saloon Keepers:
  • Tim Moores
  • Stephan van Hulst
  • Tim Holloway
  • Carey Brown
  • Piet Souris
Bartenders:
  • Frits Walraven
  • Himai Minh

Page 168 :)

 
Ranch Hand
Posts: 385
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
"Given a remote client 'R', that has valid references to session beans 'A' and 'B', and given that A is local to B, which statements are true?
Amongst others I chose:
A. R cannot pass his reference for A, to B.
And that was wrong. And I dont know why. R client passes reference of remote A to remote B then the serialized stub is sent. But what the use of the stub A to the bean B which is local to A? And if B expects that A is local to him all those bad things may happen (like treating arguments as real references instead of copies, exceptions etc).
Another day another tough question...
 
Vladas Razas
Ranch Hand
Posts: 385
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
I am so sad nobody looks in my questions
 
Bartender
Posts: 1872
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Hi Vladas,

I am so sad nobody looks in my questions.


I understand that sort of frustration !
If nobody answers to you, I guess that nobody who read it felt comfortable with your question. Kathy, Bert or Valentin should be back soon or later ...
BTW, you'd make a good advertiser !
Back to the question :


Given a remote client 'R', that has valid references to session beans 'A' and 'B', and given that A is a local client to B, which statements are true? (Choose all that apply.)
A. R cannot pass his reference for A, to B.
X B. A cannot pass his reference for B, to R.
C. A cannot invoke methods on B.
X D. B cannot invoke methods on R.


Correct answers are B and D.
The book's explanation ("You can't give a remote client a local reference, A sees B through a local reference") explains B (A's reference to B is local and R is a remote client).
C. is easy : A is a local client of B, so it can invoke methods on B.
D. is easy too : B is the remote target in the R/B remote relationship. EJB doesn't support callbacks to the remote client.
I think with you that A is more subtle, because it all turns around the verb used : "pass". R having a remote reference to A, it can pass it to its remote client B. So answer "A" must stay unchecked. But would it make sense ? (I think that's your question). Put in other words, will B be able to do anything useful with a remote reference to A ? Given the question, we don't know. B should be a remote client to A (not stated in the question), having a remote reference to A defined in the DD (<ejb-ref> element), which is neither stated in the question. So yes, R can pass his reference to B. While what B can (or cannot) do with it we simply don't know from the question.
Kathy, if you read this, please comment.
Best,
Phil.
[ December 07, 2003: Message edited by: Philippe Maquet ]
 
You showed up just in time for the waffles! And this tiny ad:
Building a Better World in your Backyard by Paul Wheaton and Shawn Klassen-Koop
https://coderanch.com/wiki/718759/books/Building-World-Backyard-Paul-Wheaton
reply
    Bookmark Topic Watch Topic
  • New Topic