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another mock exam question

madhav changala
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Joined: Dec 20, 2005
Posts: 57
Consider the following JSP code (See exhibit).What will it print for the very first request to this page as well as the web application that contains this page?

<html><body><% Integer count = (Integer) request.getSession(false).getAttribute("count"); if(count != null ) { out.println(count); } else request.getSession(false).setAttribute("count", new Integer(1));%>Hello!</body></html>

Select 1 correct option.
A.It will print Hello!
B.It will print Hello and will set the count attribute in the session.
C.It will throw a NullPointerException at request time.
D.It will not compile.


My answer was C.. as request.getSession(false) returns null at the very first request.. as null.set/getAttribute() results.. NullPointerexception.. right? But the answer given is B..

Could any help on this?

ThanksInAdvance


saivenumadhav
Joe Harry
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Joined: Sep 26, 2006
Posts: 9345
    
    2

Even I guess that the answer is C!


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Srinivasan thoyyeti
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Joined: Feb 15, 2007
Posts: 557
I will go for B. Why because by default session(Page Directive)=true is created for JSP.


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Joe Harry
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Joined: Sep 26, 2006
Posts: 9345
    
    2

Madhav, did you actually try this out??? I don't have a system to try it or otherwise I would have done it practically and checked!
Paul Anilprem
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Joined: Sep 23, 2000
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    2
Hi Madhav,
Did you see the detailed explanation that is provided with it?


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Manju Devarla
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Joined: Dec 14, 2006
Posts: 85
it prints Hello! no Nullpointer exception
achayya matta
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Joined: Oct 27, 2005
Posts: 111
Yes, it prints hello for the first request and "1 hello" for the next request.
madhav changala
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Joined: Dec 20, 2005
Posts: 57
I did n't try out this one..

But there was no detailed answer...

Could any one from above tell how hello will be the correct answer?

ThanksInadvance
Rishi Chopra
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Joined: Mar 07, 2004
Posts: 108
hi,

Since the question has not specified the page directive in the code snippet .. so the jsp container assumes that the page directive has session set to true.So a jsp page automatically participates in session tracking.
when
<% Integer count = (Integer) request.getSession(false).getAttribute("count");
is encounteres then the session is already there so "request.getSession(false)" wud return the session created implicitly by the page but there is no attribute named count so above statement is equal to Integer count=null;

then the code enters the else clause where the count is set as an attribute with value as new Integer(1) and then Hello is printed..

I hope i am able to clear your confusion

Regards
Rishi Chopra


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Niranjan Deshpande
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Joined: Oct 16, 2005
Posts: 1277
yes rishi you are...


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