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From Jim Cheesman <>
Subject Instantiating/declaring classes in JSP (Was: simple question)
Date Fri, 20 Jul 2001 07:00:04 GMT
At 11:55 PM 19/07/01, you wrote:
(And could you possibly use a more descriptive title in future? "Simple 
question" could be anything, and a lot of people would delete it 
immediately without reading...)

>I know this is somewhat off topic, but I have looked everywhere and can't
>find the answer to this simple question...
>Is there a way to test and see whether a variable has been instantiated and
>if it hasn't, instantiate it?

Object myObject;

if (myObject == null) {
         myObject = new Object();


>My problem is that I am working on an application that makes use of jsp's
>that are included inside many others.  I want to use a bean, but if I call
>it by a different name in every spot, then they don't share information.  If
>I use the same name, and the containing jsp has already declared that it is
>using the bean, then it gives me an error and says it has already been
>declared.  Any ideas on how I can get around this?  Thank you in advance for
>any help!!!

Ah! A different question...

Try jsp:usebean... If the bean is declared, it'll use it. If not, it'll 
instantiate a new one.

If you want to know whether you've instantiated it, or if you are reusing a 
previously instatiated class, it's a bit more difficult. The only way I can 
think of is by setting a variable internally on instantiation and checking 
that. Of course, you'd have to ensure that all the developers do the same 



                           *   Jim Cheesman   *
             Trabajo: - (34)(91) 724 9200 x 2360
                       One should 
never generalize.

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