Re: Catching exceptions in JPL

Thanks, Ed.

I guess I should have examined the JPL code more closely because I was
unaware that  ExceptionOccured(), ExceptionDescribe(), and ExceptionClear()
existed.  I tried a little test and it worked...sort of.  The problem is
that if the exception occurs in the Java (duh!) then the JPL::AutoLoader
fails because it doesn't get a valid ref to bless.  This is the point where
the Perl dies.  So, my exception handling code never has a chance to run
because Perl bails out deep within the bowels of JPL.

Thanks for the suggestion though.  I has me thinking about a possible patch
to JPL that will allow exception handling within the JPL::AutoLoader.

Cheers,
Scott.

====================================================
M. Scott Roth,
<[email protected]>
Information Systems Engineer
Science Applications International Corporation
703-375-2260
========================<><=========================



                                                                                                     
                    Ed Chidester                                                                     
                    <echid@textwi        To:     [email protected], [email protected]              
                    se.com>              cc:                                                         
                                         Subject:     Re: Catching exceptions in JPL                 
                    11/07/00                                                                         
                    04:55 PM                                                                         
                    Please                                                                           
                    respond to Ed                                                                    
                    Chidester                                                                        
                                                                                                     
                                                                                                     





>
> Does anyone know of a way to catch a Java exception from JPL?  For
example,
> I have a login method in Java that throws an exception if the login fails
> for any number of reasons.  I have JPL code that calls the login method
> from Perl but since the method is a void method, I get no return value to
> evaluate for success or failure.  The login code is not mine or I would
> change it to return a boolean just for this reason.
>
...
>
> Any ideas would be appreciated.  Thanks!
>

You said 'any' ideas, but I'm going to start by saying that this is an
incomplete (and possibly wrong) idea... Also, I'm still in the early stages
of using JPL

Now that my disclaimer is finished, here's my idea:


Java's JNI has method calls to catch, describe, and remove Java exceptions
from within native code  (ExceptionOccurred, ExceptionDescribe, and
ExceptionClear respectively).  Looking at the JNI/JNI.xs source I see
these same methods wrapped in xs code. You might be able to do something
like this:


     use JNI;

     $username = "me\\you\@thisplace.com";
     $login = JPL::AutoLoader::getmeth('login',['java.lang.String'],[]);
     &$login($username);

     if ( ExceptionOccurred( ) ) {
         ExceptionDescribe( );
         ExceptionClear( );
     }

Of course, ExceptionOccurred( ) returns an object of type "jthrowable" so
I'm not entirely sure how that'll be handled.


Hope this helps!


Ed.


// Edward Chidester
// Software Engineer                            MNIS - Textwise Labs
// (315) 426-9311 x232                          401 South Salina Street
// [email protected]                           Syracuse, NY 13202