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From "DHarty" <>
Subject RE: JSP, JNI, classloader
Date Wed, 20 Jun 2001 21:33:17 GMT
I had many similar problems with JNI a while back.  I don't remember all the
details, but I remember that for some reason, any Java class that used JNI
could NOT be in a package.

I don't know if they ever provided a fix to this, but I removed all package
info from my JNI related java files, and everything began to work.

Good luck.


-----Original Message-----
From: Matthew Lerner []
Sent: Wednesday, June 20, 2001 4:41 PM
Subject: JSP, JNI, classloader

Apologies for being a clueless newbie, but I've been beating my head on
this for the last week.

I'm setting up a new webapp.  It needs to interact with a C++
library.  (There are reasons it needs to be in C++.  Really there
are.)  Since I've never done JSP or JNI before, I figured I'd get a
skeletal application going - all I'm trying to do is have a .jsp page
communicate with a C library.  So first I thought I'd better set up a Java
Bean and get my jsp talking to that, and then maybe I can see about talking
to JNI.  That first part went great.  Since I'd had trouble with it before,
I very carefully verified that recreating my .class file (in
ROOT/WEB-INF/classes) actually modified my bean.  I even managed to use
both get and set methods.  All was going well.

Then I added the native interface code to the bean:
     public native int getInt(int arg);

     static {

I'd tested this code in a normal java application, and it worked
fine.  When I tried to load the Bean from JSP though, not only did it not
work (I failed to copy the error message, sorry), but it stopped reloading
the class when I recompile it.  Restarting Tomcat did not help.

So, first things first -- how do I get Tomcat to see new versions of the

After that, anybody have pointers on how to get JSP to talk to JNI?

Thanks in advance
	Matthew Lerner

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