UnsatisfiedLinkError upon System.load() of library even though the load is in the init() function of the servlet.

Question

All,
Any help on this would be appreciated. We have a servlet that calls a native method
and we load the native library in the servlet's 'init()' method so the servlet
gets loaded only once. However, periodically, I get the following error:
java.lang.UnsatisfiedLinkError : Native Library /opt/shared2/weblogic/myserver/servletclasses/twtc/servlet/toc/toclib.so
already loaded in another classloader
It seems to bring down weblogic when this happens.
Why does this happen?
Is there a way around this?
As a test, I called System.load() 10 times outside of the init function with the
same library and it did not fail once but it does periodically in the init() function
of my servlet, which implies that the init function is being called more than
once.

Answer 1

Like what the error message says, you can only load a native library once per ClassLoader per VM.
You can test this by constructing two ClassLoaders and loading the same library.
The reason why a servlet will be constructed by different classloaders with a VM session is if:
1) the servlet is reloaded (hot-deployed)
2) the servlet belongs in more than one ear, since each ear has its own classloader.
Gene
"Michael" <[email protected]> wrote in message news:[email protected]..
>
All,
Any help on this would be appreciated. We have a servlet that calls a native method
and we load the native library in the servlet's 'init()' method so the servlet
gets loaded only once. However, periodically, I get the following error:
java.lang.UnsatisfiedLinkError : Native Library/opt/shared2/weblogic/myserver/servletclasses/twtc/servlet/toc/toclib.so
already loaded in another classloader
It seems to bring down weblogic when this happens.
Why does this happen?
Is there a way around this?
As a test, I called System.load() 10 times outside of the init function with the
same library and it did not fail once but it does periodically in the init() function
of my servlet, which implies that the init function is being called more than
once.