Hello,
I have a question using native JNI shared objects within a servlet running
under Tomcat 5.5. Our servlet code depends on some shared .dll files (for
windows, and .so files for Linux). so we have classes that have code such as:
public class Abc {
public native static boolean nativeF0(int a,String b);
/* ... other native method declarations ... */
static {
System.loadLibrary("objectfile");
}
}
Obviously the idea is that the shared object objectfile.dll is loaded whenever
the native methods are accessed. However, Tomcat seems to create a new Java
class-loader whenever a web-app is reloaded via using the Tomcat "manager"
web-app. Because of the new class-loader, the "static {
System.loadLibrary(...); }" method is re-executed and the 2nd call to
loadLIbrary yields an JRE error "java.lang.UnsatisfiedLinkError: Native Library
objectfile.dll already loaded in another classloader" followed by a JRE crash.
The workaround is to completely stop and restart the entire Tomcat server every
time I modify my web-app. But this is cumbersome and makes our web-app harder
to deploy and patch. Catching and ignoring the UnsatisfiedLinkError solves
nothing because the classes loaded in the 2nd class-loader can't find the
native methods.
Can someone please give me some advice as to how to do one of the following:
a. Unload my original objectfile.dll when my web-app is stopped so when it
is restarted it loads normally in the new class-loader
b. Connect the native libraries from the first class-loader to the second
class-loader after the web-app is reloaded
c. Other possibilities to work around this?
Thank you,
Eric Johanson
