https://issues.apache.org/bugzilla/show_bug.cgi?id=57172
--- Comment #2 from Joern Huxhorn <jhuxh...@googlemail.com> ---
How about indicating that the web application is trying to use the web
application class loader after it has been stopped instead of throwing a
non-descriptive NPE?
The webapp in question was simply using a Java 8 forkjoin.
at
java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
at java.util.HashMap$KeySpliterator.forEachRemaining(HashMap.java:1540)
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:512)
at
java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:502)
at java.util.stream.ReduceOps$ReduceTask.doLeaf(ReduceOps.java:747)
at java.util.stream.ReduceOps$ReduceTask.doLeaf(ReduceOps.java:721)
at java.util.stream.AbstractTask.compute(AbstractTask.java:316)
at java.util.concurrent.CountedCompleter.exec(CountedCompleter.java:731)
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
at
java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:902)
at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1689)
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1644)
at
java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)
Are you seriously suggesting that leaving the current behavior is preferable
to, say, a proper error message?
Beside that: the webapp behaved like that without being stopped. This is
related to undeploy magic performed by Tomcat regarding ThreadLocal and this
problem shows up after RE-deploying an application without restarting Tomcat.
As I mentioned in my original report: if you search for this on the web then
you'll find mentions of similar problems from 2006. I can't be sure since they
just refer to generic NPE's in the findResources method spread over various
Tomcat versions.
If you consider the usage of a ThreadLocal a memory leak in our app then, yes,
we have a memory leak. I, on the other hand, would argue that it's the
responsibility of the application server to shield web-applications from leaks
like that by using separate worker threads for each webapp.
I'm fully aware how this is supposed to work. But it isn't. I just observed
this NPE in a live web application.
Alright. Let's settle for a compromise. Just add
if(resources == null) {
throw new IllegalStateException("OMG! SNAFU! This can't happen!
findResources has been called on a (probably) stopped web context! /o\\");
}
This would be easier to search for than a simple NPE and would probably prove
my point in the future.
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