Joel, On 8/2/18 12:10 AM, Joel Hirsh wrote: > Thanks for the explanation. I will look towards the tomcat mailing list. > > Per your request about the entire stack trace - there is more above the > first call to PDFBox, but the root cause in both cases is indeed > "java.lang.NoClassDefFoundError: > Could not initialize class". > And I have seen that same error with other ClassLoader problems under > Tomcat.
I understand, but there is a root-cause for "Could not initialize class". Usually, it's something that fails unexpectedly in a static initializer or something like that, and it should have its own separate stack trace. -chris > On Wed, Aug 1, 2018 at 1:39 PM, Christopher Schultz < > [email protected]> wrote: > >> Joel, >> >> On 8/1/18 3:54 PM, Joel Hirsh wrote: >>> However, your comment that "Tomcat doesn't unload libraries" is not >>> entirely true. There is an explanation of such symptions at >>> https://haraldk.github.io/TwelveMonkeys/, under the section "Deploying >> the >>> plugins in a web app". >> >> Thanks for posting that. Lemmie 'splain. >> >> In a servlet container, web applications (aka "contexts") each have >> their own ClassLoader and if the application is undeployed or >> re-deployed, then that ClassLoader will be freed for GC. If a class >> loaded by that webapp's ClassLoader is still in use, you have a memory >> leak situation knows as a "pinned ClassLoader". >> >> It happens all the time when you use a system-global cache such as >> ImageIO does. This can happen with JDBC DriverManger and a handful of >> other common APIs and it can be a serious problem for servers where >> there are lots of redeployments. You can also start to see errors like >> "ClassCastException: Cannot cast foo.bar.Class to foo.bar.Class" because >> instanceof-ness is defined not just by Class but also by ClassLoader. >> >> The IIOProviderContextListener mentioned in that documentation is one >> strategy to handle the unfortunate way ImageIO caches classes. Another >> strategy is to put the library into a place where it is accessible to >> all web applications instead of just one. >> >>> Just putting jars in a shared folder did not help. >> >> Here is where asking on the Tomcat mailing list *will* be a good idea. >> Make sure to give your exact Tomcat version and explain where you put >> the library. >> >> Can you post the *entire* stack trace from the failure? It looks like >> it's incomplete -- it doesn't seem to have a "true root cause". It just >> says "Could not initialize class" because "Could not initialize class". >> Somewhere there should be a real root cause like NullPointerException or >> something that can actually be debugged. Def post that to the Tomcat >> mailing list as well if you post. >> >> -chris >> >> >
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