SolrJ Classloader Leak Demonstration

Demo project for this Question on Stackoverflow: http://stackoverflow.com/q/39741147/4864870

The Classloader leak is reproducible under the following conditions (at least this is the environment which I have tested):

• Tomcat Version: Apache Tomcat/8.0.14 (Debian)
• JVM Version: 1.8.0_91-b14
• JVM Vendor: Oracle Corporation
• OS Name: Linux
• OS Version: 3.16.0-4-amd64
• Architecture: amd64

Note: This project already contains a "ClassLoader-Leak-Preventor" (de.test.SSLClassloaderLeakPreventor). So if you just run this project you will not see the classloader leak!

You have to disable the Shutdown-Hook in de.test.SSLClassloaderLeakPreventor if you want to reproduce the leak.

Environment

1. Solr
   The URL defined in SolrJConfig.SOLR_URL points to the Solr server.
   • download: http://www.apache.org/dyn/closer.lua/lucene/solr/6.2.1
   • run: solr start -p 8984
2. Certificate with unparseable extension
   I don't know exactly where the certificate with the unparseable extension came from. I haven't installed any additional certificate in the keystore. The cacerts Keystore used in my tests is attached.

Potential for improvement

1. The SSLClassloaderLeakPreventor simply removes the Exception. Maybe it would be saver to check if there are references to Classes from the WebappClassLoader
2. Integration in classloader-leak-prevention, see mjiderhamn/classloader-leak-prevention#58