How to avoid Classloader Leak with JPA, Hibernate and Spring on Tomcat

Question

The Open J2EE Web Template is a showcase application for wicket - JPA with Spring and Hibernate that runs on a Tomcat7 servlet container. Its Maven build script appears to u

Answer 1

I have seen this same webapp memory leak on Tomcat7 + OpenJPA2.4.1 + ValidationAPI1.x + hibernate-validator-5.2.1 + jboss-logging.jar

Problem is indeed jboss-logging.jar creates a subclass of java.util.logging.Level instances. May not be a problem if jar is provided by J2EE container but will happen with mywebapp/WEB-INF/lib distribution. I have created a fork of package to disable subclassing. Problems went away and webapp hot redeployments work fine.

Heapdump of GC root path indicates a source of problem, JDKLevel subclass keeps a webapp in memory and soon JVM run out of PermGen memory.

this     - value: org.apache.catalina.loader.WebappClassLoader #2
 <-      - class: org.jboss.logging.JDKLevel, value: org.apache.catalina.loader.WebappClassLoader #2
  <-      - class: org.jboss.logging.JDKLevel, value: org.jboss.logging.JDKLevel class JDKLevel
   <- levelObject     - class: java.util.logging.Level$KnownLevel, value: org.jboss.logging.JDKLevel #6
    <- [1]     - class: java.lang.Object[], value: java.util.logging.Level$KnownLevel #12
     <- elementData     - class: java.util.ArrayList, value: java.lang.Object[] #5160 (10 items)
      <- value     - class: java.util.HashMap$Entry, value: java.util.ArrayList #3532
       <- [0]     - class: java.util.HashMap$Entry[], value: java.util.HashMap$Entry #21639
        <- table     - class: java.util.HashMap, value: java.util.HashMap$Entry[] #280 (16 items)
         <- intToLevels (sticky class)     - class: java.util.logging.Level$KnownLevel, value: java.util.HashMap #375

edit Created JBoss Jira ticket for this bug (https://issues.jboss.org/browse/JBLOGGING-118)