I have just started using Google Guice with my Tomcat webapp, and have noticed the following in the catalina.out file whenever the WAR file is undeployed:
May 16, 2011 5:37:24 PM org.apache.catalina.startup.HostConfig checkResources
INFO: Undeploying context [/app]
May 16, 2011 5:37:24 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads SEVERE: A web application appears to have started a thread named [com.google.inject.internal.util.$Finalizer] but has failed to stop it. This is very likely to create a memory leak.
May 16, 2011 5:37:24 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap SEVERE: A web application created a ThreadLocal with key of type [null] (value [com.google.inject.internal.InjectorImpl$1@10ace8d]) and a value of type [java.lang.Object[]] (value [[Ljava.lang.Object;@7e9bed]) but failed to remove it when the web application was stopped. To prevent a memory leak, the ThreadLocal has been forcibly removed.
Does anyone know what causes this, or how I can stop it from happening?
I have only followed the instructions from here http://code.google.com/docreader/#p=google-guice&s=google-guice&t=ServletModule
... and haven't done anything fancy with it yet. I just have 2 servlets and a filter.
Thanks!
If you are getting this when you shutdown the webapp, I wouldn't worry too much. This type of resource leak on app. shutdown is common. They do become a problem when you frequently do hot deploys (i.e. un-deploy many times without killing the JVM), but they won't be problematic when a cold deploy is done (un-deploy/deploy is done while killing the JVM before re-deploy).
A common tactic is that you do hot-deploys during development (as they are typically faster than cold-deploys), and only do a cold deploy when the resource leak starts to affect your performance. Then, in production you do a cold deploy on every deploy. Given the number of code/libraries that has this type of leak, trying to eliminate them would be hard IMO.
According to the Guice issue 630 it should be fixed in the next Guice version (as of 11/2011), i.e. when the Guava dependency is upgraded to r10+.
It seems that the fix is still not in, according to Guice issue 288.
This helped me to get rid of "SEVERE" log entry for com.google.inject.internal.InjectorImpl:
injector = null;
System.gc();
Where injector was the result of Guice.createInjector(...modules...)
I admit, it looks like I didn't read about bad habit of calling System.gc(), but it totally makes sense, since Guice uses weak references internally.
P.S. Tomcat 8, Java 8, Guice 3.0
来源：https://stackoverflow.com/questions/6025089/guice-tomcat-potential-memory-leak