JDBC Driver has been forcibly unregistered by Tomcat 6

问题

I am getting this error about mysql:

INFO: Shutting down log4j   
09-ene-2014 9:57:21 org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc
GRAVE: A web application registered the JBDC driver [com.mysql.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
09-ene-2014 9:57:21 org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
GRAVE: A web application appears to have started a thread named [Abandoned connection cleanup thread] but has failed to stop it. This is very likely to create a memory leak.

There're a lot information about it in others questions. I already updated my mysql lib to the version 5.1.28 (before, I was working with 5.0.8 which contains a bug about it) but it doesn't still work. I have checked that I have that lib in my war. Like a test, I deleted my mysql lib from WEB-INF/lib and I copied to TOMCAT/lib and I missed that error, why?. I don't want to copy that jar in TOMCAT/lib. I'm working with Tomcat6.

来源：https://stackoverflow.com/questions/21015991/jdbc-driver-has-been-forcibly-unregistered-by-tomcat-6