Log4J

Debug and Trace in log4j to set here: log4jproperties
It usually can be found in package/conf or some simillar path.
then you set the log4j property as follow:
log4j.logger.net.mycompany=TRACE,mycompany_package_log

Java Wrapper Service

Java wrapper service is a java package that allow you to install and run your java programs as services in windows. When looking at logs generated log4j, you will get some of the followings:
INFO   | jvm 1    | 2011/02/02 10:57:08 | WrapperManager Debug: Send a packet PING : ping
DEBUG  | wrapperp | 2011/02/02 10:57:08 | read a packet PING : ping
DEBUG  | wrapperp | 2011/02/02 10:57:17 | send a packet PING : ping
INFO   | jvm 1    | 2011/02/02 10:57:17 | WrapperManager Debug: Received a packet PING : ping
Apparently this shows that the service is trying to see if there is a live JVM or not, and if not it will uses its own (I guess).