package  org.apache.log4j.net;

 public   class  JMSAppender  extends  AppenderSkeleton {
...
TopicSession topicSession;
....
  /**
     This method called by {@link AppenderSkeleton#doAppend} method to
     do most of the real appending work.  */
   public   void  append(LoggingEvent event) {
     if (!checkEntryConditions()) {
       return ;
    }

     try  {
      ObjectMessage msg = topicSession.createObjectMessage();
       if (locationInfo) {
	event.getLocationInformation();
      }
      msg.setObject(event);
      topicPublisher.publish(msg);
    }  catch (Exception e) {
      errorHandler.error("Could not publish message in JMSAppender ["+name+"].", e,
			 ErrorCode.GENERIC_FAILURE);
    }
  }
...
}

 package  org.apache.log4j.net;

 public   class  IAOMJmsAppender  extends  JMSAppender {
...
     public   void  append( LoggingEvent event ) {
         if  ( !checkEntryConditions() ) {
             return ;
        }

         try  {
            ObjectMessage msg = topicSession.createObjectMessage(); // тут падает
       ....
    }

...
}