I'm not sure I understand the question. But if you want to have RHQ scan your log4j log files, looking for certain log messages, it can do that. On matching log entries it will generate an Event in RHQ, which can be inspected, trigger an alert, etc.
If you are wondering whether you can send alerts directly into RHQ, there is no direct mechanism for that. Although using the above approach you can do it by writing to a file that is being scanned, and therefore generate Events. There may be other ways as well.