log4j - DailyRollingFileAppender, override subAppend() - log4j

Question

I am new to log4j's DailyRollingFileAppender class and I would like to use this to perform daily rotation of the log file and at the same time would like to also manually modify the log file every time there is an event triggered to log event.
For example, I would like to always increment the value by one for "TOTAL COUNT:" inside the log file. How can I go about doing that?
Example of the log content:
07 Oct 2011 16:57:51 [INFO ] - Failed
07 Oct 2011 16:57:51 [WARN ] - Failed
07 Oct 2011 16:57:51 [ERROR] - Successful
07 Oct 2011 16:57:51 [FATAL] - Failed
07 Oct 2011 16:57:52 [DEBUG] - Successful
07 Oct 2011 16:57:52 [INFO ] - Failed
07 Oct 2011 16:57:52 [WARN ] - Failed
07 Oct 2011 16:57:52 [ERROR] - Successful
07 Oct 2011 16:57:52 [FATAL] - Failed
07 Oct 2011 16:57:53 [DEBUG] - Successful
07 Oct 2011 16:57:53 [INFO ] - Failed
07 Oct 2011 16:57:53 [WARN ] - Failed
07 Oct 2011 16:57:53 [ERROR] - Successful
07 Oct 2011 16:57:53 [FATAL] - Failed
07 Oct 2011 16:57:54 [DEBUG] – Successful
TOTAL COUNT: 15

Answer 1

It seems overriding subAppend() in the DailyRollingFileAppender is the way to go. You'll also have to be cautious when calling super.subAppend(), as the WriterAppender implements it like this:
protected void subAppend(LoggingEvent event) {
this.qw.write(this.layout.format(event));
// ...
}
and you don't want layout with your "TOTAL COUNT" line.
In my subAppend() I'd copy exactly what D.R.F.Appender does, adding:
line counting logic, if not present elsewhere,
a condition checking if a special line should be printed, then formatting and printing it directly to qw.