Log4j : How to name the logfile dynamically

[Mishra Anshu]

Hi,
I want to have the name of my log file to be decided at run time.
Like, suppose a command line argument is to be included in the log file name.
How to do it, declaratively..i.e. using log4j.properties file or log4j.xml file ?

This is how it can be done, programmatically :-

RollingFileAppender logAppFile = new RollingFileAppender(new PatternLayout(Pattern),"urlogfileName"+arg[0], true);
 
logAppFile.setThreshold(Level.ALL);
logAppFile.setMaxBackupIndex(20);
logAppFile.setMaxFileSize("5000KB");
 

It has to be rolled.
I feel it is quite a common requirement, whenever you want to run your program everyday, for different args passed to it.

[Carol Enderlin]

Use system property on the command line

-Dfoo=bar

Then in the properties or xml config file grab the value of foo with ${foo}

[Mishra Anshu]

Thanks Carol !

I think, since I decide the name of the logfile depending upon what is passed as args, I would use :-

System.setProperty("foo","whatEverName"+args[0]);

Thanks
[ October 19, 2006: Message edited by: Mishra Anshu ]

[Carol Enderlin]

I'd recommend using "-Dlog4j.debug" on the command line when you're working on setting that up so you can see how log4j is getting configured. If you're programmatically setting the system property you'll need to make sure the system property is set before log4j tries to use it, especially if you've got log4j.properties or log4j.xml in the classpath.