Overview of log4j configuration

Question

I am rather confused by how to configure Log4j I have picked up following snippets, but something written that pulls these concepts together would be useful.

• Log4j looks for properties/xml files in the CLASSPATH
• You can supply your own file using PropertyConfigurator.configure(filename) - what if you call this twice. Are the files effectively merged or is only the last one used.
• You can supply an explicit file using -D on the command line

I want to be able to

• Supply a basic config file that remains static
• Allow an individual developer to add an additional file with extra options without having ot exit this main file.

Answer 1

According to this documentation

The existing configuration is not cleared nor reset.

log4j itself stops at the first log4j.properties it find.

So when you call configure, my guess is:

• if some configuration is already done then the current will be merged.
• if configuration has not been done then log4j will not attempt to read any other log4j.properties

Your best best is to probably call configure with global and then with developer-specific file. But this should be easy to test.