Should I put log4j.properties file into library?

Question

I have a library project. This project uses log4j for logging.

Should I put log4j.properties into generated jar?
If it is not a good practice, could you tell me why?

Answer 1

You should put your log4j.properties outside your jar file because it will be easier to modify it. If the application does not force a reload of the configuration (you can do that) then a simple restart will load the config (while modifying it inside a jar file means usually a rebuild). If the application does know how to reload it, then your changes will be almost instantly applied. This is very important when you have application in production environment, and you want to change a logging setting (like the log level) in order to get more info but not to stop the application for this (or worse, rebuild it).

Answer 2

No, I would not include log4j.properties in your src/main/resources if it's just a library - people will use your library, and people will have to configure how it should log.

But there is another problem: if you put it in your jar, others will have the log4j in their classpath too. So, if they want to have a custom configuration for log4j (which they will do), the ClassLoader will pick the first file it can find.

Also, if you have a library, I would suggest to use slf4j instead, so your users can choose their favourite logging framework.

For testing purpouses, it's okay to include log4j in src/test/resources.