#970 single logging framework should be enforced

[jjjimenez100]

Replaces all usages of log4j with the Slf4j API. This PR also removes references of log4j in pom and resource files.

[iluwatar]

@jjjimenez100 please resolve the conflict

[jjjimenez100]

Fixed by bf2b3cb Although I'm not really sure that was the best way to fix the conflict since I did it on Ghub's UI. 😅

[iluwatar]

The changes look good, but log4j is still present in several places. You can try to grep the codebase like grep -r -l "log4j" to see where it is still referenced.

[jjjimenez100]

The changes look good, but log4j is still present in several places. You can try to grep the codebase like grep -r -l "log4j" to see where it is still referenced.

Ah right. About that, I think the only remaining are the ones under the naked-objects pattern. However, it seems like Apache ISIS' withLoggingAt(..); only accepts the concrete class of log4j's Level. Should I simply just remove that line?

[iluwatar]

It's ok for me to remove those statements. It would be also good to scan for System.out.println style logging. I think I've seen some of those in the codebase.
There are some conflicts now that should be resolved.

[jjjimenez100]

The only remnants of System.out... now would be on:

• The Composite pattern
• ConsoleLoggerModule

since the examples has test cases asserting the output from the console (which I believe the way the example was structured to begin with)

For the log4j ones, stuffs remaining are on persistor.properties and all of them are already commented.

Let me know if there are any other changes I should do. 😄

[iluwatar]

Thanks @jjjimenez100 for the hard work you've done