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Because God knows, Java needs another logging framework. Seriously does ANYONE get any additional value out of the morass of crappy logging systems out there over and above System.out.println? Log4J is PARTICULARLY brain-damaged, with its refrain of "ooh, someone put a log4j.xml in their JAR (one of hundreds), that beats your log4j.properties.". Or SL4Js amazing performance of "1.6 doesn't work with Scala because of…
Never had a problem with slf4j on top of log4j. By the way, I use DEBUG in development and INFO in production. The ratio of logging messages between the two levels is about 1 for 50. Definitely an useful feature on top of System.out.println. I also change log levels for certain packages because some libraries are too verbose. Why are you so bitter ?
I am currently in what you could consider log hell with a product based on OSGi. We have been using ops4j logging which has done a fantastic job of adapting the prevalent logging frameworks (log4j, slf4j, logback, and JUL) into the SLF4J API and we don't even have to think about it anymore.