[slf4j-user] Java 5 version of SLF4J?

[Simon Kitching]

Erik van Oosten schrieb:
> Christopher,
>
> As I wrote already on Feb 17:
> 	There is another aproach, as taken by http://code.google.com/p/log5j/. It is
> 	a wrapper around log4j. I wish they had made it for SLF4J!
>
> I am still waiting for someone to this for SLF4J. It should not be hard. I did not yet find the time myself :(
>   

Sigh. Broken broken broken.

Re the "feature" for determining which category to create a logger for,
see the documentation for Exception.getStackTrace. There is no guarantee
that valid info about the callstack is available. So this code will work
fine under unit testing, then may start emitting messages to the wrong
categories when run in a high-performance environment. That will be fun
to debug...

Re the printf-style formatting:

  log.debug("format str", arg0, arg1, arg2);

is exactly equivalent to:

  push "format str" onto stack
  tmp = new Object[3];
  tmp[0] = arg0;
  tmp[1] = arg1;
  tmp[2] = arg2;
  push tmp onto stack
  invoke log.debug
  (and of course garbage-collect the tmp object later..)

So in practice, for good performance you need
  if (log.isDebugEnabled())
around each call anyway. In which case, the printf-style stuff gives no
performance benefits at all; if something is going to be logged then the
formatting is nowhere near the bottleneck step.

The SLF4J fake-varargs approach, where the api allows 0,1 or 2 params is
slightly better, as it avoids the "new Object[]" call. But for best
performance, isDebugEnabled should be used anyway.

Regards,
Simon