samskivert to use logging services without creating a dependency on a logging
implementation.
This is basically what JCL (Jakarta Commons Logging) does except they do
auto-detection based on what's in the classpath and we're only going to
auto-detect log4j and only use it if we see that a log4j configuration has been
provided via a system property (or maybe not at all, I'm not sure yet). The
point is avoid the major gripe about JCL which is that when you stick some
logging system's jar file into your classpath for some other dependency (or
it's there for unknown reasons like maybe your servlet container uses it), all
of a sudden your log output disappears or breaks.
I had an idea while doing this and couldn't resist slipping it in: all of the
logging methods take varargs additional parameters which are a set of key/value
pairs to append to the log message in our standard format with an optional
final exception to be logged as well.
So instead of:
log.warning("Oh crap, the fibbleminscher has exploded [state=" + 15 +
", monkeys=" + StringUtil.toString(_monkeys) + "].");
You do:
log.warning("Oh crap, the fibbleminscher has exploded.", "state", 15,
"monkeys", _monkeys);
The formatter automatically does the StringUtil.toString magic on the arguments
(and does it safely so that if toString throws an exception the log message
isn't lost). You can also throw an exception in the mix:
log.warning("Oh crap, the fibbleminscher has exploded.", "state", 15,
"monkeys", _monkeys, ioe);
Or supply one with no parameters:
log.warning("Oh mammy!", ioe);
Or even just log an exception if you have nothing pithy to add:
log.warning(ioe);
Some research shows that other people have started doing this in their logging
systems as well under the fancier name of parameterized logging. The big
benefit is that you can pass objects that are expensive to toString() and avoid
toString()ing them unless you're actually going to generate the log message.
In our case we also get the benefit of our standard formatting and less
cluttered code (begone lots of + ", ...=" + typing).
I'm going to be doing away with the old samskivert Log code and converting all
of our libraries (and projects) to use this new shim so that we can easily
switch to using log4j, which for other reasons we want to use instead of Java's
built-in logging.
git-svn-id: https://samskivert.googlecode.com/svn/trunk@2311 6335cc39-0255-0410-8fd6-9bcaacd3b74c
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