Logging formatter in log4j sandbox

[Curt Arnold <ca...@apache.org>]

I'm sure the timing sucks, but since the scuttling of the 1.2.10  
release involves formatting log messages and I have recently been  
doing some things in the log4j sandbox, I thought that I would bring  
that work to your attention.  The project can be checked out from  
http://svn.apache.org/repos/asf/logging/sandbox/log4j/formatter.

One of the problems with adding formatting to the Logger class in  
log4j is that there are several widely used formatting conventions:  
java.text.MessageFormat has been in Java for quite some time,  
java.util.Formatter was just added in JDK 1.5 (similar to C's  
sprintf) and the UGLI/SLF4J effort added a syntax similar but  
distinct to MessageFormat  
(org.apache.log4j.helpers.MessageFormatter).  Currently the log4j  
code uses both java.text.MessageFormat (in the l7dlog methods) and  
o.a.l.helpers.MessageFormatter (in the debug(String fmt, ...) methods.

The sandbox effort intention was to remove formatting from the Logger  
class and to allow the user to pick the formatter of their choice,  
while still being able to bypass argument boxing, array creation and  
formatting on calls below the threshold.  The formatter project adds  
three static classes LogMF, LogSF and LogF which log using the  
java.text.MessageFormat, UGLI/SLF4J formatter and java.util.Formatter  
respectively.  In use the code would look like:

LogMF.debug(logger, "User {0} logged out after {1} seconds",  
username, duration);

The original discussion can be read at http://marc.theaimsgroup.com/? 
l=log4j-dev&m=113704872508753&w=2

I don't know the pattern syntax of the .NET formatter in use.  If it  
is similar to one of the Java formatters, then I would use the  
corresponding class name.  Otherwise, I would choose a slightly  
different name in case we ever wanted to emulate one of the Java  
formatters in .NET (actually, you might already be able to use  
java.text.MessageFormat from J#).

p.s. I had intended to add ResourceBundle variants of the methods  
with signatures like:

static void debug(Logger logger, ResourceBundle bundle, String  
fmtKey, ...);