I've reworked the previous formatter sandbox project and have split
it up into two very similar sandbox projects: LogMF and LogSF. Both
simplify efficient parameterized logging by providing a utility class
(o.a.l.LogMF and o.a.l.LogSF respectively) to coordinate formatting
and attempt to defer boxing of primitive types, array creation and
message formatting until after isEnableFor(Level) has been checked.
LogMF supports java.text.MessageFormat pattern syntax and LogSF
supports log4j 1.3 or SLF4J pattern syntax. I've killed LogF (which
used JDK 1.5's sprintf type formatter) for the time being. The
utility classes have been tested against both log4j 1.2.8 and 1.2.14.
The following changes were made from the previous API:
LogF was removed
The classes were moved from org.apache.log4j.formatter to
org.apache.log4j.
LogXF.log and LogXF.logrb were added (where LogXF is either LogMF or
LogSF).
LogXF.error and .fatal were removed (use LogXF.log(logger,
Level.ERROR,...) in its place).
For a log4j 1.3 parameterized log request like:
logger.info("Hello, {}", username);
The equivalents are:
LogSF.info(logger, "Hello, {}", username);
LogMF.info(logger, "Hello, {0}", username);
All single substitution parameter methods have support for all
primitive types. Multiple substitution parameter methods require
Objects. All levels also have an Object[] method. You should not
notice that you do not have vararg capability until after you have
more than 4 arguments.
//
// all the following are legal
//
LogMF.info(logger, "Iteration {0}", 16);
LogMF.info(logger, "Iteration {0}: Tolerance {1}", Integer.valueOf
(i), Double.valueOf(tol));
LogMF.info(logger, "Iteration {0}: Errors {1}", Integer.valueOf(i),
new double[] { Math.PI, Math.PI});
LogMF.info(logger, "Iteration {0}: Tolerance {1}", new Object[]
{ Integer.valueOf(i), Double.valueOf(tol));
//
// Object cast is needed to treat first as a single parameter.
Would result in "Errors: { 3.14, 3.14 }"
//
LogMF.info(logger, "Errors {0}", (Object) new Object[]
{ Double.valueOf(Math.PI), Double.valueOf(Math.PI}));
//
// Without cast array is two substitution parameters, only one of
which is used. Would result in "Errors: 3.14"
//
LogMF.info(logger, "Errors {0}", (Object) new Object[]
{ Double.valueOf(Math.PI), Double.valueOf(Math.PI}));
The logrb methods take the name of a resource bundle and key and load
the resource bundle for the current locale.
LogMF.logrb(logger, Level.INFO, "com.example.widget.LogPattern",
"Greeting", username);
LogSF is provided to support migration of code that used log4j 1.3
style parameterized logging. The simple formatter used did and
does not support arbitrary ordering of replacement which makes it
unsuitable when localization may need to change word order. LogMF
should be used for new code since java.util.MessageFormat supports a
much richer pattern syntax and is well suited for localization.
Earlier performance tests showed no noticeable performance
degradation for using LogSF or LogMF over direct Logger calls using a
current JVM. Your mileage may depend on your VM.
You will get null pointer exceptions if logger or level arguments are
null. The classes should be robust in face on any other parameter
being null.
I believe they are ready for use and do not anticipate any
significant changes in the near future, so feel free to play and give
feedback.
LogMF: svn co https://svn.apache.org/repos/asf/logging/sandbox/log4j/
formatter
LogSF: svn co https://svn.apache.org/repos/asf/logging/sandbox/log4j/
logsf
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