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From Curt Arnold <carn...@apache.org>
Subject Re: Varargs support to the sandbox
Date Mon, 11 Feb 2008 08:19:19 GMT

On Feb 10, 2008, at 8:35 PM, Katherine Hale wrote:

> Curt -
>
> Thanks for the fly-by-night introduction. This is what I was  
> thinking in more detail. Again I know this is Java 5, so this would  
> be for Log4J 2.0, although perhaps something comparable could be  
> devised for the current Log4J. I'll just use debug as an example.
>
> I find myself frequently logging like this...
>
> Logger.debug(String.format("First object '%s', second object '%s'",  
> first, second));
>
> When I wish I could just be logging like this..
>
> Logger.debug("First object '%s', second object '%s'", first, second);
>
> The new signature I feel is missing would be something like this...
>
> public static debug(String message, String ... arguments)
>
> After briefly looking at LogMF, this might be doing the same thing.  
> I'm not familiar with MessageFormat, so I don't know if the usage  
> for the "pattern" argument is the same or different from  
> String.format() in Java 5.
>
> 352 /***
> 353 * Log a parameterized message at debug level.
> 354 * @param logger logger, may not be null.
> 355 * @param pattern pattern, may be null.
> 356 * @param arguments an array of arguments to be formatted and  
> substituted.
> 357 */
> 358 public static void debug(final Logger logger, final String  
> pattern,
> 359 final Object[] arguments) {
> 360 if (logger.isDebugEnabled()) {
> 361 forcedLog(logger, Level.DEBUG, format(pattern, arguments));
> 362 }
> 363 }
>
>
> Thoughts?
>

String.format() is an indirect call to the java.util.Formatter class  
that was introduced in JDK 1.5.  The LogF class that was started at  
the same time as LogMF and LogSF but not driven through to release  
used java.util.Formatter.  It is still in the SVN history and could be  
brought forward, but LogSF and LogMF were more immediately useful.   
LogSF was provided as a migration path for the log4j 1.3 message  
formatter which had a syntax similar to, but incompatible with with  
java.text.MessageFormat.  There is no reason to use LogSF in new code.

Your logging statement could look like:

LogMF.debug(logger, "First object '{0}', second object '{1}'", first,  
second);

or

LogF.debug(logger, "First object '%s', second object '%s'", first,  
second);

Since there are two distinct formatters provided in the JDK, it would  
be undesirable for log4j to pick one over the other (or worse yet to  
introduce yet another pattern syntax).

LogMF avoids the construction of the Object[] array until the  
threshold is evaluated which a varargs approach would not do unless  
the JVM was able to detect the array was not going to be used.

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