[logback-user] Compiler selecting wrong Logger method

[Chris Pratt]

Sure, it uses an extension of the java.text.MessageFormat syntax that
allows for unlimited formatted varargs, and allows using dot-notation to
prevent evaluation of the methods until it's been deemed necessary.  With
the current libraries (all of them really), you have to evaluate all the
javabeans that hold the data you are looking to log before it's decided
whether to log the information or not.  In other words:

log.debug("Loading Student [" + sdnt.getNumber() + "] " + sdnt.getName() + "
Enrolled: " + new SimpleDateFormat("yyyy-MM-dd").format(sdnt.
getEnrollmentDate()));

Means that a lot of work is done and discarded when the debug level on this
file is set to info or less.  SLF4j is a little better, but not much:

log.debug("Loading Student [{}] {} Enrolled: {}",new Object[] {sdnt.
getNumber(),sdnt.getName(),new SimpleDateFormat("yyyy-MM-dd").format(sdnt.
getEnrollmentDate())});

Yes, of course you could (and probably should) wrap each and every call to
the log system in if(log.isDebugEnabled()) {}.  But we all know that is
ugly and easy for Jr programmers to forget.  My library puts off the
evaluation until after it's been decided that the information is necessary,
then efficiently outputs the message, like this:

log.debug("Loading Student [{0.number}] {0.name} Enrolled:
{0.enrollmentDate,date,yyyy-MM-dd}",student);

No muss, no fuss and the TextFormat utility is completely usable standalone
(as well as the advanced dot-notation utilities).
  (*Chris*)

2012/2/13 Thorbjørn Ravn Andersen <thunderaxiom at hotmail.com>

> Could you summarize your solution briefly here for the completeness of the
> archives?****
>
> ** **
>
> (Personally I’d just be happy with a resolution so I can easily have more
> than two {}-arguments)****
>
> ** **
>
> /Thorbjørn****
>
> ** **
>
> *From:* logback-user-bounces at qos.ch [mailto:logback-user-bounces at qos.ch] *On
> Behalf Of *Chris Pratt
> *Sent:* 9. februar 2012 17:16
>
> *To:* logback users list
> *Subject:* Re: [logback-user] Compiler selecting wrong Logger method****
>
> ** **
>
> Well, I'd be happy to throw my solution in as an option.  You, and Ceki,
> can find more information at http://code.google.com/p/anodyzed There's
> information in the wiki documents and more on the way when I get a chance.
> If there's any information you think is missing, please don't hesitate to
> let me know and I'll do what I can to remedy the situation.  Thanks.
>   (*Chris *)****
>
> On Feb 9, 2012 1:00 AM, "Thorbjørn Ravn Andersen" <
> thunderaxiom at hotmail.com> wrote:****
>
> Ceki has not yet decided on the proper way to do varargs in slf4j.  Until
> then, no official API.
>
> See http://bugzilla.slf4j.org/show_bug.cgi?id=31 for the full history.
>
> /Thorbjørn
>
> -----Original Message-----
> From: logback-user-bounces at qos.ch [mailto:logback-user-bounces at qos.ch] On
> Behalf Of Stein, Eric
> Sent: 6. februar 2012 14:24
> To: logback users list
> Subject: Re: [logback-user] Compiler selecting wrong Logger method
>
> <sigh/> I'm a nitwit. I got confused because at my last job we used a
> wrapper around slf4j, and the signature of the method was debug(String,
> Object...). Out of curiosity, is there a reason why that format wasn't
> used?
> The compiler should be smart enough to call the more specific debug(String,
> Object, Object) when appropriate. Changing from Object[] to Object...
> should
> also be backwards-compatible...
>
> Thanks, Marco!
>
> Eric
>
> -----Original Message-----
> From: logback-user-bounces at qos.ch [mailto:logback-user-bounces at qos.ch]
> On Behalf Of BRESCIANI, MARCO (MARCO)
> Sent: Monday, February 06, 2012 8:12 AM
> To: logback users list
> Subject: Re: [logback-user] Compiler selecting wrong Logger method
>
> If I'm not wrong, using - Object[] - or the variable list - Object... - is
> a
> bit different and in order to have the correct method, you should write
> this:
>
>        LOGGER.debug("Hi {} {} {}", new Object[] { arg1, arg2, arg3 });
>
>
>
> MARCO BRESCIANI
> ALCATEL-LUCENT
> SENIOR SW CRAFT TERMINAL DEVELOPMENT ENG NETWORKS - IP DIVISION WT PRODUCT
> UNIT via Trento, 30 - 20059 Vimercate (MB) - Italy
> Phone: +39 039 686 6279
> Fax: +39 039 686 5600
> Marco.Bresciani at alcatel-lucent.com
>
> -----Original Message-----
> From: logback-user-bounces at qos.ch [mailto:logback-user-bounces at qos.ch]
> On Behalf Of Stein, Eric
> Sent: Monday, February 06, 2012 1:59 PM
> To: logback-user at qos.ch
> Subject: [logback-user] Compiler selecting wrong Logger method
>
> I'm seeing a funny error when trying to write to logback.
>        import org.slf4j.Logger;
>        import org.slf4j.LoggerFactory;
>
>        final String arg1 = "arg1";
>        final String arg2 = "arg2";
>        final String arg3 = "arg3";
>        LOGGER.debug("Hi {} {}", arg1, arg2);
>        LOGGER.debug("Hi {} {} {}", new String[] { arg1, arg2, arg3 });
>        LOGGER.debug("Hi {} {} {}", arg1, arg2, arg3);
>
> The last line is giving this error message:
>
> The method debug(Marker, String, Object, Object) in the type Logger is not
> applicable for the arguments (String, String, String, String)
>
> I don't see why it isn't using the method whose signature is debug(String,
> Object[]), especially given that I'm not using a Marker.
> I'm running in Eclipse Indigo, and my classpath looks like this:
>
> logback-classic-1.0.0.jar
> logback-core-1.0.0.jar
> slf4j-api-1.6.4.jar
>
> Does anybody know why the compiler is using the wrong method?
>
> Thanks,
> Eric Stein
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