[slf4j-user] Best practice on declaring Loggers

[Simon Kitching]

This page is from the wiki for the apache commons-logging project, but
the same general principles apply to SLF4J too (and is explicitly
discussed):

http://wiki.apache.org/jakarta-commons/Logging/StaticLog

Regards,

Simon

On Wed, 2006-06-14 at 11:17 +1000, whoman at exemail.com.au wrote:
> Gday all,
> This would seem to imply that to log in static methods we should issue a 
> LoggerFactory.getLogger() on every invocation  and thus be able to log into 
> the correct context. Is this accurate, assuming it's not an often used method.
> Cheers,
> Will
> 
> At 06:12 AM 14/06/2006, you wrote:
> 
> 
> >At 12:30 PM 6/13/2006, Konstantinos Karadamoglou wrote:
> >>Hello all,
> >>
> >>Which is the best practice of declaring Loggers? For instance, should 
> >>they be static, private, final? and why?
> >
> >I recommend that loggers members be declared as instance variables instead 
> >of static.
> >
> >Static logger members cost a single variable reference for all instances 
> >of the class whereas an instance logger member will cost a variable 
> >reference for every instance of the class. For simple classes instantiated 
> >thousands of times there might be a noticeable difference.
> >
> >However, more recent logging systems, e.g log4j or logback, support a 
> >distinct logger context for each application running in the application 
> >server. Thus, even if a single copy of log4j.jar or logback-classic.jar is 
> >deployed in the server, the logging system will be able to differentiate 
> >between applications and offer a distinct logging environment for each 
> >application.
> >
> >More specifically, each time a logger is retrieved by invoking 
> >LoggerFactory.getLogger() method, the underlying logging system will 
> >return an instance appropriate for the current application. Please note 
> >that within the same application retrieving a logger by a given name will 
> >always return the same logger.
> >
> >If the logger is static, then it will only be retrieved once when the 
> >hosting class is loaded into memory. If the hosting class is used in only 
> >in one application, there is not much to be concerned about. However, if 
> >the hosting class is shared between several applications, then all 
> >instances of the shared class will log into the context of the application 
> >which happened to fist load the shared class into memory.
> >
> >In summary, except for classes with few members and instantiated very 
> >frequently, logger members should be instance variables.
> >
> >I hope this helps,
> >
> >--
> >Ceki Gülcü
> >http://ceki.blogspot.com/
> >
> >_______________________________________________
> >user mailing list
> >user at slf4j.org
> >http://slf4j.org/mailman/listinfo/user
> >
> 
> 
> 
> _______________________________________________
> user mailing list
> user at slf4j.org
> http://slf4j.org/mailman/listinfo/user