[slf4j-user] Library best practice

[Boris Unckel]

Hi Martin,

Martin Jericho wrote:
> I've been reading the thread in the dev forum about moving the LoggerFactory 
> to the API, and being a SLF4J newbie I would appreciate it if someone could 
> help me with a couple of basic questions.
>
> I have a library in which I would like to use SLF4J for logging.
>
> Q1.  Is the "typical usage pattern" in the user manual valid for library 
> classes?  I would have thought that the user of the library would set the 
> Logger instance via a setter method rather than it being instatiated 
> automatically by the class itself.  I suspect however that library classes 
> are supposed to instantiate their own Loggers, otherwise why were people 
> complaining that the LoggerFactory wasn't in the API?
>   
Two things:
1) Do not use a static a logger, obtain the logger in the class itself.

> Q2.  If library classes are indeed supposed to instantiate their own 
> Loggers, am I right in assuming that there is to be a Logger for each class, 
> rather than one for the library as a whole?  Would it be considered very bad 
> practice if there was only one Logger for the whole library, having the name 
> of the package rather than a single class?
>
>   
2) Use a logger per class, the configuration of the underlying log 
system can be used to configure the
levels and handlers/appenders/filters per package. But you still have 
the flexibility to configure it
per class.

> Q3.  I would still like to know the answer to the question I posed a few 
> hours ago, which is how the classloader knows at runtime that it should use 
> the LoggerFactory from the implementation jar instead of the "dummy" one in 
> the API jar.
Other mail in this thread.

Regards
Boris.