[slf4j-user] Using log4j repositorySelector with slf4j

[George Wilder]

The current implementation(1.7.5) of slf4j's Log4jLoggerFactory caches
log4j Logger instances in a singleton using a map keyed by Logger name.
This caching will prevent the discovery of additional Logger instances that
happen to have the same name, but reside in a different Repository (which
LogManager.getLogger() would have selected if the cache was not used, since
getLogger() uses RepositorySelector first, then looks up the logger by name
from the returned repository.

This behavior causes custom implementations of RepositorySelector in log4j
to appear as if they are not working properly, sending output configured
for one Logger in Repository 2 to a different Logger configured in
Repository 1 when Loggers in both repositories have the same name (like
"org.springframework").

An alternative that appears to solve the problem of caching Loggers only by
name is to calculate the key by name+LogManager.getLoggerRepository().
This has the effect of caching Loggers using both the name and the
Repository, effectivly preventing the problem of missing loggers when using
custom repository selectors.

Has anyone else had this problem/solution?  I saw bug entry #43, but the
solution there focused on logBack, rather than the map key in slf4j's
implementation of Log4jLoggerFactory.
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