[slf4j-user] Bridging the "other way"

[Steve Cohen]

On http://www.slf4j.org/legacy.html, it says:

Often, some of the components you depend on rely on a logging API other 
than SLF4J. You may also assume that these components will not switch to 
SLF4J in the immediate future.

I have the opposite problem.  I have a suite of applications which 
happily use log4j, but which depend on third party applications, some of 
which use SLF4J.  I want to see their log output, but it is not visible.

What (aside from converting the whole thing to SLF4J, which is a bigger 
deal than you might imagine because the existing application uses a 
home-grown adaptor for log4j) would be my simplest route to making the 
3rd party SLF4J output visible in the application's log4j logs?