[slf4j-user] Class path contains multiple SLF4J bindings: gossip and slf4j-log4j12

[Nils Breunese]

Robert Elliot wrote:

Thanks for the fast response!

> Gossip and log4J are both logging systems.

I found that it is a 'plugin for SLF4J', but I didn't know that it was a logging system in its own right.

> The big question is why your modules think they need to specify a logging system; in the case of gmaven I would guess because you are using it embedded but it can also run stand-alone.

GMaven is embedded in our build to generate Java stubs in a mixed Java/Groovy submodule. gmaven-runtime-1.7:1.3 brings in gmaven-runtime-support:1.3, which brings in gshell-io:2.0, which brings in gossip:1.0.

> In the case of the other module I would guess that it's a legacy one, and you should be using log4j-over-slf4j to redirect log4j to it (unless you actually want to use log4j).

The other module uses Magnolia CMS, which via a couple of links brings in both slf4j-log4j12 and jcl-over-slf4j according to mvn dependency:tree.

> You could try excluding gossip and log4j explicitly (by giving them "provided" scope) and choosing your own logging implementation such as logback.
>
> If you do not it will be an arbitrary consequence of classloading order as to which logging system (gossip of log4j) ends up handling any log calls to SLF4J.

Ok thanks, we'll look into this.

Is there anything which should be reported as a bug to either GMaven or Magnolia CMS, or is this just our combination of the two?

Nils.
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