Weld has a SL4J logger extension that will probably be user for Seam 3 also

Nicklas Karlsson wrote on Mar 27, 2010 18:50:


Weld has a SL4J logger extension that will probably be user for Seam 3 also

I'll make that statement more definitive. Seam 3 modules will use the SL4J logger extension :)

import org.slf4j.Logger;
...
@Inject Logger log;

Please be aware that there is currently a classloading problem with SLF4J that you may run into on JBoss AS. I'll explain the problem and the solution.

Problem

weld-extensions includes slf4j-api as a compile time dependency and Seam 3 modules (that use the logger extension) bring in weld-extensions. That means that slf4j-api will end up in your archive (by default). If you deploy just the API, you will get a startup error in JBoss AS 6.0 M2 because the SLF4J library is already on the server and exposed to the application.

Solution

The temporary solution is to include slf4j-jdk14 as a runtime dependency. This bridge to JDK logging prevents conflicts between the two SLF4J libraries. Seam 3 parent now includes slf4j-jdk14 as a runtime dependency as a sensible default until we can figure out the proper solution. (The other workaround would have been to exclude slf4j-api, but then you would be assuming that the server provides SLF4J -> non-portable).