Re: Serious letdown when trying to log4j in Tomcat. Unsolvable? (Solved)

[David Tonhofer, m-plify S.A.]

--On Monday, January 12, 2004 11:27 PM -0600 Jacob Kjome <[EMAIL PROTECTED]> 
wrote:

The gist:

 "In some (most?) cases you cannot use a 'log4j.properties'
  file placed in your web application's WEB-INF/classes
  directory"

Who are you quoting?
Well, myself of course ;-)

...this goes counter to the Log4J's documentation, which says:

 "The default log4j initialization is particularly useful in web-server
 environments. Under Tomcat 3.x and 4.x, you should place the
 log4j.properties under the WEB-INF/classes directory of your
 web-applications. Log4j will find the properties file and initialize
 itself. This is easy to do and it works."

Well, it works fine....as long as you *also* add log4j.jar to WEB-INF/lib.
I bet you didn't do that, did you. :-)
Actually, no.

True, WEB-INF/classes/log4j.properties is irrelevant to 
common/lib/log4j.jar.
However, it is *entirely* relevant to WEB-INF/lib/log4j.jar.  Because of 
the
class loading behavior of webapps, any webapp with log4j.jar in its own
WEB-INF/lib will run its default logger repository in an entirely
self-contained environment completely separated from that of the server or
other apps.
Ah...good idea! I didn't think of that. The "greedy" webapp classloader
will have its own log4j 'universe' (classes *and* logging hierarchy), while
classloaders higher up the classloader hierarchy are unaffected. You must
not forget to also add commons-logging jars if you log through 
commons-logging.

Thus, let's summarize:

Default setup for Tomcat:

 tomcat4.1.24/common/lib/commons-logging.jar
 tomcat4.1.24/common/lib/commons-logging-api.jar
 tomcat4.1.24/common/lib/log4j.jar
 tomcat4.1.24/common/classes/log4j.properties
Setup for webapp using commons-logging with log4j underneath:

 my_webapp/WEB-INF/lib/commons-logging.jar
 my_webapp/WEB-INF/lib/commons-logging-api.jar
 my_webapp/WEB-INF/lib/log4j.jar
 my_webapp/WEB-INF/classes/log4j.properties
Once Tomcat starts up, commons-logging and log4j initialization (if any)
will be done through the Common classloader and the log4j.properties
file accessible to the common classloader. All classes loaded from the
Shared, Catalina and Common classloaders will 'see' that setup.
Once the webapp starts up, the Webapp classloader (greedy) will
restart its own initialization of commons-logging and log4j as these
classes are directly available to it. It will use the log4j.properties
file in its classes subdirectory. All classes loaded by the Webapp
classloader will 'see' that setup.
Classloader reference:

      Bootstrap
          |
       System
          |
          |
       Common
        /  \
       /    \
      /      \
  Catalina    |
           Shared
             / \
            /   \
      Webapp1  Webapp2
Jake
Thanks Jake.

David.

P.S. But shouldn't there be a notice in the log4j documentation?







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