Log4j - configuration file

Question

where can I find a guide on log4j?
I need to configure the logger, in a configuration file.
I've done it by a init servlet and a configuration file,but tomcat write this message
log4j:WARN No appenders could be found for logger (org.apache.commons.digester.Digester).
log4j:WARN Please initialize the log4j system properly.
the servlet is this:
package fromBegin.controller;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.log4j.PropertyConfigurator;
public class StartUpServlet extends HttpServlet
public void init() {
String prefix = getServletContext().getRealPath("/");
String file = getInitParameter("log4j-init-file");
// if the log4j-init-file is not set, then no point in trying
if(file != null) {
PropertyConfigurator.configure(prefix+file);
public
void doGet(HttpServletRequest req, HttpServletResponse res) {
the web.xml fragment is this
<servlet>
<servlet-name>startUp</servlet-name>
<servlet-class>fromBegin.controller.StartUpServlet</servlet-class>
<init-param>
<param-name>log4j-init-file</param-name>
<param-value>WEB-INF/log4j.lcf</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
and the configuration file is this:
# file di configurazione per la registrazione dei log
# mediante log4j
log4j.rootLogger=DEBUG, R
log4j.appender.R=org.apache.log4j.RollingFileAppender
log4j.appender.R.File=C:\\Documents and Settings\\Romeo\\Desktop\\Raccolta log\\log4j-track.log
log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%-4r [%t] %-5p %c %x - %m%n
finally,
anybody knows a online guide for log4j?
why tomcat give me that warning message?
thanks

Answer 1

The error message is coming because some other classes that use log4j debugging can't find your properties file.
In this case the org.apache.commons.digester.Digester.
It knows nothing about your personal log4j file for your app - you passed that in as a servlet ini parameter.
That will set up log4j to work for your code, but probably not for others.
Quick and dirty fix: put another log4j.properties file in your web-inf/classes directory. This will be found by all other applications wanting to use log4j. You can then set their logging levels in this file, seperate from your own.
Re online log4j documentation- http://logging.apache.org/log4j/docs/documentation.html
You most probably found that already though :-)
Good luck,
evnafets