Ways to configure Log4j XML Configuration

Ways to configure Log4j XML Configuration

I am using log4j to log information in my web application. I have chosen
log4j.xml type of configuration instead of log4j.properties. I remember
that, for log4j.properties configuration, I did not write Java code lines
to find the log4j.property file location. However, for log4j.xml file
configuration I am specifying explicitly to find it like this
DOMConfigurator.configure("log4j.xml");//it reads file from classpath,
working!
Also, tested my application removing the above statement from source. It
doesn't see to work. None of the debug statements were printed except
System.out.println();
I have read that log4j by default looks for log4jproperties file or
log4j.xml file in the classpath. I checked in the deployed web
application, log4j.xml file is in web-inf/classes. Even though it can't
find log4j.xml.
Is it that, the above code line is mandatory for log4j xml configuration
in Java? In fact, can't Java source code doesn't pickup log4j.xml from the
classpath without explicit specification as above?