AVAJAVA Web Tutorials

In an earlier lesson, I described Log4j and initialized logging in a small test application using the BasicConfigurator class. This is a nice starting point, but a much more practical approach is to initialize log4j in an application using properties.

In your project, you need the log4j jarW file in the build path. I created a Log4JPropertiesTest class in this project.

Log4JPropertiesTest is a very simple class that we'll use as a starting point to test out configuring Log4j via properties.

Log4JPropertiesTest.java

package test;

import org.apache.log4j.Logger;

public class Log4JPropertiesTest {
	static Logger log = Logger.getLogger(Log4JPropertiesTest.class);

	public static void main(String[] args) {
		log.debug("This is a debug message");
		myMethod();
		log.info("This is an info message");
	}

	private static void myMethod() {
		try {
			throw new Exception("My Exception");
		} catch (Exception e) {
			log.error("This is an exception", e);
		}
	}
}

I created an EclipseSW Debug Configuration for Log4JPropertiesTest.

Since we want to really see what's going on with Log4j, let's add a VM argument instructing log4j to output additional information so we can tell what's going on behind the scenes. This argument is:

-Dlog4j.debug=true

If we click Debug, we can run our application. In the console window, we can see that log4j searches for a log4j.xml file and then searches for a log4j.properties file. It doesn't find either (since we haven't created either one of them), so it reports:

log4j: Could not find resource: [null].

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