Jakarta Struts Cookbook

13.3. Adding Logging to Your Own Classes

Problem

You want to log messages of varying severity from your own classes.

Solution

Use Commons Logging within your own classes, as shown in Example 13-3.

Example 13-3. Using Commons Logging in a custom class

package com.fooware.barapp;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

public class MyClazz {

    private static Log log = LogFactory.getLog(MyClazz.class);

    public void doSomething( ) {
        log.debug("About to do something.");
        try {
            //call something that throws an exception
        } catch (Exception e) {
            log.error("An exception occured doing something.", e);
        }
        log.info("Successfully did something.");
    }
}

Discussion

Any critical application should use logging of some kind. Relying on System.out.println( ) limits logging flexibility and can significantly downgrade application performance. You can roll your own logging mechanism, as many shops have done, or you can take advantage of frameworks and APIs such as Log4J and Commons Logging that make logging easy.

The Solution uses the Commons Logging API. Messages are logged to a logging category. If you use the class name as the category, you can control logging at the class level. In addition, you can use the package name as a hierarchy. The Commons Logging API supports the following logging levels in increasing order of severity:

1. Trace

2. Debug

3. Info

4. Warn

5. Error

6. Fatal

Using Commons Logging gives you the flexibility of choosing a logging implementation as desired. If you were using ...