Eclipse RCP : Redirecting eclipse errors to log4j

Its sometimes tedious to find the real exception occured when using an eclipse based application. Since it goes under the workspace/.metadata/.log file. It takes a while to figure this out. But most of the desktop application do write to a log file of its own. So when using eclipse using two log files to know about the application is kind of not nice.

But still eclipse provides a way to listen to the log messages of its own. So if the application uses its own logging , it can listen to the eclipse log and add it to its own logger. Here we will look at connecting eclipse log messages to the log4j logger.

Eclipse Platform provides a method to add listeners Platform.addLogListener(ILogListener);

So how do we add the listener to the Platform. In the Activator of the application plugin's start method, add the following.

public class Activator extends AbstractUIPlugin {

  private ILogListener listener;


  @Override
  public void start(final BundleContext context) throws Exception {
      super.start(context);
      plugin = this;
      listener = new Listener();
      Platform.addLogListener(listener);
  }

  @Override
  public void stop(final BundleContext context) throws Exception {
      Platform.removeLogListener(listener);
      listener = null;
      plugin = null;
      super.stop(context);
  }

}

Now every error/warning eclipse logs to its .log file under .metadata directory will be sent to the log listener. How does the log listener handle the events from the eclipse?

   package  com.logging;
   public class Listener implements ILogListener {
      private static final Logger LOGGER = Logger.getLogger(Listener.class.getName());

      @Override
      public void logging(final IStatus status, final String plugin) {
          if (status.getSeverity() == IStatus.WARNING) {
              if (status.getException() == null) {
                  LOGGER.warn(status.getMessage());
              } else {
                  LOGGER.warn(status.getMessage() + status.getException());
              }
          } else if (status.getSeverity() == IStatus.ERROR) {
              if (status.getException() == null) {
                  LOGGER.error(status.getMessage());            
              } else {
                  LOGGER.error(status.getMessage()+status.getException());
              }
          }
      }
  }

Now all the eclipse errors and warnings will go to the logger which is configured for Listener.class.getName().

To get all the log messages from the eclipse. the log4j.properties

log4j.category.com.logging.Listener=all

This will log all the errors and warnings from the eclipse application to the log4j's log file or console as configured.