add build observer.

CupPlugin/src/de/tum/in/www2/cupplugin/Activator.java

 package de.tum.in.www2.cupplugin;
 
+import org.eclipse.core.resources.IResourceChangeEvent;
+import org.eclipse.core.resources.IResourceChangeListener;
+import org.eclipse.core.resources.ResourcesPlugin;
 import org.eclipse.jface.resource.ImageDescriptor;
 import org.eclipse.ui.plugin.AbstractUIPlugin;
 import org.osgi.framework.BundleContext;
 
+import org.eclipse.core.resources.IWorkspace;
+
 /**
  * The activator class controls the plug-in life cycle
  */
 public class Activator extends AbstractUIPlugin {
 
+	   public class DebugListener implements IResourceChangeListener {
+		   public void resourceChanged(IResourceChangeEvent event) {
+
+			   System.out.println("GOT EVENT: " + event.getType());			   
+			   if (event.getType() != IResourceChangeEvent.POST_BUILD)
+		            return;
+				   System.out.println("GOT POST BUILD EVENT!");
+	
+		      }
+	}
+
 	// The plug-in ID
 	public static final String PLUGIN_ID = "CupPlugin"; //$NON-NLS-1$
 
@@ -19,6 +35,8 @@ public class Activator extends AbstractUIPlugin {
 	 * The constructor
 	 */
 	public Activator() {
+		IWorkspace workspace = ResourcesPlugin.getWorkspace();
+		workspace.addResourceChangeListener(new DebugListener());
 	}
 
 	/*