For debugging a Java Web Application (e.g. SWAMP) the Servlet Container can be run directly in Eclipse. You need the "Sysdeo Tomcat Plugin" for Eclipse from here: http://www.sysdeo.com/eclipse/tomcatPlugin.html (MIT License) After copying the Sysdeo Files to your Eclipse/plugins folder and restarting Eclipse there are some new Options available. At first, add the Tomcat Controls to your Menubar with Window->Customize Perspective->Commands->Tomcat. Then you have to configure the Tomcat startup options in Window->Preferences->Tomcat.
Now you can startup tomcat with the toolbar button. The output is captured in eclipse's console window. To start debugging simply set a beakpoint in the source file that is going to be debugged. For a short introduction into the Eclipse Debugger yuo may look here: http://www-106.ibm.com/developerworks/opensource/library/os-ecbug/?Open&ca=daw-ec-dr