See Chapter 3, Debugging Applications, in Sun GlassFish Enterprise Server v3 Prelude Developer’s Guide.
Enterprise Server v3 Prelude and NetBeans 6.5 enable you to move applications that run on Tomcat using TopLink/EclipseLink to Enterprise Server. As a start, see “Moving Tomcat Toplink Apps to GlassFish v3 Prelude” (http://blogs.sun.com/Lance/entry/moving_tomcat_toplink_apps_to).