Testing and Debugging Your Web Applications
Once you have a correctly configured server, you can run your application directly from within Eclipse using "Run As -> Run on Server". Eclipse will start the application server and deploy your application, displaying logging messages to the Eclipse console and the application Web page within the Eclipse IDE.
You can also debug your Web applications very easily using "Debug As -> Debug on Server". This will run your application in the debug perspective. This perspective lets you insert breakpoints into your JSP pages, inspect variables, and step through the page-generation process, just as you would a normal class.
Eclipse Does Web Development
The WTP toolset represents a major step forward for Eclipse in the domain of Web development.
Granted, many of the features existed before WTP, dispersed among other third-party plug-ins with varying degrees of quality and reliability. However, the WTP project brings these features together in a coherent, reliable, well-integrated group, and it makes them easily available in the standard Eclipse installation.
In all fairness, other similar products exist for Eclipse, including feature-rich commercial products such as Exadel Studio Pro, BEA Workshop, and MyEclipse. In fact, these products build on WTP, providing extra features such as better support for JSF and support for other open source projects such as Spring and Hibernate.
In any case, if you are developing Java Web applications with Eclipse, you stand to gain a great deal by understanding what WTP has to offer. Take a look!