Eclipse only provides a basic, yet awesome, Java development environment. To write J2EE applications, you need to download and install some eclipse plugins, many of which can be found at www.eclipse.org
Downloading and installing all of these can be a challenge, although the challenge is typically finding the ones you like best. MyEclipseIDE provides all of the basic plugins for about $35, or a professional version at $50. Depending upon how valuable your time is, you might want to get with myeclipseide.