The Google Plugin for Eclipse makes it easy to create new projects that use GWT and App Engine. It's also easy to set up your existing projects to make use of the plugin.
Importing your application into Eclipse
Create an Eclipse project for your source, if you haven't already done so, by selecting File > New > Java Project. Then choose Create project from existing source and set up your project. At this point, your source will be loaded in Eclipse, but the project's build path may not be set up properly, and you may see build errors.
Alternatively, if your application's source tree already contains a
.project file, either because you had previously worked on it in
Eclipse or because it was generated by a tool like GWT's webAppCreator,
you can import the project by going to File > Import >
General and selecting Existing Projects into
Enabling Google SDKs if your project already has a WAR directory
To enable Google Web Toolkit, right-click your project and select Google > Web Toolkit Settings. Check the Use Google Web Toolkit box and click OK to apply the change.
Enabling App Engine for your project is similar: right-click your project and select Google > App Engine Settings. Check the Use Google App Engine box and click OK.
Finally, open project properties and navigate to Google > Web Application and check the box for This project has a WAR directory and then enter the project-relative path to your WAR directory.
If your project depends on libraries not provided by the GWT and App Engine
SDKs, put them in
<WAR>/WEB-INF/lib and add them to your Java build
path. This approach should work for most existing Java web
applications, including server-side Java applications (such as those made
from the App Engine template), and GWT 1.6 or later projects.