The aim of the ant4eclipse project is to avoid (or at least: to reduce) the redundancy of Eclipse and Ant configurations. More precisly: it consists of Ant tasks that are able to read and work with some of Eclipse's configuration files. With these tasks you're able to:
Team Project Setfeature of eclipse
With all these tasks you're able to create a complete automatic build system that starts with checking out all required projects from CVS, builds all projects in the correct order with classpath settings as specified in Eclipse, and to launch your applications as they are specified in Eclipse. And the best of it: if you or someone else changes a configuration in Eclipse, those changes are immediately visible to your buildfiles - without changing one line of code!
For more information:
Recommend the tutorial