You have a lot of options for developing Struts using Eclipse.
If it's important to you to have a 100% free toolset, go to:
http://www.eclipse.org/downloads/index_project.php And download the Web Tools Platform Project. You will also find instructions for dowloading and installation at this site.
I have found these tools to be a bit buggy and not easy to install.
If you're willing to pay, there are a number of commercial plugins available. The cheapest, and in my opinion the best value is MyEclipse available at:
http://www.myeclipseide.com/ It costs $29.95 per year, and has a lot of very handy features.