What do you mean by "integrate"? What difficulty do you anticipate having server-side Java code act as a REST client, regardless what other frameworks are used?
What Tim said. Are you looking to implement rest with Struts? see the Struts REST plugin Are you asking how to learn Struts so you can extend an existing REST application? start with the Struts 2 FAQ Are you asking how to build and deploy applications on Tomcat? see here