you can download the FlexModule_j2ee.zip file from the adobe sit, unzip the file and it has the needed jars
According to my understanding you want to integrate flex with Struts, then what is the need of the Flex tag library when you want to integrate Flex with Struts. Directly at Flex side you can use the HttpService to call a Servlet or a Struts based Servlet then there is no need to use FlexTag Library. Also the jsp is the Presentation layer its not a good idea to use the Business logics in the JSP.This is what i Feel.
Here are some links that shows how to integrate Flex and Struts.
Any suggestions to me are purely welcome