You have index.jsp in the web root folder. If you requested to show this folder, and web server found that there's index.jsp in that folder it redirects to index.jsp. This code is from Tomcat's web.xml:
<!-- ==================== Default Welcome File List ===================== -->
<!-- When a request URI refers to a directory, the default servlet looks -->
<!-- for a "welcome file" within that directory and, if present, to the -->
<!-- corresponding resource URI for display. -->
<!-- If no welcome files are present, the default servlet either serves a -->
<!-- directory listing (see default servlet configuration on how to -->
<!-- customize) or returns a 404 status, depending on the value of the -->
<!-- listings setting. -->
<!-- -->
<!-- If you define welcome files in your own application's web.xml -->
<!-- deployment descriptor, that list *replaces* the list configured -->
<!-- here, so be sure to include any of the default values that you wish -->
<!-- to use within your application. -->
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
If you remove index.jsp from the root folder, your code might work if it has correct mapping to the action. You might also find this question Can Struts 2 First Page come through the engine instead of listing it in and answer useful to you.