【java struts2】Filters vs Interceptors in Struts 2

The most significant difference is that "interceptors" are a part of the Struts 2 framework, and are only part of the request handling that is done by the Struts 2 framework. "Filters" on the other hand are a part of the Servlet Specifcation; in other words, they are part of the Servlet API. If you are using Struts 2, you should use interceptors for wrapping functionality around your Struts 2 actions. If you are trying to wrap functionality around requests coming to your webapp, but not being handled by Struts 2, then a filter might be more appropriate.

BTW, the entire Struts 2 Framework is deployed inside a filter configured in your web app, declared in your webapp's deployment descriptor ( web.xml ) like:

<filter>
        <filter-name>struts2</filter-name>
        <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
    </filter>

     <filter-mapping>
        <filter-name>struts2</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

　　This filter, which is configured to catch all requests URL patterns, is the entry point into the entire Struts 2 framework.