title: How to set Async-Supported flag for the Filters which are getting called via Spring DelegatingFilterProxy chain?
body: <p>I am developing a servlet which will support Async operation.
  This servlet will be called via multiple filters. Some of the filters are as part of FilterProxyChain which is created via DelegatingFilterProxy.</p>
  
  <p>If we have to start an Async Context from a servlet, then the Filter Chain should also support Async operation. Else below exception gets thrown - </p>
  
  <blockquote>
    <p>28-Jul-2017 09:41:51.196 SEVERE [http-nio-127.0.0.1-7441-exec-2] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [eventBus] in context with path [] threw exception
     java.lang.IllegalStateException: A filter or servlet of the current chain does not support asynchronous operations.
            at org.apache.catalina.connector.Request.startAsync(Request.java:1630)
            at org.apache.catalina.connector.Request.startAsync(Request.java:1623)
            at org.apache.catalina.connector.RequestFacade.startAsync(RequestFacade.java:1030)
            at javax.servlet.ServletRequestWrapper.startAsync(ServletRequestWrapper.java:379)
            at javax.servlet.ServletRequestWrapper.startAsync(ServletRequestWrapper.java:379)
            at org.springframework.security.web.servletapi.HttpServlet3RequestFactory$Servlet3SecurityContextHolderAwareRequestWrapper.startAsync(HttpServlet3RequestFactory.java:167)
            at com.amdocs.vshield.vsm.asyncrest.VsmAsyncRestController.doGet(VsmAsyncRestController.java:89)
            at javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
            at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
            at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292)
            at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)</p>
  </blockquote>
  
  <p>Some of the filters which are called via DelegatingFilterProxy are not configured in web.xml explicitly.
  So how to make these filters to support Async ?</p>