Accessing HttpServletRequest properties within a WebSocket @ServerEndpoint

Question

I need to access the HttpServletRequest properties to get the javax.servlet.request.X509Certificate which contains the X509Certificate arr

Answer 1

Without hacking:

1. Create servlet filter on URL pattern matching websocket handshake request.
2. In filter, get request attribute of interest and put it in session before continuing chain.
3. Finally get it from the session which is in turn just available via handshake request.

With hacking:

1. Use reflection to find ServletRequest field in handshake request instance.

2. Get its javax.servlet.request.X509Certificate attribute.

   In other words:

   public class ServletAwareConfigurator extends Configurator {
   
       @Override
       public void modifyHandshake(ServerEndpointConfig config, HandshakeRequest request, HandshakeResponse response) {
           ServletRequest servletRequest = getField(request, ServletRequest.class);
           X509Certificate[] certificates = (X509Certificate[]) servletRequest.getAttribute("javax.servlet.request.X509Certificate");
           // ...
       }
   
       private static <I, F> F getField(I instance, Class<F> fieldType) {
           try {
               for (Class<?> type = instance.getClass(); type != Object.class; type = type.getSuperclass()) {
                   for (Field field : type.getDeclaredFields()) {
                       if (fieldType.isAssignableFrom(field.getType())) {
                           field.setAccessible(true);
                           return (F) field.get(instance);
                       }
                   }
               }
           } catch (Exception e) {
               // Handle?
           }
   
           return null;
       }
   
   }