[jira] [Commented] (FELIX-5310) Felix HTTP Jetty WebSockets do not work out of the box

["Carsten Ziegeler (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FELIX-5310?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16010020#comment-16010020 ] 

Carsten Ziegeler commented on FELIX-5310:
-----------------------------------------

I guess we could solve the TCCL problem by setting it before calling init() of any servlet in the implementation.
Not sure what exactly the other problem is, I assume some initialization is missing when init() is called. One way out would be to call init() lazy as well from within the http implementation instead of doing it when the servlet is registered. While this would be a nice thing anyway, it will require some changes. So if there is a easier way out for this specific problem, we should probably go there

> Felix HTTP Jetty WebSockets do not work out of the box
> ------------------------------------------------------
>
>                 Key: FELIX-5310
>                 URL: https://issues.apache.org/jira/browse/FELIX-5310
>             Project: Felix
>          Issue Type: Bug
>          Components: HTTP Service
>    Affects Versions: http.jetty-3.2.0
>            Reporter: Timothy Ward
>
> I have encountered two significant problems when trying to use the Jetty WebSocketServlet with the Jetty based Felix HTTP service whiteboard. Both problems occur in the init method of my servlet.
>  1. I have to set the TCCL for the Jetty Web Socket implementation to be able to find its own internal implementation of Websockets (specifically org.eclipse.jetty.websocket.server.WebSocketServerFactory). This is really stupid, as the TCCL I have to use is the Felix HTTP Jetty bundle's class loader!
> 2. The Jetty Web Socket implementation does one (and only one) check to check that it's running on Jetty. It looks as though the only reason for this is to get hold of an Executor which is available via a getter. This check involves trying to establish the Jetty Context by casting the ServletContext to a Jetty internal type. This does not work as the HTTP Whiteboard wrappers the ServletContext. I can work around this by delaying initialisation to the first request so that there is a context to get hold of, but this also sucks :(
> In summary, my servlet has to look like this, most of which should not be necessary!
> {code:java}
>     public class EchoServlet extends WebSocketServlet {
>     
>         private static final Logger LOGGER = LoggerFactory.getLogger(EchoServlet.class);
>     
>         private final AtomicBoolean firstCall = new AtomicBoolean(true); 
>     
>         private final CountDownLatch initBarrier = new CountDownLatch(1); 
>     
>         @Override
>         public void init() throws ServletException {
>             LOGGER.info("The Echo servlet has been initialized, but we delay initialization until the first request so that a Jetty Context is available");	
>         }
> 	
>         @Override
>         public void service(ServletRequest arg0, ServletResponse arg1) throws ServletException, IOException {
>             if(firstCall.compareAndSet(true, false)) {
>                 try {
>                     delayedInit();
>                 } finally {
>                     initBarrier.countDown();
>                 }
>             } else {
>                 try {
>                     initBarrier.await();
>                 } catch (InterruptedException e) {
>                     throw new ServletException("Timed out waiting for initialisation", e);
>                 }
>             }
> 		
>             super.service(arg0, arg1);
>         }
>         private void delayedInit() throws ServletException {
>             // Overide the TCCL so that the internal factory can be found
>             // Jetty tries to use ServiceLoader, and their fallback is to
>             // use TCCL, it would be better if we could provide a loader...
> 		
>             Thread currentThread = Thread.currentThread();
>             ClassLoader tccl = currentThread.getContextClassLoader();
>             currentThread.setContextClassLoader(WebSocketServlet.class.getClassLoader());
>             try {
>                 super.init();
>             } finally {
>                 currentThread.setContextClassLoader(tccl);
>             }
>         }
>         @Override
>         public void configure(WebSocketServletFactory wsf) {
>             wsf.setCreator((req,res) -> new WebSocketAdaptor() {
>                     public void onWebSocketText(String message) {
>                         getRemote().sendStringByFuture("Echo: " + message);
>                     }
>                 });
>         }
>     }
> {code}



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