Enabling websockets in spark with @davidvollmar 's socket and servlet adapters combined with an altered way to mount the rest of the handlers.

WebSocketExample.java

package spark;

import org.eclipse.jetty.servlet.ServletContextHandler;

public class WebSocketExample
{
  public static void main(String[] args)
  {
    setupSpark();
    Spark.get("/", (request, response) -> "Hello");
    initializeWebsocket();
  }

  public static void setupSpark()
  {
    Spark.port(8888);
  }

  public static void initializeWebsocket()
  {
    ServletContextHandler servletContextHandler = new ServletContextHandler(null, "/", true, false);
    servletContextHandler.addServlet(MyEchoServlet.class, "/sock");

    boolean ok = false;
    while(!ok)
    {
      ok = WebSockets.addExternalHandler(servletContextHandler);
    }

    System.out.println("WebSocket Handler Initialized");
  }
}

WebSockets.java

package spark;

import org.apache.commons.lang3.reflect.FieldUtils;
import org.eclipse.jetty.server.Handler;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.server.handler.HandlerList;
import spark.webserver.SparkServer;

import java.util.ArrayList;
import java.util.List;

public final class WebSockets
{
  public static boolean addExternalHandler(Handler handler)
  {
    List<Handler> h = new ArrayList<>();
    h.add(handler);

    return addExternalHandlers(h);
  }

  public static boolean addExternalHandlers(List<Handler> handlers)
  {
    SparkServer ss = Spark.server;

    if(ss != null)
    {
      Server js = null;
      try
      {
        js = (Server) FieldUtils.readDeclaredField(ss, "server", true);
      }
      catch (IllegalAccessException e)
      {
        // TODO: Nope Nope Nope
      }

      if(js != null)
      {
        Handler raw_handler = js.getHandler();

        // Already a handler list.
        if(raw_handler instanceof HandlerList)
        {
          HandlerList hl = (HandlerList) raw_handler;

          if(hl != null)
          {
            for(Handler h : handlers)
              hl.addHandler(h);

            return true;
          }
        }
        else
        {
          try
          {
            Handler jettyHandler = (Handler) FieldUtils.readDeclaredField(ss, "handler", true);

            if(jettyHandler != null)
            {
              List<Handler> handlersInList = new ArrayList<>();

              // External Handlers First
              handlersInList.addAll(handlers);
              handlersInList.add(jettyHandler);

              HandlerList newHandlers = new HandlerList();
              newHandlers.setHandlers(handlersInList.toArray(new Handler[handlersInList.size()]));
              js.setHandler(newHandlers);

              return true;
            }
          }
          catch (IllegalAccessException e)
          {
            // TODO: nope Nope nope. :D
          }
        }
      }
    }

    return false;
  }
}

Don't know, did this a while ago because the existing snippet to hack in didn't work.

Is this a functional websocket example for spark?

Where is the MyEchoServlet class?