WebSocketEndpoint.java

/**
 * diqube: Distributed Query Base.
 *
 * Copyright (C) 2015 Bastian Gloeckle
 *
 * This file is part of diqube.
 *
 * diqube is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.diqube.ui.websocket;

import java.util.Collection;

import javax.websocket.CloseReason;
import javax.websocket.EndpointConfig;
import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;

import org.diqube.ui.DiqubeServletContextListener;
import org.diqube.ui.websocket.request.JsonRequest;
import org.diqube.ui.websocket.request.JsonRequestDeserializer;
import org.diqube.ui.websocket.request.JsonRequestRegistry;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.ApplicationContext;

/**
 * Websocket endpoint that will be used by the JavaScript UI.
 * 
 * This endpoint is instantiated programatically, see {@link DiqubeServletContextListener}. For more information, see
 * JSR 356, v1.1, 6.4 "Programmatic Server Deployment".
 *
 * @author Bastian Gloeckle
 */
public class WebSocketEndpoint {
  private static final Logger logger = LoggerFactory.getLogger(WebSocketEndpoint.class);

  /** The URL mapping under which this endpoint will be available */
  public static final String ENDPOINT_URL_MAPPING = "/socket";

  /**
   * Property name in this endpoints {@link EndpointConfig#getUserProperties()} and in all
   * {@link Session#getUserProperties()} whose value is an {@link ApplicationContext}.
   */
  public static final String PROP_BEAN_CONTEXT = "diqube.springContext";

  @OnOpen
  public void onOpen(Session session, EndpointConfig config) {
    ApplicationContext ctx = (ApplicationContext) config.getUserProperties().get(PROP_BEAN_CONTEXT);
    session.getUserProperties().put(PROP_BEAN_CONTEXT, ctx);

    for (WebSocketEndpointListener listener : ctx.getBeansOfType(WebSocketEndpointListener.class).values()) {
      listener.socketOpened();
    }
  }

  @OnMessage
  public void onMessage(String msg, Session session) throws Exception {
    try {
      logger.trace("Received message on session {}: {}", session, msg);

      for (WebSocketEndpointListener listener : getBeanCtx(session).getBeansOfType(WebSocketEndpointListener.class)
          .values()) {
        listener.socketMessage();
      }

      JsonRequestDeserializer deserializer = getBeanCtx(session).getBean(JsonRequestDeserializer.class);
      JsonRequestRegistry requestRegistry = getBeanCtx(session).getBean(JsonRequestRegistry.class);
      JsonRequest request = deserializer.deserialize(msg, session);

      requestRegistry.registerRequest(session, request);

      request.executeCommand();
    } catch (Exception e) {
      logger.error("Exception on session {}. Swallowing.", session, e);
      // we must not re-throw the exception, otherwise the Websocket will be closed - we though do not want to do this
      // if just any command threw an exception.
    }
  }

  @OnClose
  public void onClose(Session session, CloseReason reason) {
    JsonRequestRegistry requestRegistry = getBeanCtx(session).getBean(JsonRequestRegistry.class);
    Collection<JsonRequest> requests = requestRegistry.getRequestsOfSession(session);
    logger.trace("Closing session {} because the websocket has been closed. This session has {} "
        + "open requests which will be cancelled.", session, requests.size());
    for (JsonRequest request : requests)
      try {
        request.cancel();
      } catch (RuntimeException e) {
        logger.warn("Could not cancel a request.", e);
      }
  }

  @OnError
  public void onError(Session session, Throwable throwable) {
    logger.trace("Received ERROR ({})", session, throwable);
  }

  private ApplicationContext getBeanCtx(Session session) {
    return (ApplicationContext) session.getUserProperties().get(PROP_BEAN_CONTEXT);
  }

  /**
   * Listener that is informed about activity on the websocket.
   */
  public static interface WebSocketEndpointListener {
    public void socketOpened();

    public void socketMessage();
  }
}