Java tutorial
/* * Copyright 2011 Jeanfrancois Arcand * * Licensed under the Apache License, Version 2.0 (the "License"); you may not * use this file except in compliance with the License. You may obtain a copy of * the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations under * the License. */ /* * Copyright 2009 Richard Zschech. * * Licensed under the Apache License, Version 2.0 (the "License"); you may not * use this file except in compliance with the License. You may obtain a copy of * the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations under * the License. */ package org.atmosphere.gwt.client.impl; import com.google.gwt.core.client.JavaScriptException; import com.google.gwt.dom.client.NativeEvent; import com.google.gwt.event.dom.client.KeyCodes; import com.google.gwt.event.dom.client.KeyDownEvent; import com.google.gwt.http.client.RequestException; import com.google.gwt.user.client.Event; import com.google.gwt.user.client.Event.NativePreviewEvent; import com.google.gwt.user.client.Event.NativePreviewHandler; import com.google.gwt.user.client.Timer; import com.google.gwt.xhr.client.ReadyStateChangeHandler; import com.google.gwt.xhr.client.XMLHttpRequest; /** * This class uses a XmlHttpRequest and onreadystatechange events to process stream events. * * The main issue with this implementation is that GWT does not generate RECEIVING events from its XMLHTTPRequest. The * implementation of XMLHTTPRequest included in this package overrides that behaviour. * * Another issues is that the memory required for the XMLHTTPRequest's responseText constantly grows so the server * occasionally disconnects the client who then reestablishes the connection. * * The protocol for this transport is a '\n' separated transport messages. The different types of transport message are * identified by the first character in the line as follows: * * ! A connection message followed by the heartbeat duration as an integer * * ? A clean server disconnection message * * # A heartbeat message * * * A padding message to cause the browser to start processing the stream * * ] A string message that needs unescaping * * | A string message that does not need unescaping * * [ A GWT serialized object * * R, r or f A GWT deRPC object * * string messages are escaped for '\\' and '\n' characters as '\n' is the message separator. * * GWT serialized object messages are escaped by GWT so do not need to be escaped by the transport * * @author Richard Zschech */ public class HTTPRequestCometTransport extends StreamingProtocolTransport { /** * Fix dropping RPC request when hitting ESC in firefox * @see http://is.gd/dDeGQ */ static { Event.addNativePreviewHandler(new NativePreviewHandler() { @Override public void onPreviewNativeEvent(NativePreviewEvent e) { if (e.getTypeInt() == Event.getTypeInt(KeyDownEvent.getType().getName())) { NativeEvent nativeEvent = e.getNativeEvent(); if (nativeEvent.getKeyCode() == KeyCodes.KEY_ESCAPE) { nativeEvent.preventDefault(); } } } }); } private final static int POLLING_INTERVAL = 250; private XMLHttpRequest xmlHttpRequest; private Timer pollingTimer = new Timer() { @Override public void run() { if (xmlHttpRequest != null && read < xmlHttpRequest.getResponseText().length()) { onReceiving(xmlHttpRequest.getStatus(), xmlHttpRequest.getResponseText()); } } }; @Override public void connect(int connectionCount) { init(); xmlHttpRequest = XMLHttpRequest.create(); try { xmlHttpRequest.open("GET", getUrl(connectionCount)); xmlHttpRequest.setRequestHeader("Accept", "application/comet"); xmlHttpRequest.setOnReadyStateChange(new ReadyStateChangeHandler() { @Override public void onReadyStateChange(XMLHttpRequest request) { if (!aborted) { switch (request.getReadyState()) { case XMLHttpRequest.LOADING: onReceiving(request.getStatus(), request.getResponseText()); if (needPolling()) { pollingTimer.scheduleRepeating(POLLING_INTERVAL); } break; case XMLHttpRequest.DONE: onLoaded(request.getStatus(), request.getResponseText()); pollingTimer.cancel(); break; } } else { request.clearOnReadyStateChange(); if (request.getReadyState() != XMLHttpRequest.DONE) { request.abort(); } } } }); xmlHttpRequest.send(); } catch (JavaScriptException e) { if (xmlHttpRequest != null) { xmlHttpRequest.abort(); xmlHttpRequest = null; } listener.onError(new RequestException(e.getMessage()), false); } } @Override public void disconnect() { aborted = true; expectingDisconnection = true; super.disconnect(); if (xmlHttpRequest != null) { if (xmlHttpRequest.getReadyState() >= XMLHttpRequest.HEADERS_RECEIVED) { // if readystate >= HEADERS_RECEIVED we can abort otherwise wait for this in onReadyStateChange xmlHttpRequest.clearOnReadyStateChange(); if (xmlHttpRequest.getReadyState() != XMLHttpRequest.DONE) { listener.onDisconnected(); xmlHttpRequest.abort(); } xmlHttpRequest = null; } else { new Timer() { XMLHttpRequest r = xmlHttpRequest; @Override public void run() { r.clearOnReadyStateChange(); if (r.getReadyState() != XMLHttpRequest.DONE && r.getReadyState() != XMLHttpRequest.UNSENT) { listener.onDisconnected(); r.abort(); } r = null; } }.schedule(5000); xmlHttpRequest = null; } } } protected boolean needPolling() { String ua = getUserAgent(); return ua.contains("opera"); } /** * Returns the browser's user agent. * * @return the user agent */ public native static String getUserAgent() /*-{ return $wnd.navigator.userAgent.toLowerCase(); }-*/; private void onLoaded(int statusCode, String responseText) { xmlHttpRequest.clearOnReadyStateChange(); xmlHttpRequest = null; onReceiving(statusCode, responseText, false); } private void onReceiving(int statusCode, String responseText) { onReceiving(statusCode, responseText, true); } }