/*
* 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 net.zschech.gwt.comet.client.impl;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import net.zschech.gwt.comet.client.CometClient;
import net.zschech.gwt.comet.client.CometException;
import net.zschech.gwt.comet.client.CometListener;
import net.zschech.gwt.comet.client.CometSerializer;
import com.google.gwt.core.client.JsArrayString;
import com.google.gwt.dom.client.BodyElement;
import com.google.gwt.dom.client.IFrameElement;
import com.google.gwt.dom.client.Node;
import com.google.gwt.dom.client.NodeList;
import com.google.gwt.user.client.rpc.SerializationException;
import com.google.gwt.user.client.rpc.StatusCodeException;
/**
* This class uses IE's ActiveX "htmlfile" with an embedded iframe to stream events.
* http://cometdaily.com/2007/11/18/ie-activexhtmlfile-transport-part-ii/
*
* The main issue with this implementation is that we can't detect initial connection errors. A connection timer is
* setup to detect this.
*
* Another issues is that the memory required for the iframe constantly grows so the server occasionally disconnects the
* client who then reestablishes the connection with an empty iframe. To alleviate the issue the client removes script
* tags as the messages in them have been processed.
*
* The protocol for this transport is a stream of <script> tags with function calls to this transports callbacks as
* follows:
*
* c(heartbeat) A connection message with the heartbeat duration as an integer
*
* e(error) An error message with the error code
*
* h() A heartbeat message
*
* r() A refresh message
*
* m(string...) string and gwt serialized object messages
*
* string and gwt serialized object messages are Java Script escaped
*
* @author Richard Zschech
*/
public class IEHTMLFileCometTransport extends CometTransport {
private String domain;
private IFrameElement iframe;
private BodyElement body;
private boolean connected;
private boolean expectingDisconnection;
@Override
public void initiate(CometClient client, CometListener listener) {
super.initiate(client, listener);
domain = getDomain(getDocumentDomain(), client.getUrl());
StringBuilder html = new StringBuilder("<html>");
if (domain != null) {
html.append("<script>document.domain='").append(domain).append("'</script>");
}
html.append("<iframe src=''></iframe></html>");
iframe = createIFrame(this, html.toString());
}
@Override
public void connect(int connectionCount) {
expectingDisconnection = false;
String url = getUrl(connectionCount);
if (domain != null) {
url += "&d=" + domain;
}
iframe.setSrc(url);
}
@Override
public void disconnect() {
// TODO this does not seem to close the connection immediately.
expectingDisconnection = true;
iframe.setSrc("");
if (connected) {
onDisconnected();
}
}
private native IFrameElement createIFrame(IEHTMLFileCometTransport client, String html) /*-{
var htmlfile = new ActiveXObject("htmlfile");
htmlfile.open();
htmlfile.write(html);
htmlfile.close();
htmlfile.parentWindow.m = $entry(function(message) {
client.@net.zschech.gwt.comet.client.impl.IEHTMLFileCometTransport::onMessages(Lcom/google/gwt/core/client/JsArrayString;)(arguments);
});
htmlfile.parentWindow.c = $entry(function(heartbeat) {
client.@net.zschech.gwt.comet.client.impl.IEHTMLFileCometTransport::onConnected(I)(heartbeat);
});
htmlfile.parentWindow.d = $entry(function() {
client.@net.zschech.gwt.comet.client.impl.IEHTMLFileCometTransport::onDisconnected()();
});
htmlfile.parentWindow.e = $entry(function(statusCode, message) {
client.@net.zschech.gwt.comet.client.impl.IEHTMLFileCometTransport::onError(ILjava/lang/String;)(statusCode, message);
});
htmlfile.parentWindow.h = $entry(function() {
client.@net.zschech.gwt.comet.client.impl.IEHTMLFileCometTransport::onHeartbeat()();
});
htmlfile.parentWindow.r = $entry(function() {
client.@net.zschech.gwt.comet.client.impl.IEHTMLFileCometTransport::onRefresh()();
});
// no $entry() because no user code is reachable
htmlfile.parentWindow.t = function() {
client.@net.zschech.gwt.comet.client.impl.IEHTMLFileCometTransport::onTerminate()();
};
return htmlfile.documentElement.getElementsByTagName("iframe").item(0);
}-*/;
private native String getDocumentDomain() /*-{
return $doc.domain;
}-*/;
private native String getDomain(String documentDomain, String url) /*-{
var urlParts = /(^https?:)?(\/\/(([^:\/\?#]+)(:(\d+))?))?([^\?#]*)/.exec(url);
var urlDomain = urlParts[4];
if (!urlDomain || documentDomain == urlDomain) {
return null;
}
var documentDomainParts = documentDomain.split('.');
var urlDomainParts = urlDomain.split('.');
var d = documentDomainParts.length - 1;
var u = urlDomainParts.length - 1;
var resultDomainParts = [];
while (d >= 0 && u >= 0 && documentDomainParts[d] == urlDomainParts[u]) {
resultDomainParts.push(urlDomainParts[u]);
d--;
u--;
}
return resultDomainParts.reverse().join('.')
}-*/;
private void collect() {
NodeList<Node> childNodes = body.getChildNodes();
if (childNodes.getLength() > 1) {
body.removeChild(childNodes.getItem(0));
}
}
private void onMessages(JsArrayString arguments) {
collect();
int length = arguments.length();
List<Serializable> messages = new ArrayList<Serializable>(length);
for (int i = 0; i < length; i++) {
String message = arguments.get(i);
switch (message.charAt(0)) {
case ']':
messages.add(message.substring(1));
break;
case '[':
case 'R':
case 'r':
case 'f':
CometSerializer serializer = client.getSerializer();
if (serializer == null) {
listener.onError(new SerializationException("Can not deserialize message with no serializer: " + message), true);
}
else {
try {
messages.add(serializer.parse(message));
}
catch (SerializationException e) {
listener.onError(e, true);
}
}
break;
default:
listener.onError(new CometException("Invalid message received: " + message), true);
}
}
listener.onMessage(messages);
}
private void onConnected(int heartbeat) {
connected = true;
body = iframe.getContentDocument().getBody();
collect();
listener.onConnected(heartbeat);
}
private void onDisconnected() {
connected = false;
body = null;
if (expectingDisconnection) {
listener.onDisconnected();
}
else {
listener.onError(new CometException("Unexpected disconnection"), false);
}
}
private void onError(int statusCode, String message) {
listener.onError(new StatusCodeException(statusCode, message), false);
}
private void onHeartbeat() {
listener.onHeartbeat();
}
private void onRefresh() {
listener.onRefresh();
}
private void onTerminate() {
expectingDisconnection = true;
}
}