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CometD (bayeux) implementation of Wicketstuff Push
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.wicketstuff.push.cometd;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.UUID;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import org.apache.wicket.Application;
import org.apache.wicket.ResourceReference;
import org.apache.wicket.ajax.AbstractDefaultAjaxBehavior;
import org.apache.wicket.ajax.AjaxRequestTarget;
import org.apache.wicket.markup.html.IHeaderResponse;
import org.apache.wicket.markup.html.resources.CompressedResourceReference;
import org.apache.wicket.markup.parser.XmlPullParser;
import org.apache.wicket.markup.parser.XmlTag;
import org.apache.wicket.protocol.http.WebApplication;
import org.apache.wicket.util.template.PackagedTextTemplate;
import org.cometd.server.CometdServlet;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.wicketstuff.push.IPushEventHandler;
import org.wicketstuff.push.IPushNode;
/**
* This behavior will be asked by client side when it will receive a cometd event associated with
* the kind of event
*
* There is currently no support for multiple cometd servlets. It is not possible to override which
* URL to use via the {@link #getCometdServletPath()} overridable method. But two cometd instances
* cannot be used simultaneously.
*
* @author Xavier Hanin
* @author Rodolfo Hansen
* @author Sebastian Thomschke
*/
@SuppressWarnings({ "rawtypes", "unchecked" })
public class CometdPushBehavior extends AbstractDefaultAjaxBehavior
{
private static final long serialVersionUID = 1L;
private static final Logger LOG = LoggerFactory.getLogger(CometdPushBehavior.class);
private static final String DEFAULT_COMETD_PATH = guessCometdServletPath();
private static final ResourceReference COMETD = new CompressedResourceReference(
CometdPushBehavior.class, "js/cometd.js");
private static final ResourceReference COMETD_ACK = new CompressedResourceReference(
CometdPushBehavior.class, "js/cometd/AckExtension.js");
private static final ResourceReference COMETD_RELOAD = new CompressedResourceReference(
CometdPushBehavior.class, "js/cometd/ReloadExtension.js");
private static final ResourceReference COMETD_TIMESTAMP = new CompressedResourceReference(
CometdPushBehavior.class, "js/cometd/TimeStampExtension.js");
private static final ResourceReference COMETD_TIMESYNC = new CompressedResourceReference(
CometdPushBehavior.class, "js/cometd/TimeSyncExtension.js");
private static final PackagedTextTemplate TEMPLATE_INIT = new PackagedTextTemplate(
CometdPushBehavior.class, "CometdPushInit.js");
private static final PackagedTextTemplate TEMPLATE_EVENT_HANDLER = new PackagedTextTemplate(
CometdPushBehavior.class, "CometdPushEventHandlerTemplate.js");
private static final PackagedTextTemplate TEMPLATE_SUBSCRIBE = new PackagedTextTemplate(
CometdPushBehavior.class, "CometdPushSubscribeTemplate.js");
/**
* Parse the web.xml to find cometd context Path. This context path will be cache for all the
* application
*
* @return cometd context path
*/
private static String guessCometdServletPath()
{
final ServletContext servletContext = ((WebApplication)Application.get()).getServletContext();
final InputStream is = servletContext.getResourceAsStream("/WEB-INF/web.xml");
/*
* get the servlet name from class assignable to org.mortbay.cometd.CometdServlet
*/
try
{
final XmlPullParser parser = new XmlPullParser();
parser.parse(is);
String urlPattern = null;
while (true)
{
XmlTag elem;
// go down until servlet is found
do
elem = (XmlTag)parser.nextTag();
while (elem != null && !(elem.getName().equals("servlet") && elem.isOpen()));
// stop if elem is null
if (elem == null)
break;
// get the servlet name for org.mortbay.cometd.CometdServlet
String servletName = null, servletClassName = null;
do
{
elem = (XmlTag)parser.nextTag();
if (elem.isOpen())
parser.setPositionMarker();
else if (elem.isClose() && elem.getName().equals("servlet-name"))
servletName = parser.getInputFromPositionMarker(elem.getPos()).toString();
else if (elem.isClose() && elem.getName().equals("servlet-class"))
servletClassName = parser.getInputFromPositionMarker(elem.getPos())
.toString();
}
while (servletClassName == null ||
!CometdServlet.class.isAssignableFrom(Class.forName(servletClassName)));
if (servletName == null)
break;
// go down until servlet-mapping is found
do
elem = (XmlTag)parser.nextTag();
while (elem != null && !(elem.getName().equals("servlet-mapping") && elem.isOpen()));
// stop if elem is null
if (elem == null)
break;
// get the servlet name for org.mortbay.cometd.CometdServlet
String servletNameMapping = null;
do
{
elem = (XmlTag)parser.nextTag();
if (elem.isOpen())
parser.setPositionMarker();
else if (elem.isClose() && elem.getName().equals("servlet-name"))
servletNameMapping = parser.getInputFromPositionMarker(elem.getPos())
.toString();
}
while (!servletName.equals(servletNameMapping));
// and the urlPattern
do
{
elem = (XmlTag)parser.nextTag();
if (elem.isOpen())
parser.setPositionMarker();
else if (elem.isClose() && elem.getName().equals("url-pattern"))
urlPattern = parser.getInputFromPositionMarker(elem.getPos()).toString();
}
while (urlPattern == null);
// all it is found
break;
}
if (urlPattern == null)
throw new ServletException("Error searching for cometd Servlet");
// Check for leading '/' and trailing '/*'.
if (!urlPattern.startsWith("/") || !urlPattern.endsWith("/*"))
throw new ServletException(
"Url pattern for cometd should start with / and finish with /*");
// Strip trailing '/*'.
return servletContext.getContextPath() +
urlPattern.substring(0, urlPattern.length() - 2);
}
catch (final Exception ex)
{
final String path = servletContext.getContextPath() + "/cometd";
LOG.warn("Error finding filter cometd servlet in web.xml using default path " + path,
ex);
return path;
}
}
private final String _cometdChannelId;
private final String _cometdChannelIdWithoutSlash;
private final Map _handlers = new HashMap(
2);
/**
* Construct a cometd Behavior
*/
CometdPushBehavior()
{
_cometdChannelIdWithoutSlash = UUID.randomUUID().toString().replaceAll("-", "");
_cometdChannelId = "/" + _cometdChannelIdWithoutSlash;
}
/**
* @return JavaScript string containing the client side logic when a new event comes into the
* channel.
*/
private String _renderEventHandlerScript()
{
final Map map = new HashMap();
map.put("COMETD_CHANNEL_ID", _cometdChannelIdWithoutSlash);
map.put("CALLBACK_URL", getCallbackUrl().toString());
return TEMPLATE_EVENT_HANDLER.asString(map);
}
/**
* Javascript allowing cometd to be initialized on commetd
*
* @return javascript to initialize cometd on client side
*/
private String _renderInitScript()
{
final Map params = new HashMap();
final String configurationType = Application.get().getConfigurationType();
if (configurationType.equalsIgnoreCase(Application.DEVELOPMENT))
params.put("logLevel", "info");
else
params.put("logLevel", "error");
params.put("cometdServletPath", getCometdServletPath());
return TEMPLATE_INIT.asString(params);
}
/**
* @return JavaScript to subscribe to a cometd channel and handle cometd events
*/
private String _renderSubscribeScript()
{
final Map params = new HashMap();
params.put("COMETD_CHANNEL_ID", _cometdChannelIdWithoutSlash);
return TEMPLATE_SUBSCRIBE.asString(params);
}
CometdPushNode addNode(
final IPushEventHandler pushEventHandler)
{
final CometdPushNode node = new CometdPushNode(_cometdChannelId);
_handlers.put(node, pushEventHandler);
return node;
}
/**
* get the channel where this behavior will wait for event
*
* @return channelId channel where this behavior will wait for event
*/
public String getCometdChannelId()
{
return _cometdChannelId;
}
/**
* Returns the behaviour's cometd servlet path.
*
* Uses the {@link #DEFAULT_COMETD_PATH} provided by {@link #guessCometdServletPath()}. Override
* if you have an unusual setup.
*
* @return the behaviour's cometd servlet path.
*/
protected String getCometdServletPath()
{
return DEFAULT_COMETD_PATH;
}
int removeNode(final IPushNode node)
{
_handlers.remove(node);
return _handlers.size();
}
/**
* {@inheritDoc}
*/
@Override
public void renderHead(final IHeaderResponse response)
{
super.renderHead(response);
response.renderJavascriptReference(COMETD);
// Add all extension...
response.renderJavascriptReference(COMETD_ACK);
response.renderJavascriptReference(COMETD_RELOAD);
response.renderJavascriptReference(COMETD_TIMESTAMP);
response.renderJavascriptReference(COMETD_TIMESYNC);
response.renderJavascript(_renderInitScript(), "cometd-push-initialization");
response.renderJavascript(_renderEventHandlerScript(), null);
response.renderJavascript(_renderSubscribeScript(), null);
}
/**
* {@inheritDoc}
*/
@Override
protected void respond(final AjaxRequestTarget target)
{
final CometdPushService pushService = CometdPushService.get();
// retrieve all collected events and process them
for (final Entry entry : _handlers.entrySet())
{
final CometdPushNode node = entry.getKey();
for (final Iterator> it = pushService.pollEvents(node)
.iterator(); it.hasNext();)
{
final CometdPushEventContext ctx = it.next();
try
{
entry.getValue().onEvent(target, ctx.getEvent(), node, ctx);
}
catch (final RuntimeException ex)
{
LOG.error("Failed while processing event", ex);
}
}
}
}
}