org.cometd.server.BayeuxService Maven / Gradle / Ivy
// ========================================================================
// Copyright 2008 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// 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.cometd.server;
import java.lang.reflect.Method;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import org.cometd.Bayeux;
import org.cometd.Channel;
import org.cometd.Client;
import org.cometd.Listener;
import org.cometd.Message;
import org.cometd.MessageListener;
import org.eclipse.jetty.util.component.LifeCycle;
import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.thread.QueuedThreadPool;
import org.eclipse.jetty.util.thread.ThreadPool;
/* ------------------------------------------------------------ */
/**
* Abstract Bayeux Service class. This is a base class to assist with the
* creation of server side @ link Bayeux} clients that provide services to
* remote Bayeux clients. The class provides a Bayeux {@link Client} and
* {@link Listener} together with convenience methods to map subscriptions to
* methods on the derived class and to send responses to those methods.
*
*
* If a {@link #set_threadPool(ThreadPool)} is set, then messages are handled in
* their own threads. This is desirable if the handling of a message can take
* considerable time and it is desired not to hold up the delivering thread
* (typically a HTTP request handling thread).
*
*
* If the BayeuxService is constructed asynchronously (the default), then
* messages are delivered unsynchronized and multiple simultaneous calls to
* handling methods may occur.
*
*
* If the BayeuxService is constructed as a synchronous service, then message
* delivery is synchronized on the internal {@link Client} instances used and
* only a single call will be made to the handler method (unless a thread pool
* is used).
*
* @see MessageListener
* @author gregw
*
*/
public abstract class BayeuxService
{
private String _name;
private Bayeux _bayeux;
private Client _client;
private Map _methods=new ConcurrentHashMap();
private ThreadPool _threadPool;
private MessageListener _listener;
private boolean _seeOwn=false;
/* ------------------------------------------------------------ */
/**
* Instantiate the service. Typically the derived constructor will call @
* #subscribe(String, String)} to map subscriptions to methods.
*
* @param bayeux
* The bayeux instance.
* @param name
* The name of the service (used as client ID prefix).
*/
public BayeuxService(Bayeux bayeux, String name)
{
this(bayeux,name,0,false);
}
/* ------------------------------------------------------------ */
/**
* Instantiate the service. Typically the derived constructor will call @
* #subscribe(String, String)} to map subscriptions to methods.
*
* @param bayeux
* The bayeux instance.
* @param name
* The name of the service (used as client ID prefix).
* @param maxThreads
* The size of a ThreadPool to create to handle messages.
*/
public BayeuxService(Bayeux bayeux, String name, int maxThreads)
{
this(bayeux,name,maxThreads,false);
}
/* ------------------------------------------------------------ */
/**
* Instantiate the service. Typically the derived constructor will call @
* #subscribe(String, String)} to map subscriptions to methods.
*
* @param bayeux
* The bayeux instance.
* @param name
* The name of the service (used as client ID prefix).
* @param maxThreads
* The size of a ThreadPool to create to handle messages.
* @param synchronous
* True if message delivery will be synchronized on the client.
*/
public BayeuxService(Bayeux bayeux, String name, int maxThreads, boolean synchronous)
{
if (maxThreads > 0)
setThreadPool(new QueuedThreadPool(maxThreads));
_name=name;
_bayeux=bayeux;
_client=_bayeux.newClient(name);
_listener=(synchronous)?new SyncListen():new AsyncListen();
_client.addListener(_listener);
}
/* ------------------------------------------------------------ */
public Bayeux getBayeux()
{
return _bayeux;
}
/* ------------------------------------------------------------ */
public Client getClient()
{
return _client;
}
/* ------------------------------------------------------------ */
public ThreadPool getThreadPool()
{
return _threadPool;
}
/* ------------------------------------------------------------ */
/**
* Set the threadpool. If the {@link ThreadPool} is a {@link LifeCycle},
* then it is started by this method.
*
* @param pool
*/
public void setThreadPool(ThreadPool pool)
{
try
{
if (pool instanceof LifeCycle)
if (!((LifeCycle)pool).isStarted())
((LifeCycle)pool).start();
}
catch(Exception e)
{
throw new IllegalStateException(e);
}
_threadPool=pool;
}
/* ------------------------------------------------------------ */
public boolean isSeeOwnPublishes()
{
return _seeOwn;
}
/* ------------------------------------------------------------ */
public void setSeeOwnPublishes(boolean own)
{
_seeOwn=own;
}
/* ------------------------------------------------------------ */
/**
* Subscribe to a channel. Subscribe to channel and map a method to handle
* received messages. The method must have a unique name and one of the
* following signatures:
*
* myMethod(Client fromClient,Object data)myMethod(Client fromClient,Object data,String id)-
*
myMethod(Client fromClient,String channel,Object data,String id)
*
*
*
* The data parameter can be typed if the type of the data object published
* by the client is known (typically Map). If the type of the
* data parameter is {@link Message} then the message object itself is
* passed rather than just the data.
*
* Typically a service will subscribe to a channel in the "/service/**"
* space which is not a broadcast channel. Messages published to these
* channels are only delivered to server side clients like this service.
*
*
* Any object returned by a mapped subscription method is delivered to the
* calling client and not broadcast. If the method returns void or null,
* then no response is sent. A mapped subscription method may also call
* {@link #send(Client, String, Object, String)} to deliver a response
* message(s) to different clients and/or channels. It may also publish
* methods via the normal {@link Bayeux} API.
*
*
*
* @param channelId
* The channel to subscribe to
* @param methodName
* The name of the method on this object to call when messages
* are recieved.
*/
protected void subscribe(String channelId, String methodName)
{
Method method=null;
Class c=this.getClass();
while(c != null && c != Object.class)
{
Method[] methods=c.getDeclaredMethods();
for (int i=methods.length; i-- > 0;)
{
if (methodName.equals(methods[i].getName()))
{
if (method != null)
throw new IllegalArgumentException("Multiple methods called '" + methodName + "'");
method=methods[i];
}
}
c=c.getSuperclass();
}
if (method == null)
throw new NoSuchMethodError(methodName);
int params=method.getParameterTypes().length;
if (params < 2 || params > 4)
throw new IllegalArgumentException("Method '" + methodName + "' does not have 2or3 parameters");
if (!Client.class.isAssignableFrom(method.getParameterTypes()[0]))
throw new IllegalArgumentException("Method '" + methodName + "' does not have Client as first parameter");
Channel channel=_bayeux.getChannel(channelId,true);
if (((ChannelImpl)channel).getChannelId().isWild())
{
final Method m=method;
Client wild_client=_bayeux.newClient(_name + "-wild");
wild_client.addListener(_listener instanceof MessageListener.Asynchronous?new AsyncWildListen(wild_client,m):new SyncWildListen(wild_client,m));
channel.subscribe(wild_client);
}
else
{
_methods.put(channelId,method);
channel.subscribe(_client);
}
}
/* ------------------------------------------------------------ */
/**
* Send data to a individual client. The data passed is sent to the client
* as the "data" member of a message with the given channel and id. The
* message is not published on the channel and is thus not broadcast to all
* channel subscribers. However to the target client, the message appears as
* if it was broadcast.
*
* Typcially this method is only required if a service method sends
* response(s) to channels other than the subscribed channel. If the
* response is to be sent to the subscribed channel, then the data can
* simply be returned from the subscription method.
*
* @param toClient
* The target client
* @param onChannel
* The channel the message is for
* @param data
* The data of the message
* @param id
* The id of the message (or null for a random id).
*/
protected void send(Client toClient, String onChannel, Object data, String id)
{
toClient.deliver(getClient(),onChannel,data,id);
}
/* ------------------------------------------------------------ */
/**
* Handle Exception. This method is called when a mapped subscription method
* throws and exception while handling a message.
*
* @param fromClient
* @param toClient
* @param msg
* @param th
*/
protected void exception(Client fromClient, Client toClient, Map msg, Throwable th)
{
System.err.println(msg);
th.printStackTrace();
}
/* ------------------------------------------------------------ */
private void invoke(final Method method, final Client fromClient, final Client toClient, final Message msg)
{
if (_threadPool == null)
doInvoke(method,fromClient,toClient,msg);
else
{
_threadPool.dispatch(new Runnable()
{
public void run()
{
try
{
((MessageImpl)msg).incRef();
doInvoke(method,fromClient,toClient,msg);
}
finally
{
((MessageImpl)msg).decRef();
}
}
});
}
}
/* ------------------------------------------------------------ */
private void doInvoke(Method method, Client fromClient, Client toClient, Message msg)
{
String channel=(String)msg.get(Bayeux.CHANNEL_FIELD);
Object data=msg.get(Bayeux.DATA_FIELD);
String id=msg.getId();
if (method != null)
{
try
{
Class[] args=method.getParameterTypes();
Object arg=Message.class.isAssignableFrom(args[1])?msg:data;
Object reply=null;
switch(method.getParameterTypes().length)
{
case 2:
reply=method.invoke(this,fromClient,arg);
break;
case 3:
reply=method.invoke(this,fromClient,arg,id);
break;
case 4:
reply=method.invoke(this,fromClient,channel,arg,id);
break;
}
if (reply != null)
send(fromClient,channel,reply,id);
}
catch(Exception e)
{
Log.debug("method",method);
exception(fromClient,toClient,msg,e);
}
catch(Error e)
{
Log.debug("method",method);
exception(fromClient,toClient,msg,e);
}
}
}
/* ------------------------------------------------------------ */
/* ------------------------------------------------------------ */
private class AsyncListen implements MessageListener, MessageListener.Asynchronous
{
public void deliver(Client fromClient, Client toClient, Message msg)
{
if (!_seeOwn && fromClient == getClient())
return;
String channel=(String)msg.get(Bayeux.CHANNEL_FIELD);
Method method=_methods.get(channel);
invoke(method,fromClient,toClient,msg);
}
}
/* ------------------------------------------------------------ */
/* ------------------------------------------------------------ */
private class SyncListen implements MessageListener, MessageListener.Synchronous
{
public void deliver(Client fromClient, Client toClient, Message msg)
{
if (!_seeOwn && fromClient == getClient())
return;
String channel=(String)msg.get(Bayeux.CHANNEL_FIELD);
Method method=_methods.get(channel);
invoke(method,fromClient,toClient,msg);
}
}
/* ------------------------------------------------------------ */
/* ------------------------------------------------------------ */
private class SyncWildListen implements MessageListener, MessageListener.Synchronous
{
Client _client;
Method _method;
public SyncWildListen(Client client, Method method)
{
_client=client;
_method=method;
}
public void deliver(Client fromClient, Client toClient, Message msg)
{
if (!_seeOwn && (fromClient == _client || fromClient == getClient()))
return;
invoke(_method,fromClient,toClient,msg);
}
};
/* ------------------------------------------------------------ */
/* ------------------------------------------------------------ */
private class AsyncWildListen implements MessageListener, MessageListener.Asynchronous
{
Client _client;
Method _method;
public AsyncWildListen(Client client, Method method)
{
_client=client;
_method=method;
}
public void deliver(Client fromClient, Client toClient, Message msg)
{
if (!_seeOwn && (fromClient == _client || fromClient == getClient()))
return;
invoke(_method,fromClient,toClient,msg);
}
};
}