CometD publish a message back to a client

问题:

I am having a problem in sending back a message to a client. Below is my code

JavaScript

dojox.cometd.publish('/service/getservice', {
                        userid : _USERID,

                    });
dojox.cometd.subscribe('/service/getservice', function(
            message) {
        alert("abc");
        alert(message.data.test);
    });

Configuration Servlet

bayeux.createIfAbsent("/service/getservice", new ConfigurableServerChannel.Initializer() {

        @Override
        public void configureChannel(ConfigurableServerChannel channel) {
            channel.setPersistent(true);
            GetListener channelListner = new GetListener();
            channel.addListener(channelListner);
        }
    });

GetListener class

public class GetListener implements MessageListener {
 public boolean onMessage(ServerSession ss, ServerChannel sc) {
      SomeClassFunction fun = new SomeClassFunction;
}
}

SomeClassFunction

class SomeClassFunction(){

}

here i am creating a boolean variable boolean success; if it is true send a message to client which is in javascript. how to send a message back to client. i have tried this line also.

      remote.deliver(getServerSession(), "/service/getservice",
                    message, null);

but it is giving me an error on remote object and getServerSession method.

回答1:

In order to reach your goal, you don't need to implement listeners nor to configure channels. You may need to add some configuration at a later stage, for example in order to add authorizers.

This is the code for the ConfigurationServlet, taken from this link:

public class ConfigurationServlet extends GenericServlet
{
    public void init() throws ServletException
    {
        // Grab the Bayeux object
        BayeuxServer bayeux = (BayeuxServer)getServletContext().getAttribute(BayeuxServer.ATTRIBUTE);
        new EchoService(bayeux);
        // Create other services here

        // This is also the place where you can configure the Bayeux object
        // by adding extensions or specifying a SecurityPolicy
    }

    public void service(ServletRequest request, ServletResponse response) throws ServletException, IOException
    {
        throw new ServletException();
    }
}

This is the code for EchoService class, taken fro this link:

public class EchoService extends AbstractService
{
    public EchoService(BayeuxServer bayeuxServer)
    {
        super(bayeuxServer, "echo");
        addService("/echo", "processEcho");
    }

    public void processEcho(ServerSession remote, Map<String, Object> data)
    {
        // if you want to echo the message to the client that sent the message
        remote.deliver(getServerSession(), "/echo", data, null);

        // if you want to send the message to all the subscribers of the "/myChannel" channel
        getBayeux().createIfAbsent("/myChannel");
        getBayeux().getChannel("/myChannel").publish(getServerSession(), data, null);
    }
}