CometD 将数据发布到频道的问题答案

【问题标题】：CometD Issues with Publishing Data to a ChannelCometD 将数据发布到频道的问题
【发布时间】：2014-01-02 11:59:36
【问题描述】：

我是 cometd 的新手，我计划向服务器发送一条消息并使用 cometd 在我的浏览器中获取消息如果我发送一条消息，它会成功发送到服务器，但无法在浏览器中获取它

 private void testService() {
String channelName = "/service/out";


log.info("Channel Name = " + channelName);
        log.info("bayeuxServer : " + (bayeuxServer == null ? "Is Null" : "Is Not Null"));



System.out.println("CHANNELS : " + bayeuxServer.getChannels().toString());
        System.out.println("Subscribers on /service/in = "+bayeuxServer.getChannel("/service/in").getSubscribers().toString());
        System.out.println("Subscribers on /service/out = "+bayeuxServer.getChannel("/service/out").getSubscribers().toString());

// convert to cometd format
        Map<String, Object> data = new HashMap<String, Object>(4);
        data.put("serverMsg", getDetails());
ServerChannel channel = bayeuxServer.getChannel(channelName);
subscribers = channel.getSubscribers().size();
        log.info("Subscribers = " + subscribers);
        log.info("channel = " + channel);
channel.publish(sender, data, null);


System.out.println("Session subscriptions :" + sender.getServerSession().getSubscriptions());
        System.out.println("Listeners on /service/out = "+bayeuxServer.getChannel("/service/out").getListeners().toString());
        System.out.println("Subscribers on /service/out = "+bayeuxServer.getChannel("/service/out").getSubscribers().toString());

}

但是这个不行

  @Subscription("/service/out")
    public void echo(Message message)
    {
        System.out.println("Echo service published " + message);
    }

日志：

7:48:18,775 INFO  ClientHelloService [] Bayeux server =org.cometd.server.BayeuxServerImpl@1436088
17:48:18,775 INFO  ClientHelloService [] Message = Hello world
17:48:18,775 INFO  ClientHelloService [] remote Client Id = 3renjdwk25ercglzli36tudpl
17:48:18,776 INFO  ClientHelloService [] Local session = L:_21w17u5f3mvvluvp71c27yaqvt
17:48:18,776 INFO  ClientHelloService [] session = 3renjdwk25ercglzli36tudpl - last connect 1 ms ago
17:48:18,776 INFO  ClientHelloService [] Channel Name = /service/out
17:48:18,776 INFO  ClientHelloService [] bayeuxServer : Is Not Null
CHANNELS : [/service/out, /meta/subscribe, /service, /service/*, /meta, /meta/handshake, /meta/disconnect, /service/in, /meta/connect, /meta/unsubscribe]
Subscribers on /service/in = []
Subscribers on /service/out = []
17:48:18,777 INFO  ClientHelloService [] msg = Hello world
17:48:18,777 INFO  ClientHelloService [] Subscribers = 0
17:48:18,777 INFO  ClientHelloService [] channel = /service/out
17:48:18,777 DEBUG 21192840 [] <  {data={serverMsg=Hello world}, channel=/service/out}
17:48:18,777 INFO  ClientHelloService [] publish the channel
Session subscriptions :[]
Listeners on /service/out = []
Subscribers on /service/out = []

应用程序.js

var sendChannel = '/service/in';            // Message from jsp
var receiveChannel = '/service/*';       // Message from server
/*var cometdServerURL = 'http://127.0.0.1:8080/cometd';*/

require(['dojox/cometd', 'dojo/dom', 'dojo/domReady!'], function(cometd, dom)
{       //  // configuration object
  //  cometd.websocketEnabled = true;
   // Open connection to CometD server
    cometd.configure({
        url: location.protocol + '//' + location.host + config.contextPath + '/cometd',
        logLevel: 'debug'
    });

cometd.addListener('/meta/*', function(message)
    {
        if (message.successful)
        {
            dom.byId('status').innerHTML += '<div>CometD handshake successful</div>';

            cometd.subscribe(receiveChannel, function(message) {
                dom.byId('results').innerHTML +=' Message  from server  ' + message.data;
                dom.byId('results').innerHTML +=' Subscription to ' + receiveChannel;
            });
        }
        else if(_connectionBroken()){
            dom.byId('status').innerHTML += '<div>CometD Connection Broken</div>';
        }
        else
        {
            dom.byId('status').innerHTML += '<div>CometD handshake failed</div>';
        }
    });
dom.byId('greeter').onclick = function()
    {
        var text = dom.byId('msg').value;
        cometd.publish(sendChannel, 'Hello world');
        dom.byId('msg').value = "" ;
        dom.byId('results').innerHTML +='Message send to server' ;
    };
    cometd.handshake();
});

【问题讨论】：

标签： push-notification cometd ajax-polling bayeux

【解决方案1】：

您的代码中有几个错误，如下所述。

首先，您不希望在您的 javascript 中向/meta/* 添加一个侦听器来处理if (message.successful) 分支中的订阅。该分支将针对任何元消息响应执行，例如也针对订阅响应（通过/meta/subscribe 发送），在无意中多次执行代码。

将侦听器更改为侦听/meta/handshake 频道并在该侦听器中执行订阅。

同样，您希望在 /meta/connect 侦听器中执行 if (_connectionBroken()) 分支。

请参考primer 来构建您的应用程序的适当骨架。另外，请关注tutorials，以更好地了解听众的角色。

其次，不建议您从客户端订阅服务频道。阅读 CometD concepts 以了解服务频道和广播频道之间的区别，以及添加侦听器和订阅之间的 difference。

第三，当您有服务通道时，publish() 是本地活动，因此不会将消息传递给远程客户端。如果您真的想使用服务通道，在这种情况下使用的正确 API 是 ServerSession.deliver(...)。

最后，tutorials 涵盖了您的用例，因此我建议您遵循这些，您的应用程序将正常运行。

希望有所帮助。

【讨论】：

你能告诉我如何发布频道
session.deliver(sender, channel.getId(), data, null);这也没有发布
欢迎您加入CometD mailing list 并在那里提供更多详细信息（例如代码和调试日志）。单行评论描述很难提供帮助，但请相信我 session.deliver(...) 工作正常。

【解决方案2】：

var sendChannel = '/service/in';            // Message from jsp
var receiveChannel = '/service/out';       // Message from server
/*var cometdServerURL = 'http://127.0.0.1:8080/cometd';*/

require(['dojox/cometd', 'dojo/dom', 'dojo/domReady!','dojo/_base/unload'], function(cometd, dom)
{       //  // configuration object

   // Open connection to CometD server
    cometd.configure({
        url: location.protocol + '//' + location.host + config.contextPath + '/cometd',
        logLevel: 'debug'
    });
   cometd.addListener('/meta/connect', function(message) {
        var wasConnected;
        if(cometd.isDisconnected()) {
            dom.byId('status').innerHTML +=' Disconnected from the server  = ' +  message;
        }  else{
           /* dom.byId('status').innerHTML +=' Disconnected from the server  = ' +  message.data;*/
        }
    });

 // listener for handshake
    cometd.addListener('/meta/handshake', function(message)
    {
        if (message.successful)
        {
            dom.byId('status').innerHTML += '<div>CometD handshake successful</div>';
            cometd.batch(function()
            {
            cometd.subscribe(receiveChannel, function(message) {
                dom.byId('results').innerHTML +=' Message  from server  ' + message.data;
                dom.byId('results').innerHTML +=' Subscription to ' + receiveChannel;
            });
               // cometd.publish('/service/in', { name: 'World' });
            });
        }
        else if(_connectionBroken()){
            dom.byId('status').innerHTML += '<div>CometD Connection Broken</div>';
        }
        else
        {
            dom.byId('status').innerHTML += '<div>CometD handshake failed</div>';
        }
    });

    dom.byId('greeter').onclick = function()
    {
        var text = dom.byId('msg').value;
        cometd.publish(sendChannel, 'Hello world');
        dom.byId('msg').value = "" ;
        dom.byId('results').innerHTML +='Message send to server' ;
    };
    cometd.handshake();

  });

现在也无法发布到频道

@Service
public class ClientHelloService {

    static Logger log = Logger.getLogger(
            ClientHelloService.class.getName());
    String details;
    @Inject
    private BayeuxServer bayeuxServer;
    @Session
    private LocalSession sender;
    @Session
    private ClientSession bayeuxClient;
    @Session
    ServerSession session;
    int subscribers;
       // represent callback
    @Listener("/service/in")
    public void processClientHello(ServerSession session, ServerMessage message)
    {
        log.info("Bayeux server =" + bayeuxServer);
        log.info("Message = " + message.getData());
        log.info("remote Client Id = " + session.getId());
        log.info("Local session = " + sender);
        log.info("session = " + getSession());
       // log.info("sender = " + sender);
        details = (String) message.getData();
       // session.deliver(sender,"/service/out",getDetails() , null);
        testService();
    }

    private void testService() {
        // Create the channel name  using the symbol

        String channelName = "/service/out";
        log.info("Channel Name = " + channelName);
        log.info("bayeuxServer : " + (bayeuxServer == null ? "Is Null" : "Is Not Null"));
        // Initialize the channel, making it persistant
        // new sendChannel
        bayeuxServer.createIfAbsent(channelName, new ConfigurableServerChannel.Initializer() {
            public void configureChannel(ConfigurableServerChannel channel) {
                log.info("Configurable channel " + channel);
                //  channel exists even if it has no subscribers
                channel.setPersistent(true);
                channel.setLazy(true);
            }
        });
        System.out.println("CHANNELS : " + bayeuxServer.getChannels().toString());
        System.out.println("Subscribers on /service/out = "+bayeuxServer.getChannel("/service/out").getSubscribers().toString());

        // convert to cometd format
        Map<String, Object> data = new HashMap<String, Object>(4);
        data.put("serverMsg", getDetails());
        log.info("msg = " + data.get("serverMsg"));

        // Publish the channel  to all
        ServerChannel channel = bayeuxServer.getChannel(channelName);
        subscribers = channel.getSubscribers().size();
        log.info("Subscribers = " + subscribers);
        log.info("channel = " + channel);
        // publish the message
        try {
            channel.publish(getSession(), data, null);
            log.info("publish the channel");
        }
        catch (Exception e){
            System.out.println(" Exception = " + e);
        }
        System.out.println("Session subscriptions :" + sender.getServerSession().getSubscriptions());
        System.out.println("Listeners on /service/out = "+bayeuxServer.getChannel("/service/out").getListeners().toString());
        System.out.println("Subscribers on /service/out = "+bayeuxServer.getChannel("/service/out").getSubscribers().toString());

        publishData(data);
    }

    public ServerSession getSession() {
        return session;
    }

    public void setSession(ServerSession session) {
        this.session = session;
    }

    private void publishData(Map<String, Object> data) {
        System.out.println("Published data = " + data);
    }
    /* @org.cometd.annotation.Subscription("/service/out")*/
   @Subscription("/service/out")
    public void echo(Message message)
    {
        System.out.println("Echo service published " + message);
    }

    public String getDetails() {
        return details;
    }

    public void setDetails(String details) {
        this.details = details;
    }
}

【讨论】：