XMPP协议学习笔记五（Openfire消息处理流程）

     XMPP协议作为一个IM，其核心在于消息的传递，在Openfire服务器对XMPP的实现中，消息被封装为Packet对象，因此Openfire服务器的核心代码是对客户端Packet对象的监听和处理流程，我们今天就来研究一下Openfire的消息包接受处理流程。

    

• 首先，Openfire服务器需要启动一个基于TCP/IP的监听服务，用以接收客户端传过来的XML流文件。这个过程在XMPPServer类的start()方法中进行，这个监听服务是以loadModule(ConnectionManagerImpl.class.getName())来加载，调用ConnectionManagerImpl类的createClientListeners()方法

    private void createClientListeners() {
        // Start clients plain socket unless it's been disabled.
        if (isClientListenerEnabled()) {
            // Create SocketAcceptor with correct number of processors
            socketAcceptor = buildSocketAcceptor();
            // Customize Executor that will be used by processors to process incoming stanzas
            ExecutorThreadModel threadModel = ExecutorThreadModel.getInstance("client");
            int eventThreads = JiveGlobals.getIntProperty("xmpp.client.processing.threads", 16);
            ThreadPoolExecutor eventExecutor = (ThreadPoolExecutor)threadModel.getExecutor();
            eventExecutor.setCorePoolSize(eventThreads + 1);
            eventExecutor.setMaximumPoolSize(eventThreads + 1);
            eventExecutor.setKeepAliveTime(60, TimeUnit.SECONDS);

            socketAcceptor.getDefaultConfig().setThreadModel(threadModel);
            // Add the XMPP codec filter
            socketAcceptor.getFilterChain().addFirst("xmpp", new ProtocolCodecFilter(new XMPPCodecFactory()));
            // Kill sessions whose outgoing queues keep growing and fail to send traffic
            socketAcceptor.getFilterChain().addAfter("xmpp", "outCap", new StalledSessionsFilter());
        }
    }

• 其中的socketAcceptor是在buildSocektAcceptor()方法中定义的，它是作为一个服务端的接收器，是mina框架为我们封装好的一个socketserver，在上面这个方法中，我们为socketAcceptor添加了一个过滤器，XMPPCodeFactory，这个类将过滤xmpp相关请求，加以处理，我们再看同一个类的另外一个方法startClientListener()

     private void startClientListeners(String localIPAddress) {
        // Start clients plain socket unless it's been disabled.
        if (isClientListenerEnabled()) {
            int port = getClientListenerPort();
            try {
                // Listen on a specific network interface if it has been set.
                String interfaceName = JiveGlobals.getXMLProperty("network.interface");
                InetAddress bindInterface = null;
                if (interfaceName != null) {
                    if (interfaceName.trim().length() > 0) {
                        bindInterface = InetAddress.getByName(interfaceName);
                    }
                }
                // Start accepting connections
                socketAcceptor
                        .bind(new InetSocketAddress(bindInterface, port), new ClientConnectionHandler(serverName));

                ports.add(new ServerPort(port, serverName, localIPAddress, false, null, ServerPort.Type.client));

                List<String> params = new ArrayList<String>();
                params.add(Integer.toString(port));
                Log.info(LocaleUtils.getLocalizedString("startup.plain", params));
            }
            catch (Exception e) {
                System.err.println("Error starting XMPP listener on port " + port + ": " +
                        e.getMessage());
                Log.error(LocaleUtils.getLocalizedString("admin.error.socket-setup"), e);
            }
        }
    }

• 其中的socketAcceptor.bind()方法启动了监听服务器，来监听所有发送到服务器5222端口的数据，并用ClientConnetionHandler类来处理，ClinetConnectionHandler继承于ConnectionHandler类，后者实现了mina的IoHandlerAdaptor接口，其中的messageReceived()方法是关键。

        public void messageReceived(IoSession session, Object message) throws Exception {
        // Get the stanza handler for this session
        StanzaHandler handler = (StanzaHandler) session.getAttribute(HANDLER);
        // Get the parser to use to process stanza. For optimization there is going
        // to be a parser for each running thread. Each Filter will be executed
        // by the Executor placed as the first Filter. So we can have a parser associated
        // to each Thread
        int hashCode = Thread.currentThread().hashCode();
        XMPPPacketReader parser = parsers.get(hashCode);
        if (parser == null) {
            parser = new XMPPPacketReader();
            parser.setXPPFactory(factory);
            parsers.put(hashCode, parser);
        }
        // Update counter of read btyes
        updateReadBytesCounter(session);
        //System.out.println("RCVD: " + message);
        // Let the stanza handler process the received stanza
        try {
            handler.process((String) message, parser);
        } catch (Exception e) {
            Log.error("Closing connection due to error while processing message: " + message, e);
            Connection connection = (Connection) session.getAttribute(CONNECTION);
            connection.close();
        }
    }

• 可以看到收到的信息交由StanzaHandler的process方法中进行XML解析并封装为packet对象，然后再进行下一步的处理，至此，从客户端到服务器端的packet传递结束。