XMPP协议学习笔记五（Openfire消息处理流程）

wintelsui 2013-09-29

展开全文

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

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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()

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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。

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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();
}