在 (一)androidpn-server tomcat版源码解析之--项目启动这篇中，已经描述了整个推送服务器的启动过程，并且把握到了消息的入口即XmppIoHandler这个类，今天我将继续往下分析下面的核心代码，主要分为3大块，链接创建，消息的发送，链接关闭。

先贴一段XmppIoHandler的部分代码

/**
     * Invoked from an I/O processor thread when a new connection has been created.
     */
    public void sessionCreated(IoSession session) throws Exception {
        log.debug("sessionCreated()...");
        session.getConfig().setBothIdleTime(IDLE_TIME);;
    }

    /**
     * Invoked when a connection has been opened.
     */
    public void sessionOpened(IoSession session) throws Exception {
        log.debug("sessionOpened()...");
        log.debug("remoteAddress=" + session.getRemoteAddress());
        // Create a new XML parser
        XMLLightweightParser parser = new XMLLightweightParser("UTF-8");
        session.setAttribute(XML_PARSER, parser);
        // Create a new connection
        Connection connection = new Connection(session);
        session.setAttribute(CONNECTION, connection);
        session.setAttribute(STANZA_HANDLER, new StanzaHandler(serverName,
                connection));
    }

    /**
     * Invoked when a connection is closed.
     */
    public void sessionClosed(IoSession session) throws Exception {
        log.debug("sessionClosed()...");
        Connection connection = (Connection) session.getAttribute(CONNECTION);
        connection.close();
    }

    /**
     * Invoked with the related IdleStatus when a connection becomes idle.
     */
    public void sessionIdle(IoSession session, IdleStatus status)
            throws Exception {
        log.debug("sessionIdle()...");
        Connection connection = (Connection) session.getAttribute(CONNECTION);
        if (log.isDebugEnabled()) {
            log.debug("Closing connection that has been idle: " + connection);
        }
        connection.close();
    }

    /**
     * Invoked when any exception is thrown.
     */
    public void exceptionCaught(IoSession session, Throwable cause)
            throws Exception {
        log.debug("exceptionCaught()...");
        log.error(cause);
    }

    /**
     * Invoked when a message is received.
     */
    public void messageReceived(IoSession session, Object message)
            throws Exception {
        log.debug("messageReceived()...");
        log.debug("RCVD: " + message);

        // Get the stanza handler
        StanzaHandler handler = (StanzaHandler) session
                .getAttribute(STANZA_HANDLER);

        // Get the XMPP packet parser
        int hashCode = Thread.currentThread().hashCode();
        XMPPPacketReader parser = parsers.get(hashCode);
        if (parser == null) {
            parser = new XMPPPacketReader();
            parser.setXPPFactory(factory);
            parsers.put(hashCode, parser);
        }

        // The stanza handler processes the message
        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();
        }
    }

    /**
     * Invoked when a message written by IoSession.write(Object) is sent out.
     */
    public void messageSent(IoSession session, Object message) throws Exception {
        log.debug("messageSent()...");
    }

•  链接创建

androidpn-server的消息处理步奏为： sessionCreated->sessionOpened->Router->handle

对应的处理类为：XmppIoHandler- >StanzaHandler->PacketRouterIQAuthHandler.java->IQHandler.java

                                                                                                                            IQRegisterHandler.java

                                                                                                                            IQRosterHandler.java

                                                                                                                            PresenceUpdateHandler.java

androidpn是以xmpp为协议的，要看懂以下的处理步奏也就必须补充点xmpp的一个相关知识

xmpp的三种消息类型:

message：message是一种基本推送消息方法，它不要求响应。

presence：presence用来表明用户的状态，如：online、away、dnd(请勿打扰)等

iq：一种请求／响应机制，从一个实体从发送请求，另外一个实体接受请求，并进行响应。

XmppIoHandler.java->  sessionCreated：

public void sessionCreated(IoSession session) throws Exception {
        log.debug("sessionCreated()...");
        session.getConfig().setBothIdleTime(IDLE_TIME);;
    }

 client的请求第一次到达时候为session设置了一个idletime

XmppIoHandler.java-> sessionOpened

public void sessionOpened(IoSession session) throws Exception {
        log.debug("sessionOpened()...");
        log.debug("remoteAddress=" + session.getRemoteAddress());
        // Create a new XML parser
        XMLLightweightParser parser = new XMLLightweightParser("UTF-8");
        session.setAttribute(XML_PARSER, parser);
        // Create a new connection
        Connection connection = new Connection(session);
        session.setAttribute(CONNECTION, connection);
        session.setAttribute(STANZA_HANDLER, new StanzaHandler(serverName,
                connection));
    }

 初始化了xml解析器，并且创建了StanzaHandler实例，StanzaHandler这个类时后续处理的关键

StanzaHandler.java-> StanzaHandler

/**
     * Constructor.
     * 
     * @param serverName the server name
     * @param connection the connection
     */
    public StanzaHandler(String serverName, Connection connection) {
        this.serverName = serverName;
        this.connection = connection;
        this.router = new PacketRouter();//该构造中初始化了三个router实现,分别是 MessageRouter,PresenceRouter,IQRouter,分别处理xmpp的三种消息类型
        notificationService = ServiceLocator.getNotificationService();
        notificationManager = new NotificationManager();
    }

 XmppIoHandler.java-> messageReceived

public void messageReceived(IoSession session, Object message)
            throws Exception {
        log.debug("messageReceived()...");
        log.debug("RCVD: " + message);

        // Get the stanza handler
        StanzaHandler handler = (StanzaHandler) session
                .getAttribute(STANZA_HANDLER);

        // Get the XMPP packet parser
        int hashCode = Thread.currentThread().hashCode();
        XMPPPacketReader parser = parsers.get(hashCode);
        if (parser == null) {
            parser = new XMPPPacketReader();
            parser.setXPPFactory(factory);
            parsers.put(hashCode, parser);
        }

        // The stanza handler processes the message
        try {
            handler.process((String) message, parser);//###这个方法中，程序会根据xmpp的xml头来判断消息类型，并且传递到对应的Router处理类
        } catch (Exception e) {
            log.error(
                    "Closing connection due to error while processing message: "
                            + message, e);
            Connection connection = (Connection) session
                    .getAttribute(CONNECTION);
            connection.close();
        }
    }

 因为当前做的需求是消息推送，而MessageRouter实用在IM这种对话场合，所以MessageRouter并没有实现处理PresenceRouter和IQRouter都有对应的功能实现。

IQRoute.java -> IQRouter

public IQRouter() {
        sessionManager = SessionManager.getInstance();
        iqHandlers.add(new IQAuthHandler());
        iqHandlers.add(new IQRegisterHandler());
        iqHandlers.add(new IQRosterHandler());
        notificationService = ServiceLocator.getNotificationService();
    }

 构造中又实现了3和handler，用户建立好链接后又会对用户进行IQAuthHandler（鉴权），IQRegisterHandler（解析用户携带参数，往数据库中插入用户信息，将链接保存在sessionManager中），IQRosterHandler（没进行什么操作）

• 消息的发送

以广播消息为例

SessionManager.java

/**
     * Returns a list that contains all authenticated client sessions.
     * 
     * @return a list that contains all client sessions
     */
    public Collection<ClientSession> getSessions() {
        return clientSessions.values();
    }

 获得链接池中所有链接

Session.java

/**
     * Delivers the packet to the associated connection.
     * 
     * @param packet the packet to deliver
     */
    public void deliver(Packet packet) {
        if (connection != null && !connection.isClosed()) {
            connection.deliver(packet);
        }
    }

 Connection.java

/**
     * Delivers the packet to this connection (without checking the recipient).
     * 
     * @param packet the packet to deliver
     */
    public void deliver(Packet packet) {
        log.debug("SENT: " + packet.toXML());
        if (!isClosed()) {
            IoBuffer buffer = IoBuffer.allocate(4096);
            buffer.setAutoExpand(true);

            boolean errorDelivering = false;
            try {
                XMLWriter xmlSerializer = new XMLWriter(new IoBufferWriter(
                        buffer, (CharsetEncoder) encoder.get()),
                        new OutputFormat());
                xmlSerializer.write(packet.getElement());
                xmlSerializer.flush();
                buffer.flip();
                ioSession.write(buffer);//###通过mina的isSession对象传递
            } catch (Exception e) {
                log.debug("Connection: Error delivering packet" + "\n"
                        + this.toString(), e);
                errorDelivering = true;
            }
            if (errorDelivering) {
                close();
            } else {
                session.incrementServerPacketCount();
            }
        }
    }

 封装层次为isSession->Connection->Session

• 链接关闭

XmppIoHandler.java

/**
     * Invoked when a connection is closed.
     */
    public void sessionClosed(IoSession session) throws Exception {
        log.debug("sessionClosed()...");
        Connection connection = (Connection) session.getAttribute(CONNECTION);
        connection.close();
    }

 Connection.java

/**
     * Closes the session including associated socket connection,
     * notifing all listeners that the channel is shutting down.
     */
    public void close() {
        boolean closedSuccessfully = false;
        synchronized (this) {
            if (!isClosed()) {
                try {
                    deliverRawText("</stream:stream>", false);
                } catch (Exception e) {
                    // Ignore
                }
                if (session != null) {
                    session.setStatus(Session.STATUS_CLOSED);
                }
                ioSession.close(false);
                closed = true;
                closedSuccessfully = true;
            }
        }
        if (closedSuccessfully) {
            notifyCloseListeners();
        }
    }

 此处使用了观察者模式,首先传递了Xmpp的结束xml“</stream:stream>”，再关闭了mina最低层的ioSession，再通知观察者，也就是androidpn封装的ClientSession在内存中删除该会话。