smack 监听不同packet机制

之前做即时通讯，扒了smack源码来参考。说下其中解包后进行通知的机制。

Filter类：accept(Packet packet)函数，传入packet在此函数中进行对比判断，返回true 则通过此filter认证。实现PacketFilter接口即可。

public interface PacketFilter {

    /**
     * Tests whether or not the specified packet should pass the filter.
     *
     * @param packet the packet to test.
     * @return true if and only if <tt>packet</tt> passes the filter.
     */
    public boolean accept(Packet packet);
}

ListenerWrapper类：packetListener对应了自己在应用中定义的Listener（实现PacketListener接口），当通过对应的packetFilter之后，则进行回掉;

/**
     * A wrapper class to associate a packet filter with a listener.
     */
    protected static class ListenerWrapper {

        private PacketListener packetListener;
        private PacketFilter packetFilter;

        /**
         * Create a class which associates a packet filter with a listener.
         * 
         * @param packetListener the packet listener.
         * @param packetFilter the associated filter or null if it listen for all packets.
         */
        public ListenerWrapper(PacketListener packetListener, PacketFilter packetFilter) {
            this.packetListener = packetListener;
            this.packetFilter = packetFilter;
        }

        /**
         * Notify and process the packet listener if the filter matches the packet.
         * 
         * @param packet the packet which was sent or received.
         */
        public void notifyListener(Packet packet) {
            if (packetFilter == null || packetFilter.accept(packet)) {
                packetListener.processPacket(packet);
            }
        }
    }

public interface PacketListener {

    /**
     * Process the next packet sent to this packet listener.<p>
     *
     * A single thread is responsible for invoking all listeners, so
     * it's very important that implementations of this method not block
     * for any extended period of time.
     *
     * @param packet the packet to process.
     */
    public void processPacket(Packet packet);

}

接下来就是分包了，PacketReader中listenerExecutor.submit(new ListenerNotification(packet));在ListenerNotification线程里面进行判断，关键代码如下，写在run里面

for (ListenerWrapper listenerWrapper : connection.recvListeners.values()) {
                listenerWrapper.notifyListener(packet);
            }

通过迭代出ListenerWrapper调用notifyListener函数，查找通过验证的filter然后相对应是哪个listener就进行通知。