Apache mina:IoHandler

在應用層,也就是我們的業務層需要處理我們的IoHandler對象。我們知道IoFilter 過濾鍊處理資料的輸入輸出。而實際的資料輸入輸出是在IoProcessor線程中觸發事件來通知

FilterChain 來觸發事件。但是IoHandler又是怎麼觸發觸發的呢？？？這裡要從FilterChain源代碼來擷取的。

在IoFilterChain的構造方法中,我們注意到HeadFilter,TailFilter 兩個類。第一個過濾鍊和最後一個過濾鍊。
public class DefaultIoFilterChain implements IoFilterChain
 {
    public static final AttributeKey SESSION_CREATED_FUTURE = new AttributeKey(DefaultIoFilterChain.class,
            "connectFuture");
    /** The associated session */
    private final AbstractIoSession session;

    /** The mapping between the filters and their associated name */
    private final Map<String, Entry> name2entry = new ConcurrentHashMap<String, Entry>();

    /** The chain head */
    private final EntryImpl head;

    /** The chain tail */
    private final EntryImpl tail;
    /**
     * Create a new default chain, associated with a session. It will only contain a
     * HeadFilter and a TailFilter.
     */
    public DefaultIoFilterChain(AbstractIoSession session) {
        if (session == null) {
            throw new IllegalArgumentException("session");
        }

        this.session = session;
        head = new EntryImpl(null, null, "head", new HeadFilter());
        tail = new EntryImpl(head, null, "tail", new TailFilter());
        head.nextEntry = tail;
    }
}
           

//在IoFilterChain中最後一個過濾鍊執行的操作
    private static class TailFilter extends IoFilterAdapter {
        @Override
        public void sessionCreated(NextFilter nextFilter, IoSession session) throws Exception {
            try {
            	//擷取與IoSession相關聯的IoHandler,并調用相應的事件。
                session.getHandler().sessionCreated(session);
            } finally {
                // Notify the related future.
                ConnectFuture future = (ConnectFuture) session.removeAttribute(SESSION_CREATED_FUTURE);

                if (future != null) {
                    future.setSession(session);
                }
            }
        }
        
        @Override
        public void sessionOpened(NextFilter nextFilter, IoSession session) throws Exception {
            session.getHandler().sessionOpened(session);
        }

        @Override
        public void sessionClosed(NextFilter nextFilter, IoSession session) throws Exception {
            AbstractIoSession s = (AbstractIoSession) session;

            try {
                s.getHandler().sessionClosed(session);
            } finally {
                try {
                    s.getWriteRequestQueue().dispose(session);
                } finally {
                    try {
                        s.getAttributeMap().dispose(session);
                    } finally {
                        try {
                            // Remove all filters.
                            session.getFilterChain().clear();
                        } finally {
                            if (s.getConfig().isUseReadOperation()) {
                                s.offerClosedReadFuture();
                            }
                        }
                    }
                }
            }
        }

        @Override
        public void sessionIdle(NextFilter nextFilter, IoSession session, IdleStatus status) throws Exception {
            session.getHandler().sessionIdle(session, status);
        }

        @Override
        public void exceptionCaught(NextFilter nextFilter, IoSession session, Throwable cause) throws Exception {
            AbstractIoSession s = (AbstractIoSession) session;

            try {
                s.getHandler().exceptionCaught(s, cause);
            } finally {
                if (s.getConfig().isUseReadOperation()) {
                    s.offerFailedReadFuture(cause);
                }
            }
        }

        @Override
        public void inputClosed(NextFilter nextFilter, IoSession session) throws Exception {
            session.getHandler().inputClosed(session);
        }

        @Override
        public void messageReceived(NextFilter nextFilter, IoSession session, Object message) throws Exception {
            AbstractIoSession s = (AbstractIoSession) session;

            if (!(message instanceof IoBuffer)) {
                s.increaseReadMessages(System.currentTimeMillis());
            } else if (!((IoBuffer) message).hasRemaining()) {
                s.increaseReadMessages(System.currentTimeMillis());
            }

            // Update the statistics
            if (session.getService() instanceof AbstractIoService) {
                ((AbstractIoService) session.getService()).getStatistics().updateThroughput(System.currentTimeMillis());
            }

            // Propagate the message
            try {
                session.getHandler().messageReceived(s, message);
            } finally {
                if (s.getConfig().isUseReadOperation()) {
                    s.offerReadFuture(message);
                }
            }
        }

        @Override
        public void messageSent(NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws Exception {
            ((AbstractIoSession) session).increaseWrittenMessages(writeRequest, System.currentTimeMillis());

            // Update the statistics
            if (session.getService() instanceof AbstractIoService) {
                ((AbstractIoService) session.getService()).getStatistics().updateThroughput(System.currentTimeMillis());
            }

            // Propagate the message
            session.getHandler().messageSent(session, writeRequest.getMessage());
        }

        @Override
        public void filterWrite(NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws Exception {
            nextFilter.filterWrite(session, writeRequest);
        }

        @Override
        public void filterClose(NextFilter nextFilter, IoSession session) throws Exception {
            nextFilter.filterClose(session);
        }
    }
           

在Apache  mina中過濾鍊IoFilterChain 中最後一個TailFilter 會調用IoSession相關聯的方法。是以,IoHandler和IoFilter都是在IoProcessor線程中執行的。

IoHandler放在所有IoFilter過濾鍊最後來執行的。