abstractpollingconnectionlessioacceptor.java

mina是以Java实现的一个开源的网络程序框架

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 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
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 *  Unless required by applicable law or agreed to in writing,
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 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
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package org.apache.mina.core.polling;

import java.net.SocketAddress;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.Set;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.Executor;

import org.apache.mina.core.RuntimeIoException;
import org.apache.mina.core.buffer.IoBuffer;
import org.apache.mina.core.future.IoFuture;
import org.apache.mina.core.service.AbstractIoAcceptor;
import org.apache.mina.core.service.IoAcceptor;
import org.apache.mina.core.service.IoProcessor;
import org.apache.mina.core.session.AbstractIoSession;
import org.apache.mina.core.session.ExpiringSessionRecycler;
import org.apache.mina.core.session.IoSession;
import org.apache.mina.core.session.IoSessionConfig;
import org.apache.mina.core.session.IoSessionRecycler;
import org.apache.mina.core.write.WriteRequest;
import org.apache.mina.core.write.WriteRequestQueue;
import org.apache.mina.util.ExceptionMonitor;

/**
 * TODO Add documentation
 * {@link IoAcceptor} for datagram transport (UDP/IP).
 *
 * @author The Apache MINA Project ([e-mail])
 * @version $Rev: 751504 $, $Date: 2009-03-08 20:24:58 +0100 (Sun, 08 Mar 2009) $
 * @org.apache.xbean.XBean
 */
public abstract class AbstractPollingConnectionlessIoAcceptor<T extends AbstractIoSession, H>
        extends AbstractIoAcceptor {

    private static final IoSessionRecycler DEFAULT_RECYCLER = new ExpiringSessionRecycler();

    private final Object lock = new Object();
    private final IoProcessor<T> processor = new ConnectionlessAcceptorProcessor();
    private final Queue<AcceptorOperationFuture> registerQueue =
        new ConcurrentLinkedQueue<AcceptorOperationFuture>();
    private final Queue<AcceptorOperationFuture> cancelQueue =
        new ConcurrentLinkedQueue<AcceptorOperationFuture>();
    private final Queue<T> flushingSessions = new ConcurrentLinkedQueue<T>();
    private final Map<SocketAddress, H> boundHandles =
        Collections.synchronizedMap(new HashMap<SocketAddress, H>());

    private IoSessionRecycler sessionRecycler = DEFAULT_RECYCLER;

    private final ServiceOperationFuture disposalFuture =
        new ServiceOperationFuture();
    private volatile boolean selectable;
    
    /** The thread responsible of accepting incoming requests */ 
    private Acceptor acceptor;

    private long lastIdleCheckTime;

    /**
     * Creates a new instance.
     */
    protected AbstractPollingConnectionlessIoAcceptor(IoSessionConfig sessionConfig) {
        this(sessionConfig, null);
    }

    /**
     * Creates a new instance.
     */
    protected AbstractPollingConnectionlessIoAcceptor(IoSessionConfig sessionConfig, Executor executor) {
        super(sessionConfig, executor);

        try {
            init();
            selectable = true;
        } catch (RuntimeException e){
            throw e;
        } catch (Exception e) {
            throw new RuntimeIoException("Failed to initialize.", e);
        } finally {
            if (!selectable) {
                try {
                    destroy();
                } catch (Exception e) {
                    ExceptionMonitor.getInstance().exceptionCaught(e);
                }
            }
        }
    }

    protected abstract void init() throws Exception;
    protected abstract void destroy() throws Exception;
    protected abstract int select() throws Exception;
    protected abstract int select(int timeout) throws Exception;
    protected abstract void wakeup();
    protected abstract Iterator<H> selectedHandles();
    protected abstract H open(SocketAddress localAddress) throws Exception;
    protected abstract void close(H handle) throws Exception;
    protected abstract SocketAddress localAddress(H handle) throws Exception;
    protected abstract boolean isReadable(H handle);
    protected abstract boolean isWritable(H handle);
    protected abstract SocketAddress receive(H handle, IoBuffer buffer) throws Exception;
    protected abstract int send(T session, IoBuffer buffer, SocketAddress remoteAddress) throws Exception;
    protected abstract T newSession(IoProcessor<T> processor, H handle, SocketAddress remoteAddress) throws Exception;
    protected abstract void setInterestedInWrite(T session, boolean interested) throws Exception;

    /**
     * {@inheritDoc}
     */
    @Override
    protected IoFuture dispose0() throws Exception {
        unbind();
        if (!disposalFuture.isDone()) {
            startupAcceptor();
            wakeup();
        }
        return disposalFuture;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected final Set<SocketAddress> bindInternal(
            List<? extends SocketAddress> localAddresses) throws Exception {
        // Create a bind request as a Future operation. When the selector
        // have handled the registration, it will signal this future.
        AcceptorOperationFuture request = new AcceptorOperationFuture(localAddresses);

        // adds the Registration request to the queue for the Workers
        // to handle
        registerQueue.add(request);

        // creates the Acceptor instance and has the local
        // executor kick it off.
        startupAcceptor();
        
        // As we just started the acceptor, we have to unblock the select()
        // in order to process the bind request we just have added to the 
        // registerQueue.
        wakeup();

        // Now, we wait until this request is completed.
        request.awaitUninterruptibly();

        if (request.getException() != null) {
            throw request.getException();
        }

        // Update the local addresses.
        // setLocalAddresses() shouldn't be called from the worker thread
        // because of deadlock.
        Set<SocketAddress> newLocalAddresses = new HashSet<SocketAddress>();

        for (H handle:boundHandles.values()) {
            newLocalAddresses.add(localAddress(handle));
        }
        
        return newLocalAddresses;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected final void unbind0(
            List<? extends SocketAddress> localAddresses) throws Exception {
        AcceptorOperationFuture request = new AcceptorOperationFuture(localAddresses);

        cancelQueue.add(request);
        startupAcceptor();
        wakeup();

        request.awaitUninterruptibly();

        if (request.getException() != null) {
            throw request.getException();
        }
    }

    /**
     * {@inheritDoc}
     */
    public final IoSession newSession(SocketAddress remoteAddress, SocketAddress localAddress) {
        if (isDisposing()) {
            throw new IllegalStateException("Already disposed.");
        }

        if (remoteAddress == null) {
            throw new NullPointerException("remoteAddress");
        }

        synchronized (bindLock) {
            if (!isActive()) {
                throw new IllegalStateException(
                        "Can't create a session from a unbound service.");
            }

            try {
                return newSessionWithoutLock(remoteAddress, localAddress);
            } catch (RuntimeException e) {
                throw e;
            } catch (Error e) {
                throw e;
            } catch (Exception e) {
                throw new RuntimeIoException("Failed to create a session.", e);
            }
        }
    }

    private IoSession newSessionWithoutLock(
            SocketAddress remoteAddress, SocketAddress localAddress) throws Exception {
        H handle = boundHandles.get(localAddress);
        if (handle == null) {
            throw new IllegalArgumentException("Unknown local address: " + localAddress);
        }

        IoSession session;
        IoSessionRecycler sessionRecycler = getSessionRecycler();
        synchronized (sessionRecycler) {
            session = sessionRecycler.recycle(localAddress, remoteAddress);
            if (session != null) {
                return session;
            }

            // If a new session needs to be created.
            T newSession = newSession(processor, handle, remoteAddress);
            getSessionRecycler().put(newSession);
            session = newSession;
        }

        initSession(session, null, null);

        try {
            this.getFilterChainBuilder().buildFilterChain(session.getFilterChain());
            getListeners().fireSessionCreated(session);
        } catch (Throwable t) {
            ExceptionMonitor.getInstance().exceptionCaught(t);
        }

        return session;
    }

    public final IoSessionRecycler getSessionRecycler() {
        return sessionRecycler;
    }

    public final void setSessionRecycler(IoSessionRecycler sessionRecycler) {
        synchronized (bindLock) {
            if (isActive()) {
                throw new IllegalStateException(
                        "sessionRecycler can't be set while the acceptor is bound.");
            }

            if (sessionRecycler == null) {
                sessionRecycler = DEFAULT_RECYCLER;
            }
            this.sessionRecycler = sessionRecycler;
        }
    }

    private class ConnectionlessAcceptorProcessor implements IoProcessor<T> {

        public void add(T session) {
        }

        public void flush(T session) {
            if (scheduleFlush(session)) {
                wakeup();
            }
        }

        public void remove(T session) {
            getSessionRecycler().remove(session);
            getListeners().fireSessionDestroyed(session);
        }