clientcommunicatoradmin.java

java1.6众多例子参考

/*
 * @(#)ClientCommunicatorAdmin.java	1.16 05/12/29
 * 
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package com.sun.jmx.remote.internal;

import java.io.IOException;
import java.io.InterruptedIOException;

import com.sun.jmx.remote.util.ClassLogger;
import com.sun.jmx.remote.util.EnvHelp;

public abstract class ClientCommunicatorAdmin {
    public ClientCommunicatorAdmin(long period) {
	this.period = period;

	if (period > 0) {
	    checker = new Checker();

	    Thread t = new Thread(checker);
	    t.setDaemon(true);
	    t.start();
	} else
	    checker = null;
    }

    /**
     * Called by a client to inform of getting an IOException.
     */
    public void gotIOException (IOException ioe) throws IOException {
	restart(ioe);
    }

    /**
     * Called by this class to check a client connection.
     */
    protected abstract void checkConnection() throws IOException;

    /**
     * Tells a client to re-start again.
     */
    protected abstract void doStart() throws IOException;

    /**
     * Tells a client to stop because failing to call checkConnection.
     */
    protected abstract void doStop();

    /**
     * Terminates this object.
     */
    public void terminate() {
	synchronized(lock) {
	    if (state == TERMINATED) {
		return;
	    }

	    state = TERMINATED;

	    lock.notifyAll();

	    if (checker != null)
		checker.stop();
	}
    }

    private void restart(IOException ioe) throws IOException {
	// check state
	synchronized(lock) {
	    if (state == TERMINATED) {
		throw new IOException("The client has been closed.");
	    } else if (state == FAILED) { // already failed to re-start by another thread
		throw ioe;
	    } else if (state == RE_CONNECTING) {
		// restart process has been called by another thread
		// we need to wait
		while(state == RE_CONNECTING) {
		    try {
			lock.wait();
		    } catch (InterruptedException ire) {
			// be asked to give up
			InterruptedIOException iioe = new InterruptedIOException(ire.toString());
			EnvHelp.initCause(iioe, ire);

			throw iioe;
		    }
		}

		if (state == TERMINATED) {
		    throw new IOException("The client has been closed.");
		} else if (state != CONNECTED) {
		    // restarted is failed by another thread
		    throw ioe;
		}
	    } else {
		state = RE_CONNECTING;
		lock.notifyAll();
	    }
	}

	// re-starting
	try {
	    doStart();
	    synchronized(lock) {
		if (state == TERMINATED) {
		    throw new IOException("The client has been closed.");
		}

		state = CONNECTED;

		lock.notifyAll();
	    }

	    return;
	} catch (Exception e) {
	    logger.warning("restart", "Failed to restart: " + e);
	    logger.debug("restart",e);

	    synchronized(lock) {
		if (state == TERMINATED) {
		    throw new IOException("The client has been closed.");
		}

		state = FAILED;

		lock.notifyAll();
	    }

	    try {
		doStop();
	    } catch (Exception eee) {
		// OK.
		// We know there is a problem.
	    }

	    terminate();

	    throw ioe;
	}
    }

// --------------------------------------------------------------
// private varaibles
// --------------------------------------------------------------
    private class Checker implements Runnable {
	public void run() {
	    myThread = Thread.currentThread();

	    while (state != TERMINATED && !myThread.isInterrupted()) {
		try {
		    Thread.sleep(period);
		} catch (InterruptedException ire) {
		    // OK.
		    // We will check the state at the following steps
		}

		if (state == TERMINATED || myThread.isInterrupted()) {
		    break;
		}

		try {
		    checkConnection();
		} catch (Exception e) {
		    synchronized(lock) {
			if (state == TERMINATED || myThread.isInterrupted()) {
			    break;
			}
		    }

		    e = (Exception)EnvHelp.getCause(e);

		    if (e instanceof IOException && 
			!(e instanceof InterruptedIOException)) {
			try {
			    restart((IOException)e);
			} catch (Exception ee) {
			    logger.warning("Checker-run", 
					   "Failed to check connection: "+ e);
			    logger.warning("Checker-run", "stopping");
			    logger.debug("Checker-run",e);
			    
			    break;
			}
		    } else {
			logger.warning("Checker-run", 
				     "Failed to check the connection: " + e);
			logger.debug("Checker-run",e);

			// XXX stop checking?

			break;
		    }
		}
	    }

	    if (logger.traceOn()) {
		logger.trace("Checker-run", "Finished.");
	    }
	}

	private void stop() {
	    if (myThread != null && myThread != Thread.currentThread()) {
		myThread.interrupt();
	    }
	}

	private Thread myThread;
    }

// --------------------------------------------------------------
// private variables
// --------------------------------------------------------------
    private final Checker checker;
    private long period;

    // state
    private final static int CONNECTED = 0;
    private final static int RE_CONNECTING = 1;
    private final static int FAILED = 2;
    private final static int TERMINATED = 3;

    private int state = CONNECTED;

    private final int[] lock = new int[0];

    private static final ClassLogger logger = 
	new ClassLogger("javax.management.remote.misc", 
			"ClientCommunicatorAdmin");
}