Mercurial > hg > blitz_condensed
diff src/com/go/trove/net/InetAddressResolver.java @ 0:3dc0c5604566
Initial checkin of blitz 2.0 fcs - no installer yet.
author | Dan Creswell <dan.creswell@gmail.com> |
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date | Sat, 21 Mar 2009 11:00:06 +0000 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/com/go/trove/net/InetAddressResolver.java Sat Mar 21 11:00:06 2009 +0000 @@ -0,0 +1,211 @@ +/* ==================================================================== + * Trove - Copyright (c) 1997-2000 Walt Disney Internet Group + * ==================================================================== + * The Tea Software License, Version 1.1 + * + * Copyright (c) 2000 Walt Disney Internet Group. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * + * 3. The end-user documentation included with the redistribution, + * if any, must include the following acknowledgment: + * "This product includes software developed by the + * Walt Disney Internet Group (http://opensource.go.com/)." + * Alternately, this acknowledgment may appear in the software itself, + * if and wherever such third-party acknowledgments normally appear. + * + * 4. The names "Tea", "TeaServlet", "Kettle", "Trove" and "BeanDoc" must + * not be used to endorse or promote products derived from this + * software without prior written permission. For written + * permission, please contact opensource@dig.com. + * + * 5. Products derived from this software may not be called "Tea", + * "TeaServlet", "Kettle" or "Trove", nor may "Tea", "TeaServlet", + * "Kettle", "Trove" or "BeanDoc" appear in their name, without prior + * written permission of the Walt Disney Internet Group. + * + * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED + * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE + * DISCLAIMED. IN NO EVENT SHALL THE WALT DISNEY INTERNET GROUP OR ITS + * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, + * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, + * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR + * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY + * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + * ==================================================================== + * + * For more information about Tea, please see http://opensource.go.com/. + */ + +package com.go.trove.net; + +import java.net.*; +import java.util.*; +import java.lang.ref.*; +import com.go.trove.util.SoftHashMap; + +/****************************************************************************** + * Allows network host names to resolve to inet addresses via event + * notification. + * <p> + * Note: This class makes use of the java.util.Timer class, available only in + * Java 2, version 1.3. + * + * @author Brian S O'Neill + * @version + * <!--$$Revision: 1.1 $-->, <!--$$JustDate:--> 01/01/23 <!-- $--> + */ +public class InetAddressResolver { + // Wait for 10 minutes before trying to resolve again. + private static final long RESOLVE_PERIOD = 10 * 60 * 1000; + private static Timer cResolveTimer; + + private static Map cResolvers = new SoftHashMap(); + + private static Timer getResolveTimer() { + Timer timer = cResolveTimer; + if (timer == null) { + timer = new Timer(true); + timer.schedule(new TimerTask() { + public void run() { + Thread.currentThread().setName("InetAddressResolver"); + } + }, 0); + cResolveTimer = timer; + } + return timer; + } + + /** + * Resolve the host name into InetAddresses and listen for changes. + * The caller must save a reference to the resolver to prevent it from + * being reclaimed by the garbage collector. + * + * @param host host to resolve into InetAddresses + * @param listener listens for InetAddresses + */ + public static InetAddressResolver listenFor(String host, + InetAddressListener listener) { + synchronized (cResolvers) { + InetAddressResolver resolver = + (InetAddressResolver)cResolvers.get(host); + if (resolver == null) { + resolver = new InetAddressResolver(host); + cResolvers.put(host, resolver); + } + resolver.addListener(listener); + return resolver; + } + } + + private final String mHost; + + private List mListeners = new ArrayList(); + + // Is either an instance of UnknownHostException or InetAddress[]. + private Object mResolutionResults; + + private InetAddressResolver(String host) { + mHost = host; + + // Initial delay is random so that requests against other hosts are + // staggered. + long delay = (long)(Math.random() * RESOLVE_PERIOD); + getResolveTimer().schedule(new Resolver(this), delay, RESOLVE_PERIOD); + } + + private synchronized void addListener(InetAddressListener listener) { + mListeners.add(listener); + if (!resolveAddresses()) { + // Ensure that new listener is called the first time. + notifyListener(listener); + } + } + + private synchronized void notifyListener(InetAddressListener listener) { + if (mResolutionResults instanceof UnknownHostException) { + listener.unknown((UnknownHostException)mResolutionResults); + } + else { + InetAddress[] addresses = (InetAddress[])mResolutionResults; + addresses = (InetAddress[])addresses.clone(); + listener.resolved(addresses); + } + } + + // Returns true if anything changed from the last time this was invoked. + private synchronized boolean resolveAddresses() { + boolean changed; + try { + InetAddress[] addresses = InetAddress.getAllByName(mHost); + if (mResolutionResults instanceof UnknownHostException) { + changed = true; + } + else { + // Results may be ordered differently, so keep them sorted. + Arrays.sort(addresses, new Comparator() { + public int compare(Object a, Object b) { + return ((InetAddress)a).getHostAddress() + .compareTo(((InetAddress)b).getHostAddress()); + } + }); + + changed = !Arrays.equals + (addresses, (InetAddress[])mResolutionResults); + } + mResolutionResults = addresses; + } + catch (UnknownHostException e) { + changed = !(mResolutionResults instanceof UnknownHostException); + mResolutionResults = e; + } + + if (changed) { + int size = mListeners.size(); + for (int i=0; i<size; i++) { + notifyListener((InetAddressListener)mListeners.get(i)); + } + } + + return changed; + } + + private class Resolver extends TimerTask { + // Weakly references owner so that the timer won't prevent it from + // being garbage collected. + private final Reference mOwner; + + public Resolver(InetAddressResolver owner) { + mOwner = new WeakReference(owner); + } + + public void run() { + InetAddressResolver owner = (InetAddressResolver)mOwner.get(); + if (owner == null) { + cancel(); + } + Thread t = Thread.currentThread(); + String originalName = t.getName(); + t.setName("InetAddressResolver:" + owner.mHost); + try { + owner.resolveAddresses(); + } + finally { + t.setName(originalName); + } + } + } +}