Mercurial > hg > blitz_condensed
view 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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/* ==================================================================== * 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); } } } }