/*
* Copyright (c) 2008, Harald Kuhr
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * 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.
* * Neither the name "TwelveMonkeys" nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS 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 COPYRIGHT OWNER OR
* 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.
*/
package com.twelvemonkeys.util;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.net.URL;
import java.util.Timer;
import java.util.TimerTask;
import java.util.Map;
import java.util.HashMap;
// TODO: Could this be used for change-aware classloader? Woo..
/**
* Monitors changes is files and system resources.
*
* Based on example code and ideas from
* <A href="http://www.javaworld.com/javaworld/javatips/jw-javatip125.html">Java
* Tip 125: Set your timer for dynamic properties</A>.
*
* @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
* @author last modified by $Author: haku $
* @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/util/ResourceMonitor.java#1 $
*/
public abstract class ResourceMonitor {
private static final ResourceMonitor INSTANCE = new ResourceMonitor() {};
private Timer timer;
private final Map<Object, ResourceMonitorTask> timerEntries;
public static ResourceMonitor getInstance() {
return INSTANCE;
}
/**
* Creates a {@code ResourceMonitor}.
*/
protected ResourceMonitor() {
// Create timer, run timer thread as daemon...
timer = new Timer(true);
timerEntries = new HashMap<Object, ResourceMonitorTask>();
}
/**
* Add a monitored {@code Resource} with a {@code ResourceChangeListener}.
*
* The {@code reourceId} might be a {@code File} a {@code URL} or a
* {@code String} containing a file path, or a path to a resource in the
* class path. Note that class path resources are resolved using the
* given {@code ResourceChangeListener}'s {@code ClassLoader}, then
* the current {@code Thread}'s context class loader, if not found.
*
* @param pListener pListener to notify when the file changed.
* @param pResourceId id of the resource to monitor (a {@code File}
* a {@code URL} or a {@code String} containing a file path).
* @param pPeriod polling pPeriod in milliseconds.
*
* @see ClassLoader#getResource(String)
*/
public void addResourceChangeListener(ResourceChangeListener pListener,
Object pResourceId, long pPeriod) throws IOException {
// Create the task
ResourceMonitorTask task = new ResourceMonitorTask(pListener, pResourceId);
// Get unique Id
Object resourceId = getResourceId(pResourceId, pListener);
// Remove the old task for this Id, if any, and register the new one
synchronized (timerEntries) {
removeListenerInternal(resourceId);
timerEntries.put(resourceId, task);
}
timer.schedule(task, pPeriod, pPeriod);
}
/**
* Remove the {@code ResourceChangeListener} from the notification list.
*
* @param pListener the pListener to be removed.
* @param pResourceId name of the resource to monitor.
*/
public void removeResourceChangeListener(ResourceChangeListener pListener, Object pResourceId) {
synchronized (timerEntries) {
removeListenerInternal(getResourceId(pResourceId, pListener));
}
}
private void removeListenerInternal(Object pResourceId) {
ResourceMonitorTask task = timerEntries.remove(pResourceId);
if (task != null) {
task.cancel();
}
}
private Object getResourceId(Object pResourceName, ResourceChangeListener pListener) {
return pResourceName.toString() + System.identityHashCode(pListener);
}
private void fireResourceChangeEvent(ResourceChangeListener pListener, Resource pResource) {
pListener.resourceChanged(pResource);
}
/**
*
*/
private class ResourceMonitorTask extends TimerTask {
ResourceChangeListener listener;
Resource monitoredResource;
long lastModified;
public ResourceMonitorTask(ResourceChangeListener pListener, Object pResourceId) throws IOException {
listener = pListener;
lastModified = 0;
String resourceId = null;
File file = null;
URL url = null;
if (pResourceId instanceof File) {
file = (File) pResourceId;
resourceId = file.getAbsolutePath(); // For use by exception only
}
else if (pResourceId instanceof URL) {
url = (URL) pResourceId;
if ("file".equals(url.getProtocol())) {
file = new File(url.getFile());
}
resourceId = url.toExternalForm(); // For use by exception only
}
else if (pResourceId instanceof String) {
resourceId = (String) pResourceId; // This one might be looked up
file = new File(resourceId);
}
if (file != null && file.exists()) {
// Easy, this is a file
monitoredResource = new FileResource(pResourceId, file);
//System.out.println("File: " + monitoredResource);
}
else {
// No file there, but is it on CLASSPATH?
if (url == null) {
url = pListener.getClass().getClassLoader().getResource(resourceId);
}
if (url == null) {
url = Thread.currentThread().getContextClassLoader().getResource(resourceId);
}
if (url != null && "file".equals(url.getProtocol())
&& (file = new File(url.getFile())).exists()) {
// It's a file in classpath, so try this as an optimization
monitoredResource = new FileResource(pResourceId, file);
//System.out.println("File: " + monitoredResource);
}
else if (url != null) {
// No, not a file, might even be an external resource
monitoredResource = new URLResource(pResourceId, url);
//System.out.println("URL: " + monitoredResource);
}
else {
throw new FileNotFoundException(resourceId);
}
}
lastModified = monitoredResource.lastModified();
}
public void run() {
long lastModified = monitoredResource.lastModified();
if (lastModified != this.lastModified) {
this.lastModified = lastModified;
fireResourceChangeEvent(listener, monitoredResource);
}
}
}
}