| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information 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 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.wicket.util.watch; |
| |
| import java.util.Set; |
| import java.util.concurrent.ConcurrentHashMap; |
| |
| import org.apache.wicket.util.lang.Generics; |
| import org.apache.wicket.util.listener.ChangeListenerSet; |
| import org.apache.wicket.util.listener.IChangeListener; |
| import org.apache.wicket.util.thread.ICode; |
| import org.apache.wicket.util.thread.Task; |
| import org.apache.wicket.util.time.Duration; |
| import org.apache.wicket.util.time.Time; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| |
| /** |
| * Monitors one or more <code>IModifiable</code> objects, calling a {@link IChangeListener |
| * IChangeListener} when a given object's modification time changes. |
| * |
| * @author Jonathan Locke |
| * @since 1.2.6 |
| */ |
| public class ModificationWatcher implements IModificationWatcher |
| { |
| /** logger */ |
| private static final Logger log = LoggerFactory.getLogger(ModificationWatcher.class); |
| |
| /** maps <code>IModifiable</code> objects to <code>Entry</code> objects */ |
| private final ConcurrentHashMap<IModifiable, Entry> modifiableToEntry = Generics.newConcurrentHashMap(); |
| |
| /** the <code>Task</code> to run */ |
| private Task task; |
| |
| /** |
| * Container class for holding modifiable entries to watch. |
| */ |
| protected static final class Entry |
| { |
| // The most recent lastModificationTime polled on the object |
| public Time lastModifiedTime; |
| |
| // The set of listeners to call when the modifiable changes |
| public final ChangeListenerSet listeners = new ChangeListenerSet(); |
| |
| // The modifiable thing |
| public IModifiable modifiable; |
| } |
| |
| /** |
| * Default constructor for two-phase construction. |
| */ |
| public ModificationWatcher() |
| { |
| } |
| |
| /** |
| * Constructor that accepts a <code>Duration</code> argument representing the poll frequency. |
| * |
| * @param pollFrequency |
| * how often to check on <code>IModifiable</code>s |
| */ |
| public ModificationWatcher(final Duration pollFrequency) |
| { |
| start(pollFrequency); |
| } |
| |
| @Override |
| public final boolean add(final IModifiable modifiable, final IChangeListener listener) |
| { |
| // Look up entry for modifiable |
| final Entry entry = modifiableToEntry.get(modifiable); |
| |
| // Found it? |
| if (entry == null) |
| { |
| Time lastModifiedTime = modifiable.lastModifiedTime(); |
| if (lastModifiedTime != null) |
| { |
| // Construct new entry |
| final Entry newEntry = new Entry(); |
| |
| newEntry.modifiable = modifiable; |
| newEntry.lastModifiedTime = lastModifiedTime; |
| newEntry.listeners.add(listener); |
| |
| // Put in map |
| modifiableToEntry.putIfAbsent(modifiable, newEntry); |
| } |
| else |
| { |
| // The IModifiable is not returning a valid lastModifiedTime |
| log.info("Cannot track modifications to resource '{}'", modifiable); |
| } |
| |
| return true; |
| } |
| else |
| { |
| // Add listener to existing entry |
| return !entry.listeners.add(listener); |
| } |
| } |
| |
| @Override |
| public IModifiable remove(final IModifiable modifiable) |
| { |
| final Entry entry = modifiableToEntry.remove(modifiable); |
| if (entry != null) |
| { |
| return entry.modifiable; |
| } |
| return null; |
| } |
| |
| @Override |
| public void start(final Duration pollFrequency) |
| { |
| // Construct task with the given polling frequency |
| task = new Task("ModificationWatcher"); |
| |
| task.run(pollFrequency, new ICode() |
| { |
| @Override |
| public void run(final Logger log) |
| { |
| checkModified(); |
| } |
| }); |
| } |
| |
| /** |
| * Checks which IModifiables were modified and notifies their listeners |
| */ |
| protected void checkModified() |
| { |
| for (Entry entry : modifiableToEntry.values()) |
| { |
| // If the modifiable has been modified after the last known |
| // modification time |
| final Time modifiableLastModified = entry.modifiable.lastModifiedTime(); |
| if ((modifiableLastModified != null) && |
| modifiableLastModified.after(entry.lastModifiedTime)) |
| { |
| // Notify all listeners that the modifiable was modified |
| entry.listeners.notifyListeners(entry.modifiable); |
| |
| // Update timestamp |
| entry.lastModifiedTime = modifiableLastModified; |
| } |
| } |
| } |
| |
| @Override |
| public void destroy() |
| { |
| if (task != null) |
| { |
| // task.stop(); |
| task.interrupt(); |
| } |
| } |
| |
| @Override |
| public final Set<IModifiable> getEntries() |
| { |
| return modifiableToEntry.keySet(); |
| } |
| } |