[919] | 1 | /**
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| 2 | * EntitySaveManager.java
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| 3 | * Copyright (C) 2010 New Zealand Digital Library, http://expeditee.org
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| 4 | *
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| 5 | * This program is free software: you can redistribute it and/or modify
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| 6 | * it under the terms of the GNU General Public License as published by
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| 7 | * the Free Software Foundation, either version 3 of the License, or
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| 8 | * (at your option) any later version.
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| 9 | *
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| 10 | * This program is distributed in the hope that it will be useful,
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| 11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 13 | * GNU General Public License for more details.
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| 14 | *
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| 15 | * You should have received a copy of the GNU General Public License
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| 16 | * along with this program. If not, see <http://www.gnu.org/licenses/>.
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| 17 | */
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| 18 |
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[140] | 19 | package org.expeditee.taskmanagement;
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| 20 |
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| 21 | import java.util.Collection;
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| 22 | import java.util.HashSet;
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| 23 | import java.util.LinkedList;
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| 24 | import java.util.Set;
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| 25 |
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| 26 |
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| 27 | /**
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[1102] | 28 | * Manages time/resource-consuming saving procedures. For entities in an expeditee Frame that
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[140] | 29 | * requires heavy-duty saving, implement the entity as a SaveableEntity.
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| 30 | *
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| 31 | * The convention used:
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| 32 | *
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| 33 | * Register a SaveableEntity only if there is a possibility that it might need to be saved
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| 34 | * at the next save point.
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| 35 | *
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| 36 | * There are two save points:
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| 37 | * <ul>
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| 38 | * <li>Everytime the current frame is changed.
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| 39 | * <li>When the application exits.
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| 40 | * </ul>
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| 41 | *
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| 42 | * @author Brook Novak
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| 43 | */
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| 44 | public class EntitySaveManager {
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| 45 |
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| 46 | /**
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| 47 | * Singleton design pattern
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| 48 | */
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| 49 | private static EntitySaveManager _instance = new EntitySaveManager();
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| 50 | public static EntitySaveManager getInstance() {
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| 51 | return _instance;
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| 52 | }
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| 53 |
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| 54 | private Set<SaveableEntity> entitiesToSave = new HashSet<SaveableEntity>();
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| 55 | private SaveThread saveThread = null;
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| 56 | private Set<SaveStateChangedEventListener> listeners = new HashSet<SaveStateChangedEventListener>();
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| 57 |
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| 58 | /**
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| 59 | * Adds a SaveStateChangedEventListener.
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| 60 | *
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| 61 | * @see notes in removeSaveStateChangedEventListener
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| 62 | *
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| 63 | * @param listener
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| 64 | * The listener to add
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| 65 | *
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| 66 | * @throws NullPointerException
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| 67 | * If listener is null
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| 68 | */
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| 69 | public void addSaveStateChangedEventListener(SaveStateChangedEventListener listener) {
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| 70 | if (listener == null) throw new NullPointerException("listener");
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| 71 | synchronized(listeners) {
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| 72 | listeners.add(listener);
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| 73 | }
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| 74 | }
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| 75 |
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| 76 | /**
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| 77 | * Removes a SaveStateChangedEventListener.
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| 78 | *
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| 79 | * This is important if your SaveStateChangedEventListener is temporarily used -
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| 80 | * as this is a singleton and will thus keep the SaveStateChangedEventListener
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| 81 | * in memory until it is explicity removed (due to java garbage collection).
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| 82 | *
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| 83 | * @param listener
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| 84 | * The listener to add
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| 85 | *
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| 86 | * @throws NullPointerException
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| 87 | * If listener is null
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| 88 | */
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| 89 | public void removeSaveStateChangedEventListener(SaveStateChangedEventListener listener) {
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| 90 | if (listener == null) throw new NullPointerException("listener");
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| 91 | synchronized(listeners) {
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| 92 | listeners.remove(listener);
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| 93 | }
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| 94 | }
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| 95 |
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| 96 | /**
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| 97 | * Adds an entity for saving at the next save point.
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| 98 | *
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| 99 | * @param entity
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| 100 | * The entity to save
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| 101 | *
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| 102 | * @return
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| 103 | * True if added. False if already registered.
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| 104 | *
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| 105 | * @throws NullPointerException
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| 106 | * If entity is null
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| 107 | */
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| 108 | public boolean register(SaveableEntity entity) {
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| 109 | if (entity == null) throw new NullPointerException("entity");
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| 110 | return entitiesToSave.add(entity);
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| 111 | }
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| 112 |
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| 113 | /**
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| 114 | * Removes an entity from saving at the next save point.
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| 115 | * Note that if in the process of saving or is about to save, then it will not be removed.
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| 116 | * In such cases it is up to the entity to ignore the save command.
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| 117 | *
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| 118 | * @param entity
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| 119 | * The entity to cancel save
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| 120 | *
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| 121 | * @return
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| 122 | * True if added. False if already registered.
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| 123 | *
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| 124 | * @throws NullPointerException
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| 125 | * If entity is null
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| 126 | */
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| 127 | public boolean unregister(SaveableEntity entity) {
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| 128 | if (entity == null) throw new NullPointerException("entity");
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| 129 | return entitiesToSave.remove(entity);
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| 130 | }
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| 131 |
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| 132 | /**
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| 133 | * Saves all current registered entities and clears registrations.
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| 134 | *
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[1102] | 135 | * Returns immediately.
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[140] | 136 | */
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| 137 | public synchronized void saveAll() {
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| 138 | if (entitiesToSave.isEmpty()) return;
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| 139 |
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| 140 | // Get list of entities that needs sacing
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| 141 | LinkedList<SaveableEntity> toSave = new LinkedList<SaveableEntity>();
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| 142 | for (SaveableEntity entity : entitiesToSave) {
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| 143 | if (entity.doesNeedSaving()) toSave.add(entity);
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| 144 | }
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| 145 | entitiesToSave.clear();
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| 146 |
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| 147 | if (toSave.isEmpty()) return;
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| 148 |
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| 149 | // If already saving
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| 150 | if (saveThread != null && saveThread.isAlive()) {
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| 151 | // Add the extras
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| 152 | saveThread.addMoreToSave(toSave);
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| 153 |
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| 154 | // If did not finish while adding extras then return...
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| 155 | if (!saveThread.isFinished) {
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| 156 | return;
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| 157 | }
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| 158 | }
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| 159 |
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| 160 | // Start saving
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| 161 | saveThread = new SaveThread(toSave);
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| 162 | saveThread.start();
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| 163 | }
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| 164 |
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| 165 | /**
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| 166 | * If something is saving, this will block the thread until all entities that
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[1102] | 167 | * have been requested to be saved has finished their saving processes.
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[140] | 168 | *
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| 169 | * @throws InterruptedException
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| 170 | * If any thread has interrupted the current thread.
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| 171 | * Note: The interrupted status of the current thread is cleared when this exception is thrown
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| 172 | */
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| 173 | public void waitUntilAllSavingFinished() throws InterruptedException {
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| 174 | if (saveThread != null && saveThread.isAlive()) {
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| 175 | saveThread.join();
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| 176 | }
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| 177 | }
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| 178 |
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| 179 | /**
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| 180 | * Non-daemon thread for asynchronously saving heavy duty save procs.
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| 181 | *
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| 182 | * @author Brook Novak
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| 183 | */
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| 184 | private class SaveThread extends Thread {
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| 185 |
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| 186 | private LinkedList<SaveableEntity> toSave = new LinkedList<SaveableEntity>();
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| 187 | private boolean isFinished = false;
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| 188 |
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| 189 | SaveThread(Collection<SaveableEntity> toSave) {
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| 190 | super("SaveThread");
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| 191 |
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| 192 | this.toSave.addAll(toSave);
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| 193 | }
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| 194 |
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| 195 | /**
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| 196 | * Adds more entities to save.
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| 197 | *
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| 198 | * Note: due to my limited knowledge of java threading I have assumed that
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| 199 | * it is possible for the thread to end after the call without having saved
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| 200 | * the given extras. Thus check the isFinished - where if true then it indicates
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| 201 | * that the extras may not have saved.
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| 202 | *
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| 203 | * @param extra Extra entities to save.
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| 204 | */
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| 205 | public void addMoreToSave(Collection<SaveableEntity> extra) {
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| 206 | assert(extra != null);
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| 207 |
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| 208 | synchronized(toSave) {
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| 209 | for (SaveableEntity entity : extra) {
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| 210 | if (!toSave.contains(entity)) {
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| 211 | toSave.add(entity);
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| 212 | }
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| 213 | }
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| 214 | }
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| 215 | }
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| 216 |
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| 217 | @Override
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| 218 | public void run() {
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| 219 |
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| 220 | // Keep running until saved all entities.
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| 221 | while (true) {
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| 222 | SaveableEntity entity = null;
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| 223 | synchronized(toSave) {
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| 224 |
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| 225 | if (toSave.isEmpty()) {
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| 226 | isFinished = true; // safety check
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| 227 | return;
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| 228 | }
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| 229 |
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| 230 | entity = toSave.remove();
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| 231 | }
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| 232 |
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| 233 | assert(entity != null);
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| 234 |
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| 235 | if (entity.doesNeedSaving()) {
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| 236 |
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[1102] | 237 | // notify observers that save has started
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| 238 | (new SafeFireEvent(entity, true)).run();
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[140] | 239 |
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| 240 | // Complete the save
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| 241 | try {
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| 242 | entity.performSave();
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| 243 | } catch (Exception e) { // safety
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| 244 | e.printStackTrace();
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| 245 | }
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| 246 |
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| 247 | // notify observers that save has finished - on swing thread
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[1102] | 248 | (new SafeFireEvent(entity, false)).run();
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[140] | 249 | }
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| 250 | }
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| 251 | }
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| 252 |
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| 253 | /**
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[1102] | 254 | * Notifies all listeners of save start/completion event when run.
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[140] | 255 | *
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| 256 | * @author Brook Novak
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| 257 | *
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| 258 | */
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| 259 | private class SafeFireEvent implements Runnable {
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| 260 |
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| 261 | private SaveableEntity entity;
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| 262 | private boolean started;
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| 263 |
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| 264 | SafeFireEvent(SaveableEntity entity, boolean started) {
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| 265 | this.entity = entity;
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| 266 | this.started = started;
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| 267 | }
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| 268 |
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| 269 | public void run() {
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| 270 | synchronized(listeners) {
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| 271 | for (SaveStateChangedEventListener listener : listeners) {
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| 272 | if (started) listener.saveStarted(new SaveStateChangedEvent(this, entity));
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| 273 | else listener.saveCompleted(new SaveStateChangedEvent(this, entity));
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| 274 | }
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| 275 | }
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| 276 | }
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| 277 |
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| 278 | }
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| 279 |
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| 280 |
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| 281 | }
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| 282 |
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| 283 | }
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