| 1 | /******************************************************************************* |
| 2 | * Copyright (c) 2000, 2007 IBM Corporation and others. |
| 3 | * All rights reserved. This program and the accompanying materials |
| 4 | * are made available under the terms of the Eclipse Public License v1.0 |
| 5 | * which accompanies this distribution, and is available at |
| 6 | * http://www.eclipse.org/legal/epl-v10.html |
| 7 | * |
| 8 | * Contributors: |
| 9 | * IBM Corporation - initial API and implementation |
| 10 | *******************************************************************************/ |
| 11 | |
| 12 | package org.eclipse.ui.internal.commands; |
| 13 | |
| 14 | import org.eclipse.core.commands.IStateListener; |
| 15 | import org.eclipse.core.commands.State; |
| 16 | import org.eclipse.core.runtime.CoreException; |
| 17 | import org.eclipse.core.runtime.IConfigurationElement; |
| 18 | import org.eclipse.core.runtime.IStatus; |
| 19 | import org.eclipse.core.runtime.Status; |
| 20 | import org.eclipse.jface.commands.PersistentState; |
| 21 | import org.eclipse.jface.preference.IPreferenceStore; |
| 22 | import org.eclipse.ui.internal.WorkbenchPlugin; |
| 23 | |
| 24 | /** |
| 25 | * <p> |
| 26 | * A proxy for handler state that has been defined in XML. This delays the class |
| 27 | * loading until the state is really asked for information. Asking a proxy for |
| 28 | * anything (except disposing, and adding and removing listeners) will cause the |
| 29 | * proxy to instantiate the proxied handler. |
| 30 | * </p> |
| 31 | * <p> |
| 32 | * Loading the proxied state will automatically cause it to load its value from |
| 33 | * the preference store. Disposing of the state will cause it to persist its |
| 34 | * value. |
| 35 | * </p> |
| 36 | * <p> |
| 37 | * This class is not intended for use outside of the |
| 38 | * <code>org.eclipse.ui.workbench</code> plug-in. |
| 39 | * </p> |
| 40 | * |
| 41 | * @since 3.2 |
| 42 | */ |
| 43 | public final class CommandStateProxy extends PersistentState { |
| 44 | |
| 45 | /** |
| 46 | * The configuration element from which the state can be created. This value |
| 47 | * will exist until the element is converted into a real class -- at which |
| 48 | * point this value will be set to <code>null</code>. |
| 49 | */ |
| 50 | private IConfigurationElement configurationElement; |
| 51 | |
| 52 | /** |
| 53 | * The key in the preference store to locate the persisted state. |
| 54 | */ |
| 55 | private String preferenceKey; |
| 56 | |
| 57 | /** |
| 58 | * The preference store containing the persisted state, if any. |
| 59 | */ |
| 60 | private IPreferenceStore preferenceStore; |
| 61 | |
| 62 | /** |
| 63 | * The real state. This value is <code>null</code> until the proxy is |
| 64 | * forced to load the real state. At this point, the configuration element |
| 65 | * is converted, nulled out, and this state gains a reference. |
| 66 | */ |
| 67 | private State state = null; |
| 68 | |
| 69 | /** |
| 70 | * The name of the configuration element attribute which contains the |
| 71 | * information necessary to instantiate the real state. |
| 72 | */ |
| 73 | private final String stateAttributeName; |
| 74 | |
| 75 | /** |
| 76 | * Constructs a new instance of <code>HandlerState</code> with all the |
| 77 | * information it needs to create the real state later. |
| 78 | * |
| 79 | * @param configurationElement |
| 80 | * The configuration element from which the real class can be |
| 81 | * loaded at run-time; must not be <code>null</code>. |
| 82 | * @param stateAttributeName |
| 83 | * The name of the attribute or element containing the state |
| 84 | * executable extension; must not be <code>null</code>. |
| 85 | * @param preferenceStore |
| 86 | * The preference store to which any persistent data should be |
| 87 | * written, and from which it should be loaded; may be |
| 88 | * <code>null</code>. |
| 89 | * @param preferenceKey |
| 90 | * The key at which the persistent data is located within the |
| 91 | * preference store. |
| 92 | */ |
| 93 | public CommandStateProxy(final IConfigurationElement configurationElement, |
| 94 | final String stateAttributeName, |
| 95 | final IPreferenceStore preferenceStore, final String preferenceKey) { |
| 96 | |
| 97 | if (configurationElement == null) { |
| 98 | throw new NullPointerException( |
| 99 | "The configuration element backing a state proxy cannot be null"); //$NON-NLS-1$ |
| 100 | } |
| 101 | |
| 102 | if (stateAttributeName == null) { |
| 103 | throw new NullPointerException( |
| 104 | "The attribute containing the state class must be known"); //$NON-NLS-1$ |
| 105 | } |
| 106 | |
| 107 | this.configurationElement = configurationElement; |
| 108 | this.stateAttributeName = stateAttributeName; |
| 109 | this.preferenceKey = preferenceKey; |
| 110 | this.preferenceStore = preferenceStore; |
| 111 | } |
| 112 | |
| 113 | public final void addListener(final IStateListener listener) { |
| 114 | if (state == null) { |
| 115 | addListenerObject(listener); |
| 116 | } else { |
| 117 | state.addListener(listener); |
| 118 | } |
| 119 | } |
| 120 | |
| 121 | public final void dispose() { |
| 122 | if (state != null) { |
| 123 | state.dispose(); |
| 124 | if (state instanceof PersistentState) { |
| 125 | final PersistentState persistableState = (PersistentState) state; |
| 126 | if (persistableState.shouldPersist() && preferenceStore != null |
| 127 | && preferenceKey != null) { |
| 128 | persistableState.save(preferenceStore, preferenceKey); |
| 129 | } |
| 130 | } |
| 131 | } |
| 132 | } |
| 133 | |
| 134 | public final Object getValue() { |
| 135 | if (loadState()) { |
| 136 | return state.getValue(); |
| 137 | } |
| 138 | |
| 139 | return null; |
| 140 | } |
| 141 | |
| 142 | public final void load(final IPreferenceStore store, |
| 143 | final String preferenceKey) { |
| 144 | if (loadState() && state instanceof PersistentState) { |
| 145 | final PersistentState persistableState = (PersistentState) state; |
| 146 | if (persistableState.shouldPersist() && preferenceStore != null |
| 147 | && preferenceKey != null) { |
| 148 | persistableState.load(preferenceStore, preferenceKey); |
| 149 | } |
| 150 | } |
| 151 | } |
| 152 | |
| 153 | /** |
| 154 | * Loads the state, if possible. If the state is loaded, then the member |
| 155 | * variables are updated accordingly and the state is told to load its value |
| 156 | * from the preference store. |
| 157 | * |
| 158 | * @return <code>true</code> if the state is now non-null; |
| 159 | * <code>false</code> otherwise. |
| 160 | */ |
| 161 | private final boolean loadState() { |
| 162 | return loadState(false); |
| 163 | } |
| 164 | |
| 165 | /** |
| 166 | * Loads the state, if possible. If the state is loaded, then the member |
| 167 | * variables are updated accordingly and the state is told to load its value |
| 168 | * from the preference store. |
| 169 | * |
| 170 | * @param readPersistence |
| 171 | * Whether the persistent state for this object should be read. |
| 172 | * @return <code>true</code> if the state is now non-null; |
| 173 | * <code>false</code> otherwise. |
| 174 | */ |
| 175 | private final boolean loadState(final boolean readPersistence) { |
| 176 | if (state == null) { |
| 177 | try { |
| 178 | state = (State) configurationElement |
| 179 | .createExecutableExtension(stateAttributeName); |
| 180 | state.setId(getId()); |
| 181 | configurationElement = null; |
| 182 | |
| 183 | // Try to load the persistent state, if possible. |
| 184 | if (readPersistence && state instanceof PersistentState) { |
| 185 | final PersistentState persistentState = (PersistentState) state; |
| 186 | persistentState.setShouldPersist(true); |
| 187 | } |
| 188 | load(preferenceStore, preferenceKey); |
| 189 | |
| 190 | // Transfer the local listeners to the real state. |
| 191 | final Object[] listenerArray = getListeners(); |
| 192 | for (int i = 0; i < listenerArray.length; i++) { |
| 193 | state.addListener((IStateListener) listenerArray[i]); |
| 194 | } |
| 195 | clearListeners(); |
| 196 | |
| 197 | return true; |
| 198 | |
| 199 | } catch (final ClassCastException e) { |
| 200 | final String message = "The proxied state was the wrong class"; //$NON-NLS-1$ |
| 201 | final IStatus status = new Status(IStatus.ERROR, |
| 202 | WorkbenchPlugin.PI_WORKBENCH, 0, message, e); |
| 203 | WorkbenchPlugin.log(message, status); |
| 204 | return false; |
| 205 | |
| 206 | } catch (final CoreException e) { |
| 207 | final String message = "The proxied state for '" + configurationElement.getAttribute(stateAttributeName) //$NON-NLS-1$ |
| 208 | + "' could not be loaded"; //$NON-NLS-1$ |
| 209 | IStatus status = new Status(IStatus.ERROR, |
| 210 | WorkbenchPlugin.PI_WORKBENCH, 0, message, e); |
| 211 | WorkbenchPlugin.log(message, status); |
| 212 | return false; |
| 213 | } |
| 214 | } |
| 215 | |
| 216 | return true; |
| 217 | } |
| 218 | |
| 219 | public final void removeListener(final IStateListener listener) { |
| 220 | if (state == null) { |
| 221 | removeListenerObject(listener); |
| 222 | } else { |
| 223 | state.removeListener(listener); |
| 224 | } |
| 225 | } |
| 226 | |
| 227 | public final void save(final IPreferenceStore store, |
| 228 | final String preferenceKey) { |
| 229 | if (loadState() && state instanceof PersistentState) { |
| 230 | ((PersistentState) state).save(store, preferenceKey); |
| 231 | } |
| 232 | } |
| 233 | |
| 234 | public final void setId(final String id) { |
| 235 | super.setId(id); |
| 236 | if (state != null) { |
| 237 | state.setId(id); |
| 238 | } |
| 239 | } |
| 240 | |
| 241 | public final void setShouldPersist(final boolean persisted) { |
| 242 | if (loadState(persisted) && state instanceof PersistentState) { |
| 243 | ((PersistentState) state).setShouldPersist(persisted); |
| 244 | } |
| 245 | } |
| 246 | |
| 247 | public final void setValue(final Object value) { |
| 248 | if (loadState()) { |
| 249 | state.setValue(value); |
| 250 | } |
| 251 | } |
| 252 | |
| 253 | public final boolean shouldPersist() { |
| 254 | if (loadState() && state instanceof PersistentState) { |
| 255 | return ((PersistentState) state).shouldPersist(); |
| 256 | } |
| 257 | |
| 258 | return false; |
| 259 | } |
| 260 | |
| 261 | public final String toString() { |
| 262 | if (state == null) { |
| 263 | return configurationElement.getAttribute(stateAttributeName); |
| 264 | } |
| 265 | |
| 266 | return state.toString(); |
| 267 | } |
| 268 | } |