comparison java/src/uk/ac/qmul/eecs/ccmi/utils/PreferencesService.java @ 0:9418ab7b7f3f

Initial import

+/*  
+ CCmI Editor - A Collaborative Cross-Modal Diagram Editing Tool
+	  
+ Copyright (C) 2002 Cay S. Horstmann (http://horstmann.com)
+ Copyright (C) 2011  Queen Mary University of London (http://ccmi.eecs.qmul.ac.uk/)
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package uk.ac.qmul.eecs.ccmi.utils;
+
+import java.util.prefs.Preferences;
+
+/**
+ * A service for storing and loading user preferences.
+ */
+public abstract class PreferencesService
+{
+   /**
+    * Gets an instance of the service, suitable for the package of the given class.
+    * @return an instance of the service
+    */
+   public static PreferencesService getInstance(){
+      if (service != null) return service;
+      try{
+         service = new DefaultPreferencesService();
+         return service;
+      }
+      catch (SecurityException exception){
+         // that happens when we run under Web Start         
+      }
+      
+      return new NullPreferencesService();
+   }
+   
+   /**
+    * Gets a previously stored string from the service.
+    * @param key the key of the string
+    * @param defval the value to return if no matching value was found
+    * @return the value stored with the given key, or defval if none was found 
+    */
+   public abstract String get(String key, String defval);
+   /**
+    * Saves a key/value pair for later retrieval.
+    * @param key the key of the string to be stored
+    * @param value the value to to be stored
+    */
+   public abstract void put(String key, String value);
+   
+   private static PreferencesService service;
+}
+
+/**
+ * The default preferences service that uses the java.util.prefs API. 
+ */
+class DefaultPreferencesService extends PreferencesService{   
+   /**
+    * Gets an instance of the service, suitable for the package of the given class.
+    * @param appClass the main application class (only the package name is used as the path to  
+    * app-specific preferences storage)
+    * @return an instance of the service
+    */
+   public DefaultPreferencesService()
+   {
+      prefs = Preferences.userNodeForPackage(this.getClass());   
+   }
+   
+   public String get(String key, String defval) { return prefs.get(key, defval); }
+   public void put(String key, String defval) { prefs.put(key, defval); }
+
+   private Preferences prefs;
+}
+
+/**
+ * The null preferences service that is returned when we are an applet. 
+ */
+class NullPreferencesService extends PreferencesService {   
+   public String get(String key, String defval) { return defval; }
+   public void put(String key, String defval) { }
+}