Source for gnu.java.util.prefs.MemoryBasedPreferences

   1: /* MemoryBasedPreferences - A Preference node which holds all entries in memory
   2:    Copyright (C) 2001, 2006 Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: package gnu.java.util.prefs;
  39: 
  40: import java.util.HashMap;
  41: 
  42: import java.util.prefs.*;
  43: 
  44: /**
  45:  * A Preference node which holds all entries in memory
  46:  *
  47:  * @author Mark Wielaard (mark@klomp.org)
  48:  */
  49: public class MemoryBasedPreferences extends AbstractPreferences {
  50: 
  51:     /** True if this is a preference node in the user tree, false otherwise. */
  52:     private final boolean isUser;
  53: 
  54:     /** Contains all the preference entries of this node. */
  55:     private HashMap<String, String> entries = new HashMap<String, String>();
  56: 
  57:     /**
  58:      * Creates a new preferences node with the given name and parent.
  59:      * When isUser is true it will be user node otherwise it will be a system
  60:      * node. It will always set the <code>newNode</code> field to true
  61:      * since there is no real backing store, so all nodes are new.
  62:      */
  63:     public MemoryBasedPreferences(MemoryBasedPreferences parent,
  64:                                   String name,
  65:                                   boolean isUser) {
  66:         super(parent, name);
  67:         this.isUser = isUser;
  68: 
  69:         // Since we do not have a real backing store all nodes are new
  70:         newNode = true;
  71:     }
  72: 
  73:     /**
  74:      * Returns true if this node was created as a user node.
  75:      */
  76:     public boolean isUserNode() {
  77:         return isUser;
  78:     }
  79: 
  80:     /**
  81:      * Returns an empty array since all children names are always already
  82:      * cached.
  83:      */
  84:     protected String[] childrenNamesSpi() throws BackingStoreException {
  85:         return new String[0];
  86:     }
  87: 
  88:     /**
  89:      * Returns a new node with the given name with as parent this node and
  90:      * with the <code>isUser</code> flag set to the same value as this node.
  91:      */
  92:     protected AbstractPreferences childSpi(String childName) {
  93:        return new MemoryBasedPreferences(this, childName, isUser);
  94:     }
  95: 
  96:     /**
  97:      * Returns a (possibly empty) array of keys of the preferences entries of
  98:      * this node.
  99:      */
 100:     protected String[] keysSpi() throws BackingStoreException {
 101:         return entries.keySet().toArray(new String[entries.size()]);
 102:     }
 103: 
 104:     /**
 105:      * Returns the associated value from this nodes preferences entries or
 106:      * null when the key has not been set.
 107:      */
 108:     protected String getSpi(String key) {
 109:         return entries.get(key);
 110:     }
 111: 
 112:     /**
 113:      * Sets the value for the given key.
 114:      */
 115:     protected void putSpi(String key, String value) {
 116:         entries.put(key, value);
 117:     }
 118: 
 119:     /**
 120:      * Removes the entry with the given key.
 121:      */
 122:     protected void removeSpi(String key) {
 123:         entries.remove(key);
 124:     }
 125: 
 126:     /**
 127:      * Does nothing since we do not have any backing store.
 128:      */
 129:     protected void flushSpi() {
 130:     }
 131: 
 132:     /**
 133:      * Does nothing since we do not have any backing store.
 134:      */
 135:     protected void syncSpi() {
 136:     }
 137: 
 138:     /**
 139:      * Just removes the entries map of this node.
 140:      */
 141:     protected void removeNodeSpi() {
 142:         entries = null;
 143:     }
 144: }