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Difference between revisions of "FAQ How do I load and save plug-in preferences?"

(Current Practice)
m (Current Practice: Replaced deprecated constructor call to InstanceScope)
Line 33: Line 33:
   Preferences prefs =
   Preferences prefs =
     new InstanceScope().getNode(MY_PLUGIN_ID); // does all the above behind the scenes
     InstanceScope.INSTANCE.getNode(MY_PLUGIN_ID); // does all the above behind the scenes
   prefs.put(KEY1, this.someStr);
   prefs.put(KEY1, this.someStr);

Revision as of 10:06, 4 October 2011

The Deprecated Way

Each plug-in has a local workspace preference store for saving arbitrary primitive data types and strings. Preferences displayed in the Workbench Preferences dialog are typically stored in these local plug-in preference stores. The Import and Export buttons in the Workbench Preferences page also operate on these plug-in preference stores.

Retrieving values from plug-in preferences is fairly straightforward:

   Plugin plugin = ExamplesPlugin.getDefault();
   Preferences prefs = plugin.getPluginPreferences();
   int value = prefs.getInt("some.key");

When preferences are changed, the preference store must be explicitly saved to disk:

   prefs.setValue("some.key", 5);

The plug-in preference store can also store default values for any preference in that plug-in. If a value has not been explicitly set for a given key, the default value is returned. If the key has no default value set, a default default value is used: zero for numeric preferences, false for Boolean preferences, and the empty string for string preferences. If the default default is not appropriate for your preference keys, you should establish a default value for each key by overriding the initializeDefaultPluginPreferences method in your Plugin subclass:

   protected void initializeDefaultPluginPreferences() {
      prefs = plugin.<strike>getPluginPreferences</strike>();
      prefs.setDefault("some,key", 1);

Although you can change default values at any time, it is generally advised to keep them consistent so that users know what to expect when they revert preferences to their default values. Programmatically reverting a preference to its default value is accomplished with the setToDefault method.

Current Practice

The above technique has been deprecated since 3.1.

The current technique goes something like this:

private void savePluginSettings() {
  // saves plugin preferences at the workspace level
  Preferences prefs =
    InstanceScope.INSTANCE.getNode(MY_PLUGIN_ID); // does all the above behind the scenes

  prefs.put(KEY1, this.someStr);
  prefs.put(KEY2, this.someBool);

  try {
    // prefs are automatically flushed during a plugin's "super.stop()".
  } catch(BackingStoreException e) {
    //TODO write a real exception handler.

private void loadPluginSettings() {
  Preferences prefs = new InstanceScope().getNode(MY_PLUGIN_ID);
  // you might want to call prefs.sync() if you're worried about others changing your settings
  this.someStr = prefs.get(KEY1);
  this.someBool= prefs.getBoolean(KEY2);

See Also:

This FAQ was originally published in Official Eclipse 3.0 FAQs. Copyright 2004, Pearson Education, Inc. All rights reserved. This text is made available here under the terms of the Eclipse Public License v1.0.