# Preferences

###### Identifier:

org.eclipse.equinox.preferences.preferences

###### Since:

3.0

###### Description:

The preferences extension point allows bundles to add new preference scopes to the Eclipse preference mechanism as well as specify the class to run to initialize default preference values at runtime.

###### Configuration Markup:

<!ELEMENT extension (scope* , initializer* , modifier*)>

<!ATTLIST extension

point CDATA #REQUIRED

id CDATA #IMPLIED

name CDATA #IMPLIED>

<!ELEMENT scope EMPTY>

<!ATTLIST scope

name CDATA #REQUIRED

class CDATA #IMPLIED

storage CDATA #IMPLIED>

Element describing a client's definiton of a new preference scope.

- name - The name of the scope.
- class - The name of the class.
- storage - The class which implements the preference storage.

<!ELEMENT initializer EMPTY>

<!ATTLIST initializer

class CDATA #REQUIRED>

Element which defines the class to use for runtime preference initialization.

- class - The name of the class.

<!ELEMENT modifier EMPTY>

<!ATTLIST modifier

class CDATA #REQUIRED>

Element which defines the class to use for preference modification listening.

- class - The name of the class.

###### Examples:

Following is an example of a preference scope declaration. This example declares that this plug-in will provide a preference implementation for the scope "foo". It also declares that when the default values are loaded for this plug-in, the class "MyPreferenceInitializer" contains code to be run to initialize preference default values at runtime.

          <extension point="org.eclipse.equinox.preferences.preferences">
             <scope name="foo" class="com.example.FooPrefs"/>
             <initializer class="com.example.MyPreferenceInitializer"/>
             <modifier class="com.example.MyModifyListener"/>
          </extension>

If the client chooses let the Eclipse Platform handle the preference nodes but wishes to define a custom location/mechanism for persisting the data, then they are able to set the "storage" attribute on the "scope" element. Note that only one of the "class" and "storage" attributes can be defined at the same time. The class referenced in the "storage" attribute must extend the AbstractPreferenceStorage class. In the following example the "FooStorage" class handles the loading/saving for the "foo" preferences.

          <extension point="org.eclipse.equinox.preferences.preferences">
             <scope name="foo" storage="com.example.FooStorage"/>
             <initializer class="com.example.MyPreferenceInitializer"/>
             <modifier class="com.example.MyModifyListener"/>
          </extension>

###### API Information:

The preference service (the OSGi service `org.eclipse.core.runtime.preferences.IPreferencesService`) is the hook into the Eclipse preference mechanism.

###### Supplied Implementation:

The org.eclipse.equinox.preferences bundle provides preference implementations for the "configuration", "instance", and "default" scopes. The org.eclipse.core.resources bundle provides an implementation for "project" preferences.

Copyright (c) 2004, 2014 IBM Corporation and others.
This program and the accompanying materials are made available under the terms of the Eclipse Public License 2.0 which accompanies this distribution, and is available at https://www.eclipse.org/legal/epl-v20.html/ SPDX-License-Identifier: EPL-2.0