Eclipse 3.1 Plug-in Migration FAQ

  1. IPreferenceStore has more explicit API
  2. IWorkbenchWindow#getShell() has more explicit API

IPreferenceStore has more explicit API

Although the behavior of the IPreferenceStore provided by AbstractUIPlugin#getPreferenceStore() hasn't changed we have updated the specification of IPreferenceStore to explicitly define the behavior that we have provided.

Typing of PropertyChangeEvents

Any property change event from an IPreferenceStore must have an old and new value of the same type that is consistent with the setValue call that generated it.

For instance if you call IPreferenceStore#setValue(String name, long value) the values in the PropertyChangeEvent generated from this method will both be of type java.lang.Long.

putValue

Calls to #putValue will not generate a PropertyChangedEvent. Calls to the various #setValue methods will.

Relationship between the OSGI Preference and an IPreferenceStore

The IPreferenceStore provided by AbstractUIPlugin#getPreferenceStore()is an instance of ScopedPreferenceStore which uses org.osgi.service.prefs.Preferences as a back end. org.osgi.service.prefs.Preferences propagates change events as Strings only.

The ScopedPreferenceStore wrappers those OSGI events generated by IPreferenceStore#setValue(String name, String value) and one of it's own PropertyChangeEvents and forwards that event to it's listeners. For the other implementations of IPreferenceStore#setValue the ScopedPreferenceStore will create it's own events of the correct type and not propagate the events from the OSGI preferences.

Listeners to a ScopedPreferenceStore should be prepared for both typed and String values in thier change events as it is still possible to get an event via the OSGI preferences (during a preference import for instance). OSGI events are always of type java.lang.String.

IWorkbenchWindow#getShell() has more explict API

It has always been possible to get a null org.eclipse.swt.widgets.Shell from the existing IWorkbenchWindows in the Eclipse SDK. We now explictly define the conditions where this occurs, namely when the shell has not been created or when the IWorkbenchWindow has been closed.