|
Plugin Framework
The extensibility system provides a framework for both, providing extensibility hooks,
and for extending the functionality of Columba.
A plugin is a bundle of extensions. An extension provides an implementation of a
specific functionality.
The {@link IPluginManager} manages all plugins as a singleton registry. Additionally, it
is also a registry for all available extension handlers. {@link IExtensionHandler} is a
registry for extensions. It resembles an extension point or hook to extend Columba's
functionality. {@IExtension} provides the metadata, describing an extensions.
Additionally, it is responsible for instanciating an extension. Every extension must
implement the interface {@link IExtensionInterface}.
When looking at {@link IExtensionHandler}, its obvious that it simply resembles a
registry for classes. All extensions have a unique id and the classname. The
extension handler keeps a hashtable of all extensions and uses a custom classloader
to instanciate extensions.
All extension handlers use xml files which can be found in /res directory.
This is merely an easy way to specify extensions easily, without hardcoding them in
Java. A list of all extension points for the core package can be found in:
org.columba.core.plugin.pluginhandler.xml. All core extension handler
files can be found in org.columba.core.plugin.
This is an example extension handler file:
Usually, when making use of extensions in Columba, you first get an instance of the
plugin manager using PluginManager.getInstance(). Then you have to
retrieve an appropriate extension handler getHandler(id). Using this
handler, you get the extension using IExtensionHandler.getExtension(id).
Now, you instanciate the plugin using IExtension.instanciate().
|