Extension instantiation
To create extensions instances, PF4J uses an ExtensionFactory.
By default, PF4J uses DefaultExtensionFactory as implementation of ExtensionFactory.
You can change the default implementation with:
new DefaultPluginManager() {
@Override
protected ExtensionFactory createExtensionFactory() {
return MyExtensionFactory();
}
};
DefaultExtensionFactory uses Class#newInstance() method to create the extension instance.
An extension instance is created on demand, when plugin.getExtensions(MyExtensionPoint.class) is called.
By default, if you call plugin.getExtensions(MyExtensionPoint.class) twice:
plugin.getExtensions(MyExtensionPoint.class);
plugin.getExtensions(MyExtensionPoint.class);
then for each call, a new extension instance is created.
If you want to return the same extension instance (singleton), you need to use SingletonExtensionFactory:
new DefaultPluginManager() {
@Override
protected ExtensionFactory createExtensionFactory() {
return SingletonExtensionFactory();
}
};