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Provides classes and interfaces for the MillStone inheritable event
model. The model supports inheritable events and a flexible way of
registering and unregistering event listeners. It's a fundamental building
block of the MillStone framework, and as it is included in
{@link org.millstone.base.ui.AbstractComponent}, all UI components
automatically support it.
Package Specification
The core of the MillStone event model is the inheritable event class
hierarchy, and the {@link org.millstone.base.event.EventRouter EventRouter}
which provide a simple, ubiquitous mechanism to transport events to all
interested parties.
The power of the event inheritance arises from the possibility of
receiving not only the events of the registered type, but also the
ones which are inherited from it. For example, let's assume that there
are the events GeneralEvent and SpecializedEvent
so that the latter inherits the former. Furthermore we have an object
A which registers to receive GeneralEvent type
events from the object B. A would of course
receive all GeneralEvents generated by B, but in
addition to this, A would also receive all
SpecializedEvents generated by B. However, if
B generates some other events that do not have
GeneralEvent as an ancestor, A would not receive
them unless it registers to listen for them, too.
The interface to attaching and detaching listeners to and from an object
works with methods. One specifies the event that should trigger the listener,
the trigger method that should be called when a suitable event occurs and the
object owning the method. From these a new listener is constructed and added
to the event router of the specified component.
The interface is defined in
{@link org.millstone.base.event.MethodEventSource MethodEventSource}, and a
straightforward implementation of it is defined in
{@link org.millstone.base.event.EventRouter EventRouter} which also includes
a method to actually fire the events.
All fired events are passed to all registered listeners, which are of
type {@link org.millstone.base.event.ListenerMethod ListenerMethod}. The
listener then checks if the event type matches with the specified event
type and calls the specified trigger method if it does.
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