Command
Command encapsulates a request as an object, thereby letting you parameterize
clients with different requests, queue or log requests, and support undoable
operations. Commands are an object oriented replacement for callbacks.
Examples:
Swing Action Objects.
Swing uses Command pattern to separate the GUI components from the actual code
which processes the generated events. You can configure a JButton object
with a concrete Action implementation which can then forward the request
to an object implementing the application logic.
In this example, the JButton acts as an Invoker, calling the
actionPerformed method of a concrete Action (Command) object.
The JButton instance is not aware of the object that actually handles
the command request.
The Action object then delegates the call to a Receiver
object which does not know who issued the request but knows how to process it.
The receiver object can be modified or completely changed to another object
without affecting the code in JButton. Similarly, new objects sending
the requests can be added without affecting the Receiver object.
Last Updated: $Date: 2000/07/29 18:03:07 $ by $Author: jpl $