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Scheduler/Dispatcher for a multi-threaded application.
Columba uses the CommandReference pattern. Where {@link Command} instances are decoupled
from their References ({@link DefaultCommandReference}).
Actions ({@link FrameAction}) start Commands and pass the appropriate Reference to them.
This is Preclaiming Scheduler implementation. Meaning tasks get queued until
all resources they need are free at once. Which is no problem, because for
example a "copy message from folder a to folder b" operation needs only two
resources: folder a and folder b.
The org.columba.core.command.Command class has two methods. Execute() is for
time consuming background tasks, updateGUI() is called after the execute-method
is finished (the thread is finished). The nice thing about updateGUI() is that is called
in the awt-event dispatcher thread. It is therefore thread-safe, and can be used to
update the gui.
Note, that execute() has {@link Worker} in its signature, which has a couple of methods
to display a text in the {@link Statusbar}, or updating the progressbar.
Worker registers at the {@link Taskmanager}, which is basically the model for
{@link Statusbar}.
We use an easy listener pattern to register all the workers.
This makes it easy for commands to send status updates.
Then we have actions in org.columba.core.action. These provide the glue between
the gui-elements and the commands. An action initializes a command and passes it
along to the Processor (task scheduler {@link DefaultProcessor}) to execute.
You can find many examples in the packages ending with "action" and "command".
Adapting, this schema should be pretty easy for developers.
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