Re: Design issue in swing application

Lew <>
Wed, 17 Feb 2010 13:13:32 -0500
markspace wrote:

Normally, the Controller has references to the View and the Model, not
the other way around.

public class Controller {

  View view;
  Model model;

More commonly the controller could have a collection of model classes or
instances and map of {model instance, outcome} -> {view instance} entries.

There would also be a map of {view result} -> {model instance} entries.

A framework like Struts or JSF can build the maps at deployment time.

(Note this controller now likely needs to be
synchronized and created on the EDT.)

The controller should definitely not run on the EDT. It or (preferably) the
view components it invokes should use 'invokeAndWait()'.

I agree with the bulk of your comments, however.

You may need lots of
controllers to implement a single window if that window has lots of
buttons or controls.

There are various MVC paradigms. The simple "Model 2" version (for example,
Struts) has a single front controller. More fractal versions such as JSF do
what you suggest, having multiple controllers.

Views should be "dumb" and just fire events. Don't keep any state in a
view, other than the state it already has (like the text string in a

The view may also handle surface edits and other view logic to ensure that
data that reach the controller(s) from the view are consistent.

In classic MVC, the model updates the view via a call back, and the view
has a reference to the model. However, Java uses a "split model" design

I consider "classic" the MVC paradigm that is, as you say, procedural and the
controller loop looks something like:

  public void control()
   for ( View view = initialView(); view != BYEBYE;)
     Request request = view.getRequest();
     Model model = chooseModel( request );
     Result result = model.process( request );
     view = nextView( model, result );

where 'chooseModel()' and 'nextView()' are methods in the controller and
'View' and 'Model' are interfaces with a 'getRequest()' and 'process()'
method, respectively.

When I've written Model 2 code by hand, the controller is only a couple of
hundred lines long, and most of that comprises the setup code for the maps.

where views (JComponents) have their own model. So I think it's kind of
a toss up how your model updates the view when needed. I'd be inclined
to have it go through the Controller too, meaning no direct linkage.

Exactly so.


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