Why use the command pattern in GWT (or any web app)?

According to this video here [@ 7:50] Google is recommending the use of the Command pattern on top of its request handling API. There is also a helpful looking project gwt-dispatch that implements that pattern.

According to gwt-dispatch documentation I need to create four classes for each command:

• an action (e.g. command)
• a result (e.g. response)
• an action handler
• a module

Assume my service API has 100 methods across 8 BSOs, can somebody explain to me why I want to create nearly 400 new classes? What awesomeness does this p开发者_如何学Pythonattern buy?

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• One good reason to use the command pattern is, when you want to pass the command object to further delegates - so instead of copying all the arguments, it's easier to just pass the command object around. It's also useful for gwt-dispatch's rollback functionality (or the undo/redo functionality e.g. in Eclipse's UndoableOperations).

• It helps to provide several variations of commands by using different constructors, and subclasses of commands.

• I would not suggest to always use the pattern, but you don't save as much as you think, when you don't use it: You will often need result objects anyway - and it's possible to reuse the same return objects. In other cases, you can use the same object for the command and for the result.

• The module can be used for multiple commands.