Hi,
I have a design doubt... I must validate data coming from a form. This
consist typically of:
  - 'format' validations (i.e. a field is not empty or it is numeric)
that I do in the validate method of the ActionForm
  - 'business' validations that usually require a DB access

I actually do 2 steps (actions) per operation. One of them prepare the
data and the second one does the operation itself. And here comes my
first question: ��is there any other better aproach?? Maybe something
similar to a Tiles Controller to prepare the data...

  class PreOperationAction extends Action {
    public ... execute ( ... ) {
      // Create JavaBeans to populate html selects and several
inputs (requires DB access) and include them in the request
      // Forward to error/success jsp
    }
  }

  class PostOperationAction extends Action {
    public ... execute ( ... ) {
      // Get data from ActionForm
      // Business validations (the selected values and inputs are
valid from the business point of view)
      // Execute business logic (encapsulated in external business
logic classes)
      // Forward to error/success jsp
    }
  }

At this point I don't know what is better (from a MVC perspective).
  1. Do it as actually, that is, doing business validation before
business logic. This way I think I can't expose the business logic as an
API or as a web service.
  2. Include all the validations (business and format) into the
business logic classes. This way I must duplicate format validations
  3. Doing a OperationValidations class (? only a vague idea)
  4. Is there any pattern or any best practice related? Does
Validator Plugin allow complex business validations?

Finally, I need your opinion about handling validation errors:
  1. Throwing an Exception from the business logic classes and catch
it in the Action (or declare the exception in struts-config.xml)
  2. Returning null (or -1, or a no-sense value) from the business
logic classes
  3. Any other way...

Thank you very much,
Guido Garc�a Bernardo.

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