This is exactly where I wanted the conversation to go!
So Peter - if you did have a flex app, and you wanted to save a user what
would you do? At minimum you would have to pass in a struct of user values
to some webservice - but then what? Would you validate in that method? Or
would you have your flex controller first call a validate() webservice
method, then depending on the results the save() webservice method?
Brian I see you handle the inherent problem by having a custom RESULT
structure that you return - I understand why you do this - cuz I do it too -
but doesn't it kinda suck? When do you stop using it? At one point I was
thinking that I should use it as a return for any service function. The
object would have properties like: Status, MessageCode, Payload. This would
let me handle almost any cases and keep a standard interface to interact
with.
Baz
On Jan 15, 2008 11:15 AM, Peter Bell <[EMAIL PROTECTED]> wrote:
> Hi Brian,
>
> I'll disagree with you here. The calling code has to know three things:
>
> - How to pass information to the service in the format it wants
> - How to tell whether the save succeeded
> - How to pass any error messages in a way the display will want to
> see them (actually, it'll probably just be a conduit for the information,
> so
> it is more likely the view will have to know this).
>
>
> It needs to know how to pass well formed data to the service otherwise the
> save won't work. It needs to tell whether the save succeeded as otherwise it
> won't be able to make the controller decision to say whether to cflocation
> to another screen or to redisplay the form (or whatever approach you're
> using), and it needs to pass the errors along in a way the view can
> understand as otherwise the view won't be able to display the correct error
> messages.
>
> So, whether you make it:
> If UserService.isValid()
> UserService.save();
> location("UserList");
> Else
> Display Form
>
> OR
>
> Success = UserService.Save()
> If Success
> location("UserList")
> Else
> DisplayForm
>
> (o rmore likely, a variant where "Success" is really ErrorCollection and
> you test whether ErrorCollection has any members, or is ErrorBean and test
> whether ErrorBean.hasErrors())
>
> In any of these cases you are performing both a command and a query. The
> command is to save the data and the query is whether it was saved
> successfully. Nothing wrong with turning that into a single mixed method
> call (some purists might say you should keep commands and queries separated,
> but I'm not that picky), but it isn't reducing the amount of information
> required or the knowledge of the API. You're just doing the command and the
> query in a single line so it isn't making the controller any dumber – just
> more concise.
>
> Best Wishes,
> Peter
>
>
>
> On 1/15/08 12:56 PM, "Brian Kotek" <[EMAIL PROTECTED]> wrote:
>
>
>
> On Jan 15, 2008 11:57 AM, Adam Haskell <[EMAIL PROTECTED]> wrote:
>
> I'm much more comfortable with doing 2 calls in my service, model.validate();
> model.save(), instead of Model.save() and have the save do the validation.
> Doing model.save makes my service not much more a facade which isn't what
> I want. Additionally in our environment we have multiple validaters, some of
> which should not, in my opinion, be part of the domain's concern. An example
> of this would be Enterprise vs domain specific validation. Something like
> name is 35 characters and does not have cross sit scripting is Enterprise
> concerns and part of the validation across all applications irregardless of
> domain. Where as address must be in the US is domain specific to Contest
> entries. The converse is true too though if you put too much in the service
> layer your domain model becomes anemic.
>
>
> See, I disagree here. I don't think it should be the job of the calling
> code to know that this is a two step process. I would call
> myService.save(someData)
> and the validation would happen inside the model. If you have some
> higher-level validation that would take place outside of the actual business
> object, I would still do that in the service; that is its job. I would do
> that validation inside the service, or more probably I would build it into
> the Validators, which means the Validator might internally be leveraging
> several specific Validators to do it's job. So I might do
>
> myService.save(userData);
>
> and inside the service I might do:
>
> user = createUser(userData);
> result = createResult();
> if (user.isValid()) {
> result.setSuccess(true);
> }
> else {
> result.addErrorMessages (user.getErrorMessages());
> result.setOriginalData(userData);
> }
> return result;
>
>
>
>
>
> Adam Haskell
>
>
>
> On Jan 15, 2008 8:31 AM, Alan Livie < [EMAIL PROTECTED]> wrote:
>
>
> Good anecdote but I am confused!
>
> You said 'in this case the
> Service should be earning it's keep and making sure the documents are
> valid
> and ready for it's client, the model. '
>
> Are you sure about this? Shouldn't the model be responsible for making
> sure things are valid - ie look after itself.
>
> I see the service more as a smart api that delegates to the model for
> all the business logic and also can provide 'application-specific'
> functionality like logging, email notifications etc
>
> But maybe I'm misunderstanding it or taking the anecdote too
> seriously! It's more accurate than the MVC song at least :-)
>
> Alan
>
> On Jan 15, 12:47 pm, "Adam Haskell" <[EMAIL PROTECTED]> wrote:
> > I've used this anecdote before, and I think it is amusing so I'll use it
>
> > again. The way I think about it is The model and View are going through
> a
> > divorce and the controller and service are the lawyers. Now thinking
> about
> > it in these terms, would it make sense for the Controller (the View's
> > lawyer) to be taking care of the Model's Affairs, in this case
> validating
> > documents for the model? That doesn't make much sense, in this case the
> > Service should be earning it's keep and making sure the documents are
> valid
> > and ready for it's client, the model. Sure the Controller might throw in
>
> > some JS for the View to do some preliminary checking so the always
> bitchy,
> > soon-to-be ex, spouse won't complain but it really is the spouses
> lawyer's
> > duty to inform the spouse that the documents are valid, or return the
> > documents to some one telling them to try again, no deal. That being
> said
> > Brian's earlier statement about calling something from Flex really has
> > helped me clear up what should go where. Anecdotes provide a means to
> > getting over the hump but once you are over the hump real life
> programming
> > drives the point home and Brian's example/thought process is spot on.
> >
> > Adam Haskell
> >
> > On Jan 14, 2008 11:53 PM, Brian Kotek <[EMAIL PROTECTED]> wrote:
> >
> > > It depends on what you mean by "appropriate methods", but if you're
> > > talking about something similar to what Peter used an an example:
> >
> > > If (Order.isValid())
> > > {
> > > Order.save();
> > > }
> > > Else
> > > {
> > > Screen = OrderForm;
> > > Data = Order;
> > > };
> >
> > > No, I wouldn't be doing that in the Controller (and I think we might
> be
> > > getting some miscommunication here because I'm pretty sure Peter and
> Sean
> > > wouldn't either). My Controllers are very dumb. The only thing they do
> is
> > > ask the Model to perform some business logic (via the service layer),
> and
> > > then invoke the appropriate views or execute a redirect. That covers
> 99% of
> > > what my Controllers do.
> >
> > > The problem with doing something like the above in the Controller
> means
> > > that the model is no longer neutral and self-contained. I can't call
> the
> > > service layer from Flex now, because the logic that checks validity
> and does
> > > saving is executed by the Controller, not the Model. I would have a
> method
> > > in my service named something like " orderService.saveOrder
> (orderData)",
> > > and internally that service layer method might create an Order,
> validate it,
> > > save it, and return a success or failure result that the Controller
> can then
> > > use to determine how to proceed (cflocation or redisplay form with
> errors,
> > > for example). I'm pretty sure that this is what Sean and Peter are
> also
> > > talking about.
> >
> > > On Jan 14, 2008 9:11 PM, Baz <[EMAIL PROTECTED]> wrote:
> >
> > > > Sean, Brian, it seems you are both on board with getting a
> newUserBean()
> > > > from the service in the controller then calling the appropriate
> methods on
> > > > that UserBean later on in the controller. Do you also handle queries
> or
> > > > multiple objects in the same way that Peter does? That is, do you
> code
> > > > gateway-type methods into your service that interact with a
> DAO/Gateway to
> > > > return multiple instances of your object?
> >
> > > > Baz
> >
> > > > On Jan 14, 2008 4:40 PM, Brian Kotek < [EMAIL PROTECTED]
> <mailto:[EMAIL PROTECTED]> <[EMAIL PROTECTED]> > wrote:
> >
> > > > > Absolutely, I didn't mean to imply that the service actually does
> > > > > everything itself.
> >
> > > > > On Jan 14, 2008 7:35 PM, Sean Corfield < [EMAIL PROTECTED] >
> > > > > wrote:
> >
> > > > > > On Jan 14, 2008 1:19 PM, Brian Kotek < [EMAIL PROTECTED]>
> wrote:
> > > > > > > I think he is saying that his controllers only interact with
> > > > > > services. The
> > > > > > > easy rule of thumb for me is: if this was called by Flex
> instead
> > > > > > of my HTML
> > > > > > > controller, would it still work? The answer should be "yes".
> Which
> > > > > > means all
> > > > > > > logic of any consequence (beyond doing something like a
> > > > > > cflocation, which is
> > > > > > > specific to the HTML view anyway) should be handled in the
> model.
> >
> > > > > > Right, but that can still be in the domain object rather than
> the
> > > > > > service. You just need to expose the API via the service for
> remote
> > > > > > interaction. It doesn't mean all the business logic is in the
> > > > > > *service* which is at the heart of Baz's question, I believe.
> > > > > > --
> > > > > > Sean A Corfield -- (904) 302-SEAN
> > > > > > An Architect's View --http://corfield.org/
> >
> > > > > > "If you're not annoying somebody, you're not really alive."
> > > > > > -- Margaret Atwood
>
>
>
>
>
>
>
>
>
>
> >
>
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