Hookom, Jacob wrote:
You threw me for a loop with replying so late to that email--
It just comes down to giving the developer the ability to scale their own
layers with JSF like you said below. If I want ActionForms, then I will
have JSF update request/session scope beans that are only for the view. If
I want something simpler, then I can have JSF update my business beans
themselves.
JSP->View Logic/Beans->Business Logic/Beans
JSP->Business Logic/Beans
PS: Craig, did you get my email to Ed Burns and yourself about a new, faster
JSF-specific EL implementation for JSF RI?
I did indeed. I'm sure Ed will look at it next week, after Sun returns
to operation from our shutdown this week.
Best Regards,
Jacob Hookom
Craig
-----Original Message-----
From: Craig McClanahan [mailto:[EMAIL PROTECTED]
Sent: Thursday, July 08, 2004 7:35 PM
To: Struts Users Mailing List
Subject: Re: Theoretical debate
Hookom, Jacob wrote:
Look at JSF, do you have actions? No, JSF just updates your POJO beans and
calls methods on them. Why have an ActionForm or have to create all of
these Actions that are simply getter/setter adapters? Please don't be too
quick to retort to my supposed anti-struts mindset, but there are other
frameworks out there that allow direct interaction with my business objects
and don't require a heck of a lot of framework specific coding.
(Coming into this discussion late, but figured that my experience on
both the Struts and JSF side of things might provide some illuminating
food for thought :-)
It's instructive, first, to go back to the beginning of Struts
development (just over four years ago), and recall why an ActionForm
exists in the first place. The only reason we created that abstraction
was to deal with some pesky real world problems in designing webapps ...
primarily dealing with conversion (where we really punted ... see
below), validation, and little things like maintaining the state of
checkboxes. Because Struts doesn't have any "user interface component"
concept, dealing with those things had to go somewhere -- and a common
abstraction at least made it easy to understand.
Therefore, the recommended design pattern for a Struts based app becomes:
- An ActionForm per input <form>, normally with
String-based properties (so you can redisplay
invalid input the way users expect you to).
- A set of validation rules that are applied for you
on the server side, and optionally also on the
client side.
- If a validation error occurs, Struts takes care
of redisplaying the page (with error messages)
- If validation succeeds, the application Action
is responsibe for performing conversions of the
String valued things in the ActionForm to match
the underlying model data types, typically by
copying them in to DTO/VO type objects and
passing them to business logic (although, as others
have pointed out, lots of Struts developers have
skipped this extra layer).
With JSF, the component model takes care of all the responsibilities
that Struts uses an ActionForm for, so you don't need one any more.
Indeed, I anticipate people will choose one or more (they aren't
mutually exclusive) of at least three different styles for building
JSF-based webapps:
(1) You can bind individual *components* to backing bean properties,
similar to how ASP.Net "code behind files" work. This will
be most comfortable to VB developers, and is useful when
you need to programmatically modify component properties.
(2) You can bind component *values* directly to properties in your
backing bean, and then provide the business logic as action methods
in the same class. Because the components take care of conversion,
you're free to use model-oriented data types for such properties,
so you don't need to worry about explicit conversion any more.
This style will appear to Struts developers like a combination of an
Action and an ActionForm in the same class, and will also appeal to
the crowd that likes O-O encapsulation :-).
(3) You can bind component *values* directly to properties on a VO/DTO
object, and bind action events to methods on a separate bean that will
either perform the logic directly or delegate to a business logic
class.
This style will feel more like traditional Struts separated
ActionForm and
Action classes, but the Action won't have as much to do. It's also
a great
way to build a webapp on top of existing application infrastructure
that
provides resuabe VO/DTO and business logic classes already.
I believe that all three approaches are valid -- which one you take for
a particular application function depends on your use case for that
function. You don't have to be exclusive, either. Combine them where
it makes sense.
Craig McClanahan
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