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From Kevin.Bed...@sunlife.com
Subject RE: DAO or ... ? [Scanned for known viruses]
Date Tue, 15 Oct 2002 18:55:37 GMT




Not sure - I didn't really look at that in the design. I liked how this
approach allowed me to modify the form bean and/or the Value Object without
having to make any changes to the Action class.

I was trying to create an instructive example, not so much create the
ultimate design. We had covered DynaActionForms elsewhere and I didn't want
to do too much at once. The real goal was definition of the facade and
model components.

The biggest value is using this pattern to define a clean break between the
Action class and the Model components - i.e., the facade in front of the
web service. By doing this, you create a design where changing the back-end
system - a little or a lot - has little to no effect on the Action class.

I do like your idea of a reusable class. Expecially if I had a bunch of
forms to process.





Dan Cancro <DCancro@bridgespan.com> on 10/15/2002 02:47:59 PM

Please respond to "Struts Users Mailing List"
       <struts-user@jakarta.apache.org>

To:    "'Struts Users Mailing List'" <struts-user@jakarta.apache.org>
cc:     (bcc: Kevin Bedell/Systems/USHO/SunLife)
Subject:    RE: DAO or ... ? [Scanned for known viruses]


Would it better/worse to move the getValueObject() method out of
CustomerForm.java, so you could use DynaActionForms and not have to write
CustomerForm.java?  Maybe it could go in a reusable class that knows how to
get various ValueObjects from various DynaActionForms.

Thanks,
Dan

> -----Original Message-----
> From: Kevin.Bedell@sunlife.com [mailto:Kevin.Bedell@sunlife.com]
> Sent: Monday, October 14, 2002 11:13 AM
> To: Struts Users Mailing List
> Subject: RE: DAO or ... ? [Scanned for known viruses]
>
>
>
>
>
>
> James -
>
> I've attached a few files from my upcoming book Struts Kick Start that
> provide a basic design pattern that sounds like it may be
> similar to what
> your describing.
>
> What I do is:
>
>  - Create a Value Object that encapsulates data communicated
> with the Model
> component.
>
>  - Create a facade class that accepts and returns value
> objects through
> 'business methods'. By defining the facade to work at a
> 'business method'
> level, it helps keep any code related to a particular
> persistence layer or
> back-end system out of the Action class. This also addresses
> the issues you
> described of 'designing to test' - the clean seperation
> between the Action
> class and the Model components that the Facade provides
> simplifies testing.
>
>  - Create the form bean to provide set/get methods that also
> accept and
> return value objects - this greatly simplifies the Action class and
> isolates it from changes.
>
> The Action class (a bit simplified - I've taken out detailed
> comments and
> exception handling) goes something like:
>
>       // cast the form bean
>       CustomerForm cf = (CustomerForm) form;
>
>       // Create a facade to interface to the back-end system
>       CustomerWSFacade facade = new CustomerWSFacade();
>
>       // Extract the value object from the form bean
>       CustomerValueObject cvo = cf.getValueObject();
>
>       // Pass the value object to the facade. It returns an
> update value object
>       cvo = facade.addressChange( cvo );
>
>       // Use the returned value object to update the values
> in the form bean.
>       cf.setValueObject(cvo);
>
> These particular classes come from the chapter on providing
> integration
> with Axis for Web Services. Another chapter uses the identical set of
> classes to communicate with JBoss using a Session Bean - all I did was
> write a different facade class. The point of this was to demonstrate a
> design that made it very simple to perform maintenance or
> changes on the
> back-end or persistence layer.
>
>
>
> Regarding testing - I'd recommend you take a look at the
> StrutsTestCase
> project at sourceforge - it provides some great templates for
> both JUnit
> and Cactus tests that are designed for Struts. Makes
> JUnit/Cactus testing
> pretty straightforward. A copy of this and detailed
> directions also come
> with the book.
>
>       http://strutstestcase.sourceforge.net/
>
>
> Best of luck -
> Kevin
>
>
> Author, Struts Kick Start
>
> (See attached file: customer.zip)
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> "Couball, James" <James.Couball@cotelligent.com> on
> 10/14/2002 01:19:16 PM
>
> Please respond to "Struts Users Mailing List"
>        <struts-user@jakarta.apache.org>
>
> To:    "'Struts Users Mailing List'" <struts-user@jakarta.apache.org>
> cc:     (bcc: Kevin Bedell/Systems/USHO/SunLife)
> Subject:    RE: DAO or ... ?
>
>
> I recommend taking a look at the Session Fa├žade pattern in
> the Java Blue
> Prints.  No matter if you use EJBs or not, this pattern
> encapsulates the
> ideas that Simon was mentioning.
>
> Does anyone know the name of the more general pattern that
> doesn't involve
> Session Beans specifically?
>
> One of my general concerns is "design to test".  I like to be
> able to test
> the (business/persistence) layer that the actions will call
> independently
> of
> struts, actions, etc.  Encapsulating that layer in an API (or
> wrapping with
> a session bean) makes this possible.
>
> Sincerely,
> James.
>
> > -----Original Message-----
> > From: Andrew Hill [mailto:andrew.david.hill@gridnode.com]
> > Sent: Monday, October 14, 2002 8:16 AM
> > To: Struts Users Mailing List
> > Subject: RE: DAO or ... ?
> >
> > But you still call the API from the action right - is this
> not invoking
> > the
> > functionality that persists your data?
> >
> > Seems a bit like semantic juggling to me... (after all the
> persistance
> > layer
> > is just an abstraction API on top of writing to db/disk/punchcard
> > itself...)
> > ;-)
> >
> > I would however agree that there ought to be some sort of
> abstracting
> > layer
> > between the view and the implementation specific details of
> the p-tier...
> >
> > -----Original Message-----
> > From: Chappell, Simon P [mailto:Simon.Chappell@landsend.com]
> > Sent: Monday, October 14, 2002 23:04
> > To: Struts Users Mailing List; andrew.david.hill@gridnode.com
> > Subject: RE: DAO or ... ?
> >
> >
> > You invoke your persistence code in the same place that you
> would invoke
> > any
> > other code ... not in the Action!
> >
> > Write all your core application code (business rules, persistence,
> > communications etc) in a way that has no connection to the
> view portion
> of
> > your system and then create a API to it. This way you can
> have any client
> > you like call into your core code and your core code doesn't need to
> worry
> > about what calls it, only about acting upon requests.
> >
> > Then use the actions to call into the API and pass the API
> return values
> > to
> > the JSPs. Works great.
> >
> > /------\    /---\   /----\
> > |Client|--> |API|-->|Core|
> > |Code  |    |   |   |Code|
> > \------/    \---/   \----/
> >
> > The API is now your fire break. Nothing on the Core Code side has to
> worry
> > about displaying anything and nothing in the Client Code
> has to worry
> > about
> > calculating anything.
> >
> > Simon
> >
> > -----------------------------------------------------------------
> > Simon P. Chappell                     simon.chappell@landsend.com
> > Java Programming Specialist                      www.landsend.com
> > Lands' End, Inc.                                   (608) 935-4526
> >
> >
> > >-----Original Message-----
> > >From: Andrew Hill [mailto:andrew.david.hill@gridnode.com]
> > >Sent: Monday, October 14, 2002 9:57 AM
> > >To: Struts Users Mailing List
> > >Subject: RE: DAO or ... ?
> > >
> > >
> > >So where should one invoke the persistance layer?
> > >
> > >-----Original Message-----
> > >From: Lacerda, Wellington (AFIS)
> [mailto:Wellington.Lacerda@fao.org]
> > >Sent: Monday, October 14, 2002 22:51
> > >To: 'Struts Users Mailing List'
> > >Subject: RE: DAO or ... ?
> > >Importance: High
> > >
> > >
> > >Hi Kevin
> > >
> > >Avoid persistence in Action code as much as you can.
> > >
> > >This is the general recommendation.
> > >
> > >Wellington Silva
> > >Author of "JSP and Tag Libraries for Web Development"
> > >FAO of the UN - Consultant
> > >
> > >-----Original Message-----
> > >From: Kevin Viet [mailto:vietk@activia.net]
> > >Sent: Monday, October 14, 2002 4:45 PM
> > >To: struts-user
> > >Subject: DAO or ... ?
> > >
> > >
> > >My question is a web app design question.
> > >What pattern you guys follow when you want to save a
> domain object in
> > >the database ?:
> > >
> > >- use the DAO pattern of java blueprint  (persistence
> layer is called
> > >into classes)
> > >- call to persistence statements into action code :
> > >
> > >   // store example
> > >   try {
> > >         PeristenceLayer pl = getPerstitenceLayer();
> > >         pl.save(domainObject);
> > >   }
> > >   catch (Exception
> > >
> > >
> > >--
> > >Kevin Viet <vietk@activia.net>
> > >ActiVia Networks
> > >
> > >
> > >
> > >
> > >--
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