[Engine-devel] [engine-devel] frontend builders proposal

Wed Jan 30 09:11:41 UTC 2013

> this dialog demonstrates the greatest difference (IMHO) between server side pages to applets,
> the back and forth filling the form by retrieving all elements one by one.
> I would think of a concept similar to server side pages, i.e. retrieving all
> data, visibility and even validations (compat?), in a single request, and let the
> server have the logic.
Not sure if I have understood you correctly - do you mean moving the frontend logic (e.g. visibility of fields according to some selection) and also the frontend models
to the server? I would say it is better to have this on FE. 

However having the validations common between FE and BE would be great. We could prepare a different patch for this.

----- Original Message -----
From: "Gilad Chaplik" <gchaplik at redhat.com>
To: "Tomas Jelinek" <tjelinek at redhat.com>
Cc: engine-devel at ovirt.org, "Eli Mesika" <emesika at redhat.com>
Sent: Monday, January 28, 2013 5:08:41 PM
Subject: Re: [Engine-devel] [engine-devel] frontend builders proposal

----- Original Message -----
> From: "Eli Mesika" <emesika at redhat.com>
> To: "Tomas Jelinek" <tjelinek at redhat.com>
> Cc: engine-devel at ovirt.org
> Sent: Saturday, January 26, 2013 10:58:57 PM
> Subject: Re: [Engine-devel] [engine-devel] frontend builders proposal
> 
> 
> 
> ----- Original Message -----
> > From: "Tomas Jelinek" <tjelinek at redhat.com>
> > To: engine-devel at ovirt.org
> > Sent: Friday, January 25, 2013 11:55:43 AM
> > Subject: [Engine-devel] [engine-devel] frontend builders proposal
> > 
> > Hi All,
> > 
> > as many of you may know, the way how the frontend and backend
> > models
> > are built on frontend (uicommonweb project) is not really ideal.
> > Currently this logic is copy pasted over and over again to
> > different
> > places where it is needed with minor changes to fulfill the
> > specific
> > requirements. It is not only aesthetically problematic, but I
> > recall
> > tons of bugs caused by introducing a new field and forgetting to
> > add
> > it to every place it is used in GUI.
> > 
> > Now, as there will be big changes in the VM/Template models
> > (http://www.ovirt.org/Features/Instance_Types), so the way how the
> > VM, Template, Pool and also the newly created Instance Types models
> > are being built has to be touched anyhow, it is a great opportunity
> > to rethink the way how we do it.
> > 
> > I have created a simple infrastructure
> > (http://gerrit.ovirt.org/#/c/10874/) which could be used for it,
> > and
> > a PoC patch which uses this infrastructure
> > (http://gerrit.ovirt.org/#/c/11354/). Please note that the PoC is
> > not really impressive in means of removing duplications, I wanted
> > to
> > start with the simplest possibility.
> > 
> > The principles behind the infrastructure:
> > - have small, well named, easy to understand and reuse builders
> > - this builders can be chained together or embedded to each other
> > to
> > build the full resulting object (composite pattern)
> > - this builders can be asynchronous, and the next builder in the
> > chain has to be executed only when the current is completely done
> > 
> > The structure:
> > - the base is an interface called Builder which has a method
> > build(source, destination, rest)
> > - the builder implementing this interface
> >   + will get the source and destination objects
> >   + copies whatever he wants from source to destination
> >   + when done, executes build on the first element of the rest
> >     + this may sound awkward, but this is the way how the async
> >     calls
> >     can be "linearized" in a general way, not embedding anonymous
> >     class into anonymous
> >       class into anonymous class... as we do it today.
> >     + for synchronous builders, there is a BaseSyncBuilder which
> >     takes care of this boilerplate calling of next and exposes a
> >     simple method
> >       build(S source, D destination)
> >   + to simplify the creating and running the chain of builders,
> >   there
> >   is a BuilderExecutor class (can be created as sync or async)
> > 
> > So, a simple example - even more simple than the PoC patch :)
> > 
> > //create the first builder
> > class FirstLetterBuilder extends BaseSyncBuilder<String,
> > StringBuilder> {
> >  @Override
> >  protected void build(String source, StringBuilder destination) {
> >      // copy the first letter to the destination
> >      destination.append(source.charAt(0));
> >  }
> > }
> > 
> > //create the second builder
> > class SecondLetterBuilder extends BaseSyncBuilder<String,
> > StringBuilder> {
> >  @Override
> >  protected void build(String source, StringBuilder destination) {
> >      // copy the second letter to the destination
> >      destination.append(source.charAt(1));
> >  }
> > }
> > 
> > // usage
> > ...
> > // create the destination object
> > StringBuilder res = new StringBuilder();
> > 
> > // configure the executor with the two builders
> > BuilderExecutor<String, StringBuilder> executor = new
> > BuilderExecutor<String, StringBuilder>(
> >         new FirstLetterBuilder(),
> >         new SecondLetterBuilder()
> >         );
> > 
> > // execute the builder chain ("ab" is the source, res the
> > destination)
> > executor.build("ab", res);
> > 
> > // use the result
> > ...
> > 
> > That's it. And the nice part is, that this FirstLetterBuilder and
> > SecondLetterBuilder can be reused anywhere or combined with any
> > other builders.
> > 
> > Any comments on this will be more than welcome!
> 
> great and really simplifies work and eliminate bugs resulted from
> copy/past code
> gave +1
> Thanks
> Eli

Hi guys,

I agree that this refactoring can significantly help us reduce code complexity,
there is another issue that your suggestion doesn't address, 
but we may want take the opportunity to address it if we are already considering refactoring for this code:
this dialog demonstrates the greatest difference (IMHO) between server side pages to applets,
the back and forth filling the form by retrieving all elements one by one.
I would think of a concept similar to server side pages, i.e. retrieving all
data, visibility and even validations (compat?), in a single request, and let the
server have the logic.

Thanks, 
Gilad.

> > 
> > Thank you,
> > Tomas
> > _______________________________________________
> > Engine-devel mailing list
> > Engine-devel at ovirt.org
> > http://lists.ovirt.org/mailman/listinfo/engine-devel
> > 
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