[Engine-devel] Introducing generics to UiCommon

[Tomas Jelinek]

Hey all,

some time ago I have created a patch which introduces generics to UiCommon [1] and one which uses it 
in DataCenterModel [2]. Today I have changed a bit the generic version of the EntityModelTextBox to
be truly generic (since it can edit also e.g. integers) and than a simple subclass StringEntityModelTextBox
which provides the String renderer/parser to simplify the usage. All the other details are available in the previous
mail.

What do you think about it?

Tomas

[1]: http://gerrit.ovirt.org/#/c/17604/
[2]: http://gerrit.ovirt.org/#/c/17605/

----- Original Message -----
> From: "Tomas Jelinek" <tjelinek at redhat.com>
> To: "engine-devel" <engine-devel at ovirt.org>
> Sent: Monday, August 5, 2013 9:41:29 AM
> Subject: [Engine-devel]  Introducing generics to UiCommon
> 
> Hey all,
> 
> as we have passed the oVirt feature freeze I would like to celebrate it with
> a little bit of cleanup :)
> 
> A good candidate for this is to introduce generics into uicommonweb project.
> The fact that it is not generic
> brings quite some hidden expectations into our code, makes it unreadable and
> error prone.
> 
> Also, the gwt-common and both webadmin and userportal are mostly prepared to
> be generic but because the uicommonweb is not, we have code like:
> 
> new ListModelListBoxEditor<Object>(new NullSafeRenderer<Object>() {
>             @Override
>             public String renderNullSafe(Object object)
>                 return ((Version) object).getValue();
>             }
>         });
> 
> which is quite ugly and error prone.
> 
> So I have prepared two patches, one [1] which introduces the generic
> infrastructure (and prepares one widget for it, more about this below) and
> one [2] which uses it and refactors the DataCenterModel
> to use it (I have chosen this model because it is big enough to show how to
> do it and what the benefits are but small enough to be quickly review-able).
> 
> The infrastructure change:
> - changes the ListModel and EntityModel to be genreic
> - adjusts the UiCommonEditorDriverGenerator to work with generics (e.g. to
> make it aware that ListModel<String> is indeed a ListModel, same for
> EntityModel)
> - created a String version of EntityModelTextBox
> 
> The reason why the String EntityModelTextBox had to be created is that the
> EntityModelTextBox is an EditorWidget<Object, ...> so it can work only with
> EntityModel<Object>. I saw 2 ways how to make this work with
> EntityModel<String>:
> 1: Create a String version of this editor inside the .generic sub-package,
> incrementally replace the usage of the non-generic EntityModelTextBox and
> when the non-generic will be completely replaced, delete it and move the
> generic one
>    out from the generic sub-package
> 
> 2: Change the EditorWidget<Object, ...> to EditorWidget<T, ...> and replace
> each usage of the "EntityModelTextBox someWidget" by
> "EntityModelTextBox<Object> someWidget" and than incrementally replace the
> <Object> to <String> as the
>    underlying models will be refactored. After the last one will be
>    refactored, change the EditorWidget<T, ...> to EditorWidget<String, ...>
>    and replace all "EntityModelTextBox<Object> someWidget" by
>    "EntityModelTextBox someWidget"
> 
> I have chosen the first option because:
> - much less classes touched at once (e.g. much more safe)
> - the EntityModelTextBox<T> invites to use something like
> EntityModelTextBox<VM> which is not correct and fails on class cast
> exceptions
> 
> But at the same time I see the disadvantages of this approach (mostly that we
> have two versions of the same class). Please note that far not all the
> widgets will need two versions, only the ones editing only Strings which
> are declared as EditorWidget<Object> which are:
> - EntityModelLabel
> - EntityModelTextAreaLabel (used only in couple of places - can be refactored
> together without the need to have two versions)
> - EntityModelTextBox (already in the [1])
> - EntityModelPasswordBox
> - EntityModelTextArea
> - ListModelSuggestBox (used only in couple of places - can be refactored
> together without the need to have two versions)
> 
> The rest of the widgets should be already prepared to be used in generic
> environment.
> 
> Please let me know what do you think about it,
> 
> have a nice day,
> Tomas
> 
> [1]: http://gerrit.ovirt.org/#/c/17604/
> [2]: http://gerrit.ovirt.org/#/c/17605/
> 
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