Hello every,
Just a little backgrounder for this RR. For some time now, a coworker
and I have been working on and off on a library/framework to simplify
creation of GWT applications, specifically those that cover most of
our use cases. For the most part, the applications we build involve
filling out rather large forms, retrieving data, generating reports,
etc. Building these large forms by hand is very tedious, so we created
an open source project called Mount Sinai Hospital Application Builder
(mshab) which you can find here: http://code.google.com/p/mshab/.
I started to overhaul the project to make it easier to use and easier
to extend. As I started the overhaul, I noticed that the incubator
started to get populated with a lot of similar widgets and libraries
that I was redeveloping. I contacted Emily Crutcher about the
Validation aspect and we ended up talking a bit about the incubator. I
decided that it'll be best to try to commit back to the incubator so
we could avoid having to throw away our code after the incubator
implemented the same ideas. I'll start making RRs about the various
parts that we were working on to get feedback and hopefully
incorporate it into the incubator.
Now, to the meat of the post. Right now, extracting data from widgets
is very different depending on the widget. From a TextBox, you call
textBox.getText(). For a ListBox you call
listBox.getValue(listBox.getSelectedItem()). Setting the data is
different too, and sometimes pretty "complex" (ListBox involves a
loop, etc). Therefore, I'm proposing a common interface that wraps
around core GWT widgets and provides one way to extract and set data
to widgets. There are a number of use cases where this can be applied.
Some good examples are validation and simple data binding.
The interface is a straight forward generic interface that works with
a generic widget and a generic data type (comments removed):
public interface DataManager<T, S> {
public S getData(T widget);
public void setData(T widget, S data);
}
Here's an example of how it would be used to manage TextBoxBase
widgets.
public class TextBoxBaseDataManager implements
DataManager<TextBoxBase, String> {
public String getData(TextBoxBase widget) {
return widget.getText();
}
public void setData(TextBoxBase widget, String data) {
widget.setText(data);
}
}
To help developers easily get the appropriate DataManager for a
specific widget, I created a DataManagerCollection interface where you
can get the specific DataManager for a given widget and then start
working with it. The developer can either use existing
DataManagerCollection implementations or wire their own.
public interface DataManagerCollection {
public boolean hasDataManager(Widget widget);
public DataManager<?, ?> getDataManager(Widget widget);
public void setDataManager(Widget widget, DataManager<?, ?>
dataManager);
}
We're currently working on creating wrappers for all the core GWT
widgets and the incubator ones. Feedback would be much appreciated.
Thank you for your time.
Best regards,
Arthur Kalmenson
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http://groups.google.com/group/Google-Web-Toolkit-Contributors
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