I think the API is missing a basic class for data binding, a PropertyConverter. Basically the same as PropertyFormatter, but not converting between String and Object but between Object and Object.

One of the use cases is a slider that is bound to an integer property of a bean. This is currently not possible since the slider has a value type of Double. With a PropertyConverter class, one could easily translate between Integer and Double and set it as the property data source of the slider.

Of course it was fairly easy to create the PropertyConverter on my own, but I think it should be there by default.

The forms and property conversions have been redesigned for Vaadin 7. See
Improved Data Binding for Enterprise Applications
. The dev team is currently working on those features, so you could try them when the Vaadin 7 Alpha 2 comes out, possibly in couple of weeks.

Excellent, this is going to be a great improvement!

…and there is an add-on for it if you are living your life today: