Forms support

[davidsowerby]

Vaadin 8 made some improvements to Form support, primarily with the Binder class, but there is opportunity to extend that further.

Substantial changes would be needed, however. First thoughts on design ...

The binder and related actors should:

1. scan an entity for all the annotations above to produce a property descriptor
2. optionally cache the descriptor 1. it may be used many times
3. bind the Field to the entity property as Binder does now
4. set Field locale to CurrentLocale
5. set Field size, where appropriate, according to property type and validation (for example maxLength on String or max on Integer affect required field length
6. automatically select the appropriate Vaadin Field for the property data type, with an option to override the default selection with a Presentation annotation
7. ensure all presentation elements are updated in response to a Locale change
8. fully integrate Validation, I18N and presentation elements
9. enable the addition of new Validators as required
10. maybe use external standard data converters instead of Vaadin specific (perhaps Apache Commons Convert)
11. enable the addition of custom data converters as required, preferably though Guice

An entity should:

• carry annotations for JSR 380 validation, property and class level as required
• carry annotations for Krail I18N for caption and description
• carry a Presentation annotation to specify where the presentation element (Vaadin Field) is not the default

Major changes:

• Apache BVal does not seem to have a JSR 380 implementation - worth checking again, but if not, integration with Hibernate Validator will be needed. (possible example)

• Binder does some of this, but some of it is hard to integrate with. A replacement may be necessary.

[davidsowerby]

Build this on top of easyBinder

[mcollovati]

Apache BVal team seems to be working on implementing Java Bean Validation 2.0 http://bval.apache.org/board-reports/2018-03.html#activity

There is also a dedicate branch on github repository https://github.com/apache/bval/tree/bv2