I want to know if there exist a form generator that is capable of generating forms, mark validator(s) for element and whole form (or some like that) and been able to generate a json object and be filled with a json object.
If possible without any external large dependencies (like crafted by hand).
For clarification: the form should be made in client side javascript from an json object if possible.
If you're okay with using PHP, then I would highly recommend php-form-builder-class. I'm not exactly sure what you mean by "external dependencies", but pfbc is pretty lightweight.