As you may have seen, Emmanuel started a survey on how people would like to use type-level constraints in Bean Validation: http://beanvalidation.org/news/2016/11/23/survey-constraints-and-parameterized-type/

While we are waiting for some more replies to that one, I started with a PoC implementation of the value extractor idea in the reference implementation in order to get a better feeling for it, it's limitations, open questions etc.: https://github.com/hibernate/hibernate-validator/pull/592

One thing we started to wonder is whether it should be allowed to put type-level constraints to a field *and* the corresponding property getter at the same time:

    private List<@NotBlank String> strings;

    public List<@Pattern(regexp="...") String> getStrings() { return strings; }

My first inclination was to say that it should be supported (as you can put regular constraints to a field and its getter). A challenge is how to obtain the values for constraint validation. In the spirit of BV 1 we'd have to iterate the values directly from the field for evaluating the @NotBlank constraint and a second time through the getter for @Pattern validation. That's a potential performance issue of course.

What do others think?