[bv-dev] @Valid and group translation

[Gunnar Morling]

Hi all,

I'm looking for some input on an idea I got regarding group translation.

When discussing the issue [1] we agreed that the groups to be converted
should be specified with a new annotation instead of directly within
@Valid. So that's what we have right now:

public class User {

  @Valid
  @ConvertGroup(from = Default.class, to = BasicContact.class)
  private final Contact contact = new Contact();
}

IIRC the primary reason was that this new annotation could be re-used in
other places. IMO having a separate annotation is the right way, but WDYT
about specifying this annotation within instead of next to @Valid:

  @Valid(conversions=
    @ConvertGroup(from = Default.class, to = BasicContact.class
  )
  private final Contact contact = new Contact();

This would still allow to reuse the annotation, but avoids situations where
@ConvertGroup is given without @Valid. It also makes very clear what's
subject of the conversion (which might not be that obvious if the given
element hosts some more annotations).

On the down-side the "inner" annotation syntax is not that elegant,
although it's actually shorter when specifying multiple conversions:

  @Valid(conversions={
    @ConvertGroup(from = Default.class, to = BasicContact.class),
    @ConvertGroup(from = Full.class, to = FullContact.class)
  })
  private final Contact contact = new Contact();

vs.

  @Valid
  @ConvertGroup.List({
    @ConvertGroup(from = Default.class, to = BasicContact.class),
    @ConvertGroup(from = Full.class, to = FullContact.class)
  })
  private final Contact contact = new Contact();

This could be further mitigated by naming the attribute "value", although
I'm a bit shy of allocating that default attribute.

If we already discussed (and rejected) this particular approach, please
ignore this mail, otherwise any feedback is appreciated :)

--Gunnar

[1] https://hibernate.onjira.com/browse/BVAL-208
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