Predicates as Constraints

[Niclas Hedhman]

Gang,
ZEST-36...

I think it makes sense to get rid of the Constraint interface and use the
Predicate instead.
And at the same time support a ConstraintFactory concept, where the
Predicate can be created by a factory, to support the CompositeConstraint
concept that exists (I didn't know that).

So, something like this;

public interface Customer
{
    Property<String> name();

    @Age
    Property<Integer> age();
}

@ConstraintDeclaration
@Retention( RUNTIME )
@Constraints( AgePredicate.class )
public @interface Age
{
    int min() default 18;
    int max() default 95;
}

public static class AgePredicate
    implements Predicate<Integer>
{
    private Age range;

    @Override
    public boolean test( Integer argument )
    {
        return argument > range.min() && argument < range.max();
    }
}

I will think a little bit more about the ConstrainFactory, but it should
probably get access to a bit more than just the Annotation.

To make the codebase lean, I would like to remove the Constraint variant
completely, although @Constraints remain as previously.

WDYT?

Cheers
-- 
Niclas Hedhman, Software Developer
http://zest.apache.org - New Energy for Java