code: @Override
    public <T extends ConstraintValidator<?, ?>> T getInstance(final Class<T> key) {
      throw new UnsupportedOperationException("GWT does not support "
          + ConstraintValidatorFactory.class.getName() + " use GWT.create instead");
    }
docs: Always throws {@link UnsupportedOperationException}.
  
  @throws UnsupportedOperationException unsupported on gwt