@NotEmpty annotation doesn't work on a collection

Support
#1

Hi,

I’m trying to validate an entity before saving, I need to check if a collection is not empty. I use @NotEmpty annotation on the field, but I still can save the object with an empty collection. However, @NotNull annotation on simple fields works perfectly. What could be the reason?

//...
public class Sale extends AbstractDocument {

    @NotNull //works well
    @JoinColumn(name = "COMPANY_ID")
    @OneToOne(fetch = FetchType.LAZY)
    private Company company;
//...
    @NotEmpty // Ignored - why?
    @OnDelete(DeletePolicy.CASCADE)
    @Composition
    @OneToMany(mappedBy = "sale")
    private Set<SaleProduct> saleProducts;
//...
}

I’ve also tried to use a custom validator, as described here https://docs.jmix.io/jmix/ui/screens/validation.html
but the method isValid() of my validator is never reached, too

#2

Hi @vadim.vainshtein
Thank you for reporting the problem.
Created issue. We’ll find out what we can do.

As for the “custom validator”, could you explain what you have tried?

#3

Hi Konstantin,
Thank you for your reply. Here is what I’ve tried:

I have an annotation to mark the required field:

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
@Constraint(validatedBy = NotEmptySetValidator.class)
public @interface NotEmptySet {
    String message() default "empty set";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};
}

and a validator class:

public class NotEmptySetValidator implements ConstraintValidator<NotEmptySet, Collection<?>> {

    @Override
    public boolean isValid(Collection<?> value, ConstraintValidatorContext context) {
        return !(value == null || value.isEmpty()); // never reached
    }
}

and I mark the field in my class

    @NotEmptySet
    @OnDelete(DeletePolicy.CASCADE)
    @Composition
    @OneToMany(mappedBy = "sale")
    private Set<SaleProduct> saleProducts;
#4

I believe the documentation says about automatic cross-field validation in edit screens if the entity class has a custom annotation with UiCrossFieldChecks group. It’s quite different from what you did.

#5

Yes, that’s what I realized after more careful reading. So still searching for a convenient way to do collection validation. At the moment I have my annotation on collections, and I’m checking them in overrided validateScreen(). But a problem comes when a component is disabled. By default Jmix doesn’t validate disabled components, and I would like to have this behavior on my validation, too. But I haven’t found any good solution for it yet.

#6

What if you just subscribe to the edit screen’s ValidationEvent?

@Subscribe
public void onValidation(ValidationEvent event) {
    if (stepsDc.getItems().isEmpty()) {
        ValidationErrors errors = new ValidationErrors();
        errors.add("Collection is empty");
        event.addErrors(errors);
    }
}
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#7

Oh, thank you, that is perhaps the best choice for now, I’ll use it! However, I have several similar screens that all inherit from one abstract screen, and I would like to have a really simple one-line method of marking a collection as required. The only thing I can invent is to have a reference to the collection in the superclass and to set it in every inheritor if needed… Not the prittiest idea, but better than nothing.

#8

Agree, we’ll try to make it in the issue I mentioned above.

1 Like