Java Bean Validation: How do I specify multiple validation constraints of the same type but with different groups?

Question

I have multiple processes in which the bean properties must have different values. Example:

@Min( value=0, groups=ProcessA.class )
@Min( value=20, groups=ProcessB.class )
private int temperature;

Unfortunately the bean validation JSR 303 has not set @Repeatable on javax.validation.constraints.Min so this approach does not work. I found "Min.List" but without any doc about how to use it. Instead the official Oracle doc states at http://docs.oracle.com/javaee/7/api/javax/validation/constraints/class-use/Min.List.html

No usage of javax.validation.constraints.Min.List

So at moment this looks like a specification error?!?

The documentation also says "Defines several Min annotations on the same element.". So it looks exactly like what you want to do. Have you tried using it? What's the difficulty? — JB Nizet, Apr 07 '15 at 22:06
javac throws a compile error: Duplicate annotation of non-repeatable type @ Min. Only annotation types marked @Repeatable can be used multiple times at one target. — Jemolah, Apr 07 '15 at 22:19
That's what it says when you use `@Min` twice, as in the code you posted. And that's why you should use `@Min.List` instead, which is documented as "Defines several Min annotations on the same element.". What happens when you use `@Min.List`? — JB Nizet, Apr 07 '15 at 22:20
Interesting idea. Really. But I don't get any correct syntax for it. Writing @Min( value=0, groups=ProcessA.class ) results in: "The attribute groups is undefined for the annotation type Min.List" — Jemolah, Apr 07 '15 at 22:25
Min.List is specified as an internal interface of Min itself: @interface List { Min[] value(); } — Jemolah, Apr 07 '15 at 22:32

score 11 · Accepted Answer · answered Apr 07 '15 at 22:30

11

The syntax for Min.List, as for any other annotation taking an array of annotations as one of its attributes, is

@Min.List({ @Min(value = 0, groups = ProcessA.class),
            @Min(value = 20, groups = ProcessB.class) })

answered Apr 07 '15 at 22:30

JB Nizet

Thanks. That's it. Any idea why this is better than just having Min multiple times? At least it decreases readability. – Jemolah Apr 07 '15 at 22:35
4

Annotations are repeatable since Java 8. Bean validation was designed on Java 5 or 6. So this possibility didn't exist, hence the workaround of Min.List. If Bean Validation was designed now, Min.List would probably not exist. – JB Nizet Apr 07 '15 at 22:56
1

Good point. Thanks. I will make this an enhancement request to bean validation. – Jemolah Apr 08 '15 at 09:16

1 Answers1