Enhanced method parameter validation: Proposal

eerriicc · **Joined:** Fri Mar 12, 2010 9:09 am **Posts:** 3

Hi

I'm rewriting our validation framework to Hibernate Validator. In general, I'm very happy with it, but there's one feature which I really miss.
You see, often a method parameter is actually the same as a property within a class, which already contains validation annotations.

Let's say you have a User class which contains an ID:

Code:

@Nonnull
@Range(min = 1, max = 9999)
// And some other validations
private Integer id;

And then you have a method which finds the user:

Code:

public User findUser(Integer id) { ... }

Using the method validation, you can of course specify:

Code:

public User findUser(@Nonnull @Range(min = 1, max = 9999) Integer id) { ... }

But that's a violation of the DRY principle, since the validation already exists in the User class.
That's why in our previous validation framework we had the annotation @ValidProperty. It assumes that the parameter's name is identical to the property of the specified class and then uses that property's validation.

For instance:

Code:

public User findUser(@ValidProperty(User.class) Integer id) { ... }

Of course, it should be possible to use a different parameter name, like:

Code:

public User findUser(@ValidProperty(value=User.class, property="id") Integer userID) { ... }

What do you think?

Gunnar · **Joined:** Sat Jan 24, 2009 12:46 pm **Posts:** 388

Hi,

I think this is an interesting feature which surely would be useful. Would you mind creating an issue in our JIRA (https://hibernate.onjira.com/browse/HV) for this?

Regarding matching parameter names with property/field names, one would have to define a way for specifying parameter names, though. Currently there is no way to access parameter names at runtime in Java (likely this will be possible in Java 8). How did you solve that problem for your @ValidProperty annotation?

What one surely could do as a first step, is to propagate field/property constraints to the corresponding setter method.

Note that as a workaround you could also create specific types for your attributes (e.g. UserId) which then wraps the actual attribute (e.g. id) and specifies all the required constraints for this attribute. When using this wrapper type, it can be validated using the @Valid annotation, which works on fields/properties but also for method parameters.

--Gunnar

eerriicc · **Joined:** Fri Mar 12, 2010 9:09 am **Posts:** 3

Gunnar wrote:

Hi,
I think this is an interesting feature which surely would be useful. Would you mind creating an issue in our JIRA (https://hibernate.onjira.com/browse/HV) for this?

Thanks for the reply! I've now created https://hibernate.onjira.com/browse/HV-686 - feel free to edit if something is not clear enough!

Gunnar · **Joined:** Sat Jan 24, 2009 12:46 pm **Posts:** 388

Cool, thanks for reporting the feature request.

--Gunnar