Constraint @Length acts differently on Seam vs. Hibernate

[bartj07]

I'm using a @Length(min="2",max="5") constraint on a String property.  The inputText tag is required="false".  Upon submit, no error is reported on the UI, but when it's persisted it throws a validation exception.

My goal is to allow this field to be empty, but if they user fills it in, it should be between 2-5 characters.  Is there any way to do this with the standard annotations?

[admin.admin.email.tld]

you need to use <s:validate> or <s:validateAll> in your xhtml to trigger the hibernate validator(s) on the client-side as well.  are you doing that?

[bartj07]

Yup, my validation stuff works fine except for this case.  The problem is that it validates on the ui how I want, but not at persist-time. 
Specifically:

1) nothing filled in, doesn't throw validation error (required="false")

2) filled in, but below or above min and max, throws validation error

3) filled in, and between min and max, doesn't throw validation error

At persist-time, 1) throws an error.

[pmuir]

This is a mismatch between JSF and Hibernate validator, JSF sets an empty value as an empty String, not as null (which would pass the validation). Your best bet is to either write a custom length validator that allows this, or write some logic in your backing bean.

[epbernard]

Pete, you mean when the string is "", Seam (JSF really) does not run the validator? but still JSF place the value in the domain model?

[pmuir]

Exactly.

Also, if the field is empty in a JSF/facelet page, "" is set on the model, not null.

[christian.bauer]

Yes, this is a big bug in JSF. I have a few TODO curses in my source in places where I translate from "" to null. This should be fixed in JSF 2.0, Pete.

[epbernard]

I agree with Christian. This behavior is just leaking a web form presentation limitations into the rest of the application.
null is a much more sensible value.

[pmuir]

Ok, I will raise it with the JSF EG.