Using script expressions for object validations

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

Hi all,

recently I built a constraint annotation that allows to use statements written in script languages such as Groovy for object validation (inspired by the @Assert annotation of the OVal framework).

Using this annotation, constraints referring to multiple attributes of a bean can easily be expressed, as in the following example:

Code:

@ScriptAssert(lang = "groovy", script = "_this.startDate.before(_this.endDate)")
public class CalendarEvent {

    private Date startDate;

    private Date endDate;

    //constructor, getters and setters ...

}

More information can be found in my web log at http://musingsofaprogrammingaddict.blog ... ation.html. I'd be happy on any feedback, ideas for improvement etc.

Gunnar

matt_foley · **Joined:** Tue Jul 21, 2009 2:57 pm **Posts:** 8

i implemented a class-level constraint with OGNL expressions. seemed like a universal kind of use-case. of course, i then realized that most of our constraints could be replaced with this alone.

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

There is also a JSR 223 compatible engine for OGNL, so the ScriptAssert annotation should work with OGNL as well (haven't tried it out, though). I think, I still would use custom class-level constraints in more complex cases, as they provide more compile-time safety.