[Stripes-users] Range checking validation

Hey Everyone,

It seems that one kind of validation that isn't currently provided by  
Stripes, but is quite common, is range checking.  E.g. check that a  
field value is between 1 and 100 etc.  I've punted on this before  
primarily because the restrictions annotation properties makes it  
hard to come up with a clean, universal solution to this.  My desire  
had been to make it possible to do range checking on any type that  
implements Comparable, not just on numbers.  This would include  
things like Strings, Dates etc.

The way I see it is that there are basically two alternatives.  The  
first would be to implement this just for numbers, and the annotation  
would be completely type-safe, e.g.:

@Validate(minvalue=0, maxvalue=120)
public long getAge() { ... }

The other option would be to implement it for any type that  
implements Comparable.  This would be significantly more complex, so  
I'd like to make sure that it's worthwhile before investing too much  
time in it.  In this case the validation might look like this:

@Validate(minvalue="1/1/1900")
public Date getBirthday() ...

@Validate(minvalue="0", maxvalue="120")
public long getAge() ...

Notice the quotes around the values in this case.  How I would see  
this working is that the quoted value would get converted to the same  
type as the property, using the Stripes type conversion system.  Then  
compareTo() would be used to ensure that the field value was greater  
than the minimum supplied, and less than the max supplied etc.  The  
downside to this approach is that it makes it possible to screw up  
the annotation and put junk in the min/maxvalue attributes.

I'd appreciate any feedback on this.  Is it worth adding the extra  
complexity of the second option?  I'm not worried about coding it in  
Stripes so much as making it easier for users of Stripes to run into  
errors.  Cheers,

-t


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