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From: Michael Gentry <mgentry@masslight.net>
Date: Wed, 10 Mar 2010 08:32:31 -0500
Message-ID: <5adb61291003100532v30b86378m785f891516101f21@mail.gmail.com>
Subject: Re: Automated Validation of Attributes
To: dev@cayenne.apache.org
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Part of this would depend on your UI, too.  If you are using Tapestry
5, for example, it has similar validation built in.  Say you have a
text field with an id=3DfirstName, T5 will invoke (if present)
onValidateFromFirstName(String newFirstName) for you before ever
calling the setter.  If you throw an exception out of that, T5 will
know not to call the setter.  Once you've gone past that logic (which
would be the case you mention) it is a bit too late ...

Not sure if that made sense (I'm still waking up), but I hope so.  :-)

mrg


On Tue, Mar 9, 2010 at 10:42 PM, Andrew Lindesay <apl@lindesay.co.nz> wrote=
:
> Hello;
>
> As you may know, WebObjects/EOF has the protocol;
>
> =A0 =A0 =A0 =A0NSValidation
>
> Specifically, this protocol implements the following two methods;
>
> =A0 =A0 =A0 =A0Object validateTakeValueForKeyPath(Object value, String ke=
yPath)
> =A0 =A0 =A0 =A0Object validateValueForKey(Object value, String key)
>
> The effect is that when a client tries to write a property "foo", it will=
 ultimately try to invoke;
>
> =A0 =A0 =A0 =A0Object validateFoo(Object value) throws NSValidation.Valid=
ationException
>
> ...before...
>
> =A0 =A0 =A0 =A0setFoo(Object value)
>
> ...in order to either "repair" the value before assigning or to throw an =
exception. =A0This is very handy from the user-interface perspective. =A0Fo=
r each attribute of an entity, this technique is also automatically used in=
 the case of "validateForSave()" which means that aside from inter-attribut=
e validation, per-attribute validations can be implemented just once.
>
> To provide this same behaviour to Cayenne, I would like to put forward th=
e idea to implement something similar;
>
> =A0 =A0 =A0 =A0validatedWriteProperty(ValidationResult vr, String propNam=
e, Object value)
> =A0 =A0 =A0 =A0validatedWriteNestedProperty(ValidationResult vr, String p=
ropName, Object value)
>
> This would use (cached) reflection to look for a "validate" method and fi=
re that before writing the property. =A0For each attribute of a DataObject'=
s entity, these methods would be fired from;
>
> =A0 =A0 =A0 =A0void validateForSave(ValidationResult validationResult)
>
> Does this make sense in the context of Cayenne?
>
> Regards;
>
> ___
> Andrew Lindesay
> www.lindesay.co.nz
>
>