[bv-dev] Scopes support for custom constraint validators

[Gunnar Morling]

If I understand right, you need some kind of scope which lasts as long as
one validation call.

You could easily implement this yourself using a ThreadLocal object, either
in form of a custom CDI scope or - if you don't want to work with CDI -
using a ThreadLocal object directly within your code.

The only issue is that there is no hook/life cycle event or similar which
could be used to trigger the clean up this scope once validation is over.
For that purpose you could implement a proxy object for
javax.validation.Validator which delegates to the actual validator
implementation but handles the scope management.

--Gunnar




2013/6/17 Thang Le <thangmle at gmail.com>

> Hi all,
>
> I have done some research along the CDI support in BV 1.1. I agree that
> CDI as described in JSR-299 is a very powerful framework which possibly
> fulfills different needs for scopes of constraint validators. However, I
> feel reluctant to adopt such a complete CDI implementation into my project
> since this adoption is too much for a little gain. Beside scopes for
> constraint validators, all other features described in CDI are redundant
> for my need. Even if I use CDI implementation, I still have to write the
> scope for my constraint validators since there is no built-in scope that
> fits my need. Most of the existing scopes are tailored to use with
> web-beans. There is no built-in scope for object-graph validation scope
> which is what I need.
>
> After looking through CDI spec, I am not quite convinced that supporting
> scopes in Bean Validation should be done by CDI module. Since constraint
> validators are created by the bean validation module, would it be better
> that they should have different validation scopes which should also be
> managed by the bean validation module?
>
> Thang
>
> On Thu, Jun 13, 2013 at 9:29 AM, Thang Le <thangmle at gmail.com> wrote:
>
>> That's great! Let me take a look into this.
>>
>> Thanks,
>> Thang
>>
>>
>> On Thu, Jun 13, 2013 at 2:59 AM, Gunnar Morling <gunnar at hibernate.org>wrote:
>>
>>> Hi,
>>>
>>> As Gerhard is saying, BV 1.1 is integrated with CDI.
>>>
>>> So you could also implement your expensive operation in an application
>>> scoped bean which you @Inject into your constraint validator.
>>>
>>> For BV 1.0 there is also Seam Validation [1] (not actively maintained
>>> anymore, though). When using BV with Spring, there is DI support for
>>> validators as well. So I don't think this requires any addition to the BV
>>> spec.
>>>
>>> --Gunnar
>>>
>>> [1] http://seamframework.org/Seam3/ValidationModule
>>>
>>>
>>>
>>> 2013/6/12 Gerhard Petracek <gerhard.petracek at gmail.com>
>>>
>>>> hi thang,
>>>>
>>>> bv 1.1 allows to use cdi beans as constraint-validators.
>>>> (for bv 1.0 you can use add-ons like the bv module of [1] or [2].)
>>>>
>>>> -> you can use any scope you need.
>>>>
>>>> regards,
>>>> gerhard
>>>>
>>>> [1] http://myfaces.apache.org/extensions/cdi/
>>>> [2] http://deltaspike.apache.org
>>>>
>>>>
>>>>
>>>> 2013/6/12 Thang Le <thangmle at gmail.com>
>>>>
>>>>>  Hi all,
>>>>>
>>>>> I've come across a scenario which makes me think supporting different
>>>>> scopes for custom constraint validators would ease the task for writing
>>>>> efficient validation logic. Similar to Spring IoC, these scopes are
>>>>> prototype, session & singleton. Currently, the Bean Validation 1.1 spec
>>>>> suggests a 'prototype' scope should be used for all custom constraint
>>>>> validation classes. In my opinion, the 'session' (likely singleton as well)
>>>>> scope proves to be useful when a custom constraint validator needs to do
>>>>> the SAME  timing pre-processing logic before doing some actual validation
>>>>> logic on the current targeted object. In such cases, the developer would
>>>>> want to store the result of the pre-processing logic into an instance
>>>>> variable of the custom constraint validation class and reuse this result
>>>>> later when the constraint is executed again on different objects. Below is
>>>>> a specific use-case from my current project.
>>>>>
>>>>> The model I need to validate has a tree-like structure. In this model,
>>>>> each node can be a/an remote/access-point/cluster. I have a model builder
>>>>> which builds the model tree given a set of nodes. The builder then hands
>>>>> off this tree to the validator to validate it. I have some constraints
>>>>> which require to check the uniqueness of a certain property for a set of
>>>>> nodes (e.g: all access-points in the tree must have unique serial number).
>>>>> These constraints are written as custom constraints. I recognize these
>>>>> constraints follow the same pattern which is I need to traverse the tree to
>>>>> collect all required node and build a multimap out of the collected nodes
>>>>> and check for uniqueness using the key of the current targeted object. For
>>>>> above example, the custom constraint is a class constraint of access-point
>>>>> class. I need to collect all access-points in the tree, build a multimap of
>>>>> <serialNumber:access-point> pairs. Then I lookup from the map the
>>>>> collection of access-points based on the serial number of the access-point
>>>>> being validated. It would be beneficial if the multimap of
>>>>> <serialNumber:access-point> pairs can be stored in the custom validator so
>>>>> that I don't need to re-do this expensive task again when validating other
>>>>> access-points.
>>>>>
>>>>> There might be some reasons that you wouldn't want to support
>>>>> different scopes for custom constraint validator. However, I would think
>>>>> when it comes to writing a constraint for a bean in relation with other
>>>>> beans, such scopes become handy. Please let me know your thoughts on this
>>>>> feature.
>>>>>
>>>>> Thang
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> beanvalidation-dev mailing list
>>>>> beanvalidation-dev at lists.jboss.org
>>>>> https://lists.jboss.org/mailman/listinfo/beanvalidation-dev
>>>>>
>>>>
>>>>
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