[cdi-dev] Recap of Context Management (CDI-30) hangout meeting

[Martin Kouba]

Dne 29.9.2016 v 12:59 Mark Struberg napsal(a):
> Martins argument with Quartz is a good one.
>
>
> Having 2 different ways to do the same thing might be making things too complicated. You also have to think about what happens if a user or libraries would mix the 2 approaches?

That's a good point. But I think it should be ok to state that 
activate() is no-op if the request context is already active (and the 
same for interceptor). I.e. both the interceptor and the 
RequestContextControl bean should perform the check described below.

>
> So my vote is for the programmatic approach.
>
>
> Oh and while we are at it:
> If we introduce some 'RequestContextControl' bean, should it also contain a isActive() method? Otherwise we might get into troubles with nesting such code.
> Of course it is possible by code like
>
>
> try {
>   beanManager.getContext(RequestScoped.class);
>   // request context is active
> }
>
> catch (ContextNotActiveException cnae) {
>   // request context is not active
>   // start it etc.
>
> }
>
>
> But that seems a bit heavyweight, isn't?
>
> LieGrue,
> strub
>
>
>
> On Thursday, 29 September 2016, 11:58, Antoine Sabot-Durand <antoine at sabot-durand.net> wrote:
>
>
>>
>>
>> That's also my choice:
>> We should provide 2) for advance usage and consistency sake if we go for Session context control later AND we should provide 1) for an easy usage of this feature.
>>
>>
>> A well written JavaDoc should prevent confusion between both approach.
>>
>>
>> Antoine
>>
>> On Thu, Sep 29, 2016 at 11:46 AM Martin Kouba <mkouba at redhat.com> wrote:
>>
>>
>>> Dne 29.9.2016 v 11:16 Antoine Sabot-Durand napsal(a):
>>>> Hi all,
>>>>
>>>> Just to sum up what was said during our Tuesday Hangout meeting. For
>>>> those who were present feel free to correct or amend this.
>>>>
>>>> Controlling Request Context is something rather easy (because it's
>>>> linked to one thread) while Session Context is far less obvious (used
>>>> across multiple threads) so providing a generic solution to deal with
>>>> their control seems quite complicated.
>>>> That's why we decided to start addressing the Request Context control
>>>> first and if we fell happy with that, continue the work on the Session
>>>> Context.
>>>>
>>>> Public API to control the request context could be design in 2 different
>>>> ways:
>>>> 1) provide an interceptor to activate request context during the
>>>> intercepted method invocation
>>>
>>> This approach is also not always usable in some integration use cases
>>> where the request cannot be simply "wrapped in a single method call".
>>>
>>> For instance, in Quartz scheduler you can register a job listener with
>>> methods jobToBeExecuted(), jobExecutionVetoed() and jobWasExecuted() -
>>> here the approach 2) would make sense. On the other hand, you could
>>> implement a JobFactory so that Job instances are beans (or at least
>>> instances obtained and injected from an InjectionTarget) and simply
>>> associate interceptor binding for its execute() method.
>>>
>>>> 2) provide a programmatic API accessible thru a bean (like the
>>>> Conversation bean)
>>>>
>>>> First solution is probably the easiest way for end user (to avoid not
>>>> ended context), but if we go for controlling Session Scope we won't be
>>>> able to provide a simple interceptor for it and will design something
>>>> like solution 2 for it.
>>>>
>>>> So the question is should we go for 1 or 2 or both (with a risk of
>>>> confusion) ?
>>>
>>> I think that both ways are legal and make sense.
>>>
>>>>
>>>> Thanks for your feedback
>>>>
>>>> Antoine
>>>>
>>>>
>>>>
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>>>
>>
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