[cdi-dev] New Servlet related scope - @UpgradeScoped (?)

Pavel Bucek pavel.bucek at oracle.com
Thu Dec 4 04:51:32 EST 2014

please see inline.

On 04/12/14 10:30, arjan tijms wrote:
> Hi there,
> On Thursday, December 4, 2014, Pavel Bucek <pavel.bucek at oracle.com 
> <mailto:pavel.bucek at oracle.com>> wrote:
>     Hello Arjan,
>     On 03/12/14 19:44, arjan tijms wrote:
>>     Hi,
>>     On Wednesday, December 3, 2014, Pavel Bucek
>>     <pavel.bucek at oracle.com
>>     <javascript:_e(%7B%7D,'cvml','pavel.bucek at oracle.com');>> wrote:
>>         Hi all,
>>         I'm trying to figure out how to solve issue in JSR 356 - Java
>>         API for
>>         WebSocket, related to CDI scope usable from WebSocket
>>         endpoints. Problem
>>         is, that "standard" scopes do not apply, because there is no
>>         @RequestScoped (http response is already sent), HttpSession
>>         does not
>>         need to be created and the rest does not seem to be
>>         applicable, ...
>>         I believe that CDI specification should define
>>         @UpgradeScoped, which
>>         would cover usages of HttpUpgradeHandler from Servlet API.
>>         (Similarly as
>>         it does for @RequestScoped, @SessionScoped, ... )
>>     Wouldn't it be a better option to have WebSocket define that
>>     scope, using CDI to implement it?
>     That is one possibility, but @UpgradeScoped would be more general
>     than just for WebSocket - it would apply for all HTTP/1.1+ Upgrade
>     applications.
> Okay, so in a more broader application than just WebSocket it could be 
> defined somewhere lower in the spec hierarchy. If it's specific to 
> HTTP upgrades as you mention, then Servlet may be the next candidate 
> to consider.

As you most likely already know, Servlet spec does not contain any scope 
definition (yet). The natural way for me is to add the new stuff 
somewhere near the "old" declaration, which would seem logical for all 
users. (please see below for comment to possible move of these 
declarations to Servlet spec).

>      In my eyes, it is something which was forgotten to do in Java EE
>     7 release, since HttpUpgradeHandler was introduced in it.
>     Also please note, that other Servlet related scopes are already in
>     CDI spec, so it seems like it belongs there more than anywhere else.
> But some of these may not actually belong there. They may have been 
> put there originally since as a new spec that had yet to be proven, 
> CDI could not right away ask other specs to support it.
> There are discussions going on to move some of the Servlet things from 
> CDI to Servlet.

Do you know about thread like that somewhere? (CDI / Servlet mailing 
list)? I'm for moving this to Servlet, since it seems like it should 
belong there, but current scope definitions are well established and 
known and deprecating/moving the @*Scoped declarations might not be 
perceived as positive change. Anyway, I'd like to joint that discussion 
to make sure that the new scope will be introduced.

>      This might have multiple reasons - for example, you can easily
>     define relationship between @UpgradeScoped and others, already
>     existing ones. In this sense, CDI specification now depends on
>     Servlet API (it references some of the classes defined in it), but
>     Servlet does not do that for CDI. I don't think that Servlet spec
>     should introduce similar dependency just because of new scope.
> There are plenty of other reasons too ;) For Servlet I expect the 
> dependencies to be optional. Servlet in a EE environment will then 
> provide scope X & Y, and producers for types Q & R, but it will 
> continue to run standalone without needing any CDI. In short, it 
> would provides things for CDI then but in its core wouldn't need CDI.
> Just my 2 cents ;)
Thanks! :-)

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