Hello WebSocket experts,
Here is the CDI/WebSocket issue I mentioned. The basic question that needs answering is what is the CDI Scope of a WebSocket endpoint ?
There seems to be two likely approaches: one where the request scope extends to the lifetime of a websocket connection. Sort of like how the request scope extends to async servlet sessions. Or one where WebSocket connections have their own potentially new scope.
But please read through this email from Bill Shannon (below) for a much fuller analysis and send your thoughts or suggestions,
Thanks,
- Danny
From Bill:
Experts,
An issue has come up about the definition of the CDI request scope and how
it applies to Web Sockets applications. The issue is reported here:
https://issues.jboss.org/browse/CDI-370
We're trying to decide whether this is a simple oversight that could be
corrected with an errata to the existing spec(s), or whether it's a missing
requirement that would require a new revision of the spec(s). Since this
involves the interaction of three specs, I'm starting the conversation here.
Here's the definition of when a request scope is active and when it is destroyed:
> The request scope is active:
>
> - during the service() method of any servlet in the web
> application, during the doFilter() method of any servlet filter and
> when the container calls any ServletRequestListener or AsyncListener,
> - during any Java EE web service invocation,
> - during any remote method invocation of any EJB, during any
> asynchronous method invocation of any EJB, during any call to an EJB
> timeout method and during message delivery to any EJB message-driven
> bean, and
> - during any message delivery to a MessageListener for a JMS
> topic or queue obtained from the Java EE component environment.
>
> The request context is destroyed:
>
> - at the end of the servlet request, after the service() method, all
> doFilter() methods, and all requestDestroyed() and onComplete()
> notifications return,
> - after the web service invocation completes,
> - after the EJB remote method invocation, asynchronous method invocation,
> timeout or message delivery completes, or
> - after the message delivery to the MessageListener completes.
It would be easy to "fix" the first bullet in each list above by saying
"oops, we forgot to include the work done by a protocol handler in
Servlet 3.1". Since all this other work done by Servlet applications
is part of the same request scope, adding the work done by protocol
handlers would make sense.
But, we have to decide if that's the fix we want.
Adding bullet items to each list to cover specific Web Socket operations
might be more what people are expecting, resulting in a request scope for
Web Sockets that's "smaller" than the request scope for the corresponding
http request. Even if we did that, we would still need to define clearly
whether or not a request scope is active during any arbitrary protocol
handler operation (not just Web Socket protocol handlers). Defining it
for Web Sockets but not defining it for protocol handlers in general might
be acceptable. Defining it one way for Web Sockets and a different way
for other protocol handlers would not be acceptable.
Should we fix this as an errata by saying that obviously protocol handler
operations should've been included in those lists of Servlet operations?
Or should we add items to each list to cover specifically Web Socket
operations? (In which case what do we say about protocol handlers in
general?) This would clearly require a new version of either the CDI
spec or the Web Sockets spec.
If we defined all Web Socket operations for a single http request to be
part of the same request scope (the "errata" approach), we could later
define a "message" scope or something similar to cover individual Web Socket
operations.
Let us know what you think.
Bill
--
<http://www.oracle.com> *Danny Coward *
Java EE
Oracle Corporation