+1. I agree with the new proposal. It is less confusing to make a clear
distinction between "legacy" JMS MDBs and "new-style".
Josh Juneau
On Tue, Sep 8, 2015 at 6:29 AM, Nigel Deakin <nigel.deakin_at_oracle.com>
wrote:
> (This email refers to my proposals to improve JMS MDBs at
> <https://java.net/projects/jms-spec/pages/JMSListener2>
> https://java.net/projects/jms-spec/pages/JMSListener2)
>
> The next issue I'd like to discuss is the
>
> *Relationship between the old and new ways to define a JMS MDB *This
> boils down to the question "should the new annotations be allowed for MDBs
> that implement the javax.jms.MessageListener interface?"
>
> There are two possible cases we need to consider:
>
> - Allowing these new annotations to be used on the legacy onMessage
> method of a javax.jms.MessageListener
>
> Version 2
> <https://java.net/projects/jms-spec/pages/JMSListener2#Specifying_the_callback_method>
> proposed any of the new annotations could be specified. However the
> requirement that the @JMSListener always be specified could not apply
> since that would break existing MDBs.
>
>
> - Allowing these new annotations to be used to define additional
> callback methods (i.e. in addition to the onMessage method).
>
> Version 2
> <https://java.net/projects/jms-spec/pages/JMSListener2#Specifying_the_callback_method>
> proposed that this be allowed so long as the MDB also implemented the
> no-method javax.jms.JMSMessageDrivenBean marker interface.
>
> On reflection, I'm wondering whether this is introducing unnecessary
> complexity. It means that lots of additional use cases need to be defined
> in the spec, implemented, and tested, whilst bringing little benefits to
> users who can convert to a new-style JMS MDB easily enough.
>
> In addition, since we're seeking EJB spec changes to remove the need for
> the javax.jms.JMSMessageDrivenBean marker interface completely, it
> doesn't make any sense to introduce a requirement to use it here.
>
> I'm therefore wondering whether it would be better to make a clear
> distinction between "legacy" JMS MDBs and "new-style" JMS 2.1 MDBs. Here's
> what I'm suggesting:
>
> - Legacy JMS MDBs would implement javax.jms.MessageListener and be
> configured as they are now.
>
>
> - New-style MDBs would not implement javax.jms.MessageListener. They
> would use the new annotations to specify the callback methods. They would
> also implement the javax.jms.JMSMessageDrivenBean marker interface,
> though we're seeking EJB spec changes to remove the need for this.
>
>
> - If the new annotations were used on a MDB which implements
> javax.jms.MessageListener then deployment would fail. This would be a
> mandatory requirement on the application server or resource adapter.
>
> There are other options for combining these features, but I'm suggesting
> that keeping them separate will make things simpler.
>
> What do you think? is this better, or would you prefer the original
> proposal?
>
> Nigel
>