[JMS_SPEC-116] Take advantage of EJB 3.2's RA improvement for MDBs Created: 12/Mar/13  Updated: 02/Sep/13

Status: Open
Project: jms-spec
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: New Feature Priority: Major
Reporter: John D. Ament Assignee: Unassigned
Resolution: Unresolved Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
is related to JMS_SPEC-134 Declarative Annotation Based JMS List... Open
Tags: jms21-forreview-major, messagedriven, ra


In a late change to the EJB 3.2 spec, a new feature around building MDBs without requiring method-level implementations has been added, specifically for use within the RA.

I am proposing that the JMS spec take advantage of this new feature in the following ways:

The description references this email thread from the EJB Spec: http://java.net/projects/ejb-spec/lists/jsr345-experts/archive/2013-03/message/49

1. Introduce a new interface "javax.jms.JMSMessageEndpoint" (or similar name) that can be used as a marker interface required by MessageEndpointFactory.getEndpointClass(). It shall have no methods, not extend any other interface but simply exist to be a marker that the given class will have its public methods exposed as potential targets for messages received by the RA.

2. Introduce a new annotation, or possibly several annotations, to represent the configuration available to these methods. I believe we should support something more fluid (e.g. compiler friendly) than the existing ActivationConfigProperty set.

3. Currently, the onMessage method is defined by looking for a method named "onMessage" that takes a "Message" object as an argument. This algorithm should be changed to also look for any instance of "JMSMessageEndpoint", find any method that is annotated as XXX (whatever is defined in 2) as a possible target, then depending on there being a match between that takes anything that derives from "Message" and only pass appropriate messages to it.

Some down sides:

1. The EG has already voted to not require an RA with every implementation.
2. This is a late change, so is the EJB equivalent.
3. Currently, MDB behavior and RA aren't necessarily defined within the JMS spec.

Comment by Nigel Deakin [ 12/Mar/13 ]

This interesting change comes too late to make any corresponding changes to JMS 2.0. I have added this issue to the list of issues which will be considered for JMS 2.1 and tagged it accordingly.

I'll also start a thread on the expert group to discuss this. Feel free to join in (or to contact me (Nigel) directly).

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