I was indeed primarily addressing Pete.
In terms of the conventional use of the JMS API, "auto-commit" probably best translates to thread-local or "method local" scope rather than "stateless" or "no scope" (keep in mind though, Spring JMS template is basically a "stateless" API)? That would maintain the session even in absence of a transaction to roughly what a JMS user would expect it to be (we might have to make it clear that only certain session types are legal when there is no JTA transaction - I'd have to think it through). I'll have to go back and look, but I think that's in fact what we did for Resin's JPA entity manager proxy (the fall-back was thread scope). Another option is to simply state that message context injection only works with JTA transactions (would probably be fine for Java EE use of JMS since it's primary seen as a transactional resource).
Feb 10, 2012 11:24:01 AM, jsr343-experts_at_jms-spec.java.net wrote:
===========================================
On 10/02/2012 15:53, reza_rahman_at_lycos.com wrote:
> Did the CDI EG transaction scope discussion go anywhere? If it is really needed, I can help drive that discussion (unless you think that discussion belongs somewhere else)?
(I presume you're asking Pete)
> The way I see it, in absence of a JTA transaction, the scope should behave in the equivalent of "auto-commit" in the DB world. In the component life-cycle world, I think this best translates to the EJB concept of "stateless".
I don't follow how a "scope" can be like auto-commit.
In the absence of a JTA transaction, the session will be non-transacted with either auto-ack or dupsok-ack mode. (This
is implied by the existing EJB spec and I have clarified this in a new section 10.3 of the JMS 2.0 spec). That's similar
to auto-commit.
But this is a separate issue from the scope (longevity) of the connection and session. That's about how long we want to
hold on to resources.
One other thing: even when there is no JTA transaction, a messagingContext (or rather its producer) cannot be stateless,
since it defines message order when sending messages. So
messagingContext.send(dest,message1);
messagingContext.send(dest,message2);
messagingContext.send(dest,message3);
messagingContext.send(dest,message4);
messagingContext.send(dest,message5);
would have different message ordering semantics if each messagingContext was actually a separate instance.
Nigel
>
> Feb 10, 2012 05:48:21 AM, pmuir_at_bleepbleep.org.uk wrote:
>
> ===========================================
>
> The underlying work that I worked on with Nigel would work fine with any scope (including a possible transaction scope).
>
> Nigel and I discussed whether a transaction scope would be sensible, but we were concerned that whilst it seemed like a good fit when there was a transaction running, the cases when there is no transaction, the semantics of the scope become messy.
>
> IMO the best thing is to produce a general transaction scope proposal that addresses edge cases. JMS could then pick this up if it wants.
>
> On 10 Feb 2012, at 04:10, Reza Rahman wrote:
>
>> This looks pretty good I think.
>>
>> Personally, I would have preferred the greater granularity of the transaction scope. However, I'll also acknowledge that it can be difficult to comprehend and most probably overkill. I do hope the request scope has a sensible definition in Java SE/non-web contexts. Similarly, I personally like the hierarchical model of the JMS 1.x API slightly better and feel it can be fit fairly nicely into a DI based solution. However, I'll acknowldge that the DI approach would not necessarily be very simple and most folks don't seem to have issues with a flatter "Spring JMS template" style messaging API.
>>
>> I suggest socializing the API with the larger community soon. I can certainly help if needed.
>>
>> On 2/8/2012 10:27 AM, Nigel Deakin wrote:
>>> I created this new issue a couple of days ago to allow us to track the injection of MessagingContext objects separately from the rest of the simplified API:
>>> http://java.net/jira/browse/JMS_SPEC-70
>>>
>>> Currently, the simplified API is in the Early Draft but the injection of MessagingContext objects is not. However if there is general agreement on what is proposed below I propose to include this in the Early Draft as well (since supporting this was the main reason for defining the simplified API):
>>>
>>> Any comments? (If you don't understand what I am proposing, please let me know either directly or via the list)
>>>
>>> If it's hard to read the text below, the same content may be found in the JIRA issue.
>>>
>>> I described the requirement as follows:
>>>
>>> --------------------------------------------------------
>>> The simplified API (JMS_SPEC-64) defines a single object, javax.jms.MessagingContext, which provides methods for sending and receiving messages.
>>>
>>> It is proposed that the JMS API define some standard annotations that can be used to inject MessagingContext objects into application code.
>>>
>>> * The injection point should allow the application define the two parameters needed to create a MessagingContext: JNDI name (of the connection factory) and sessionMode. Both should be optional with suitable defaults.
>>>
>>> * The implementation should ideally be implemented using CDI and have behaviour consistent with it. However this is not essential.
>>>
>>> * It must be possible to use injection in Java EE applications. It is desirable but not essential to be able to use injection in Java SE applications.
>>>
>>> * Injected MessagingContexts must have an appropriate scope and must be automatically closed when they fall out of scope.
>>> --------------------------------------------------------
>>>
>>> I've now drafted a new section for the JMS spec that defines how users will inject MessagingContext objects. I've added this text, and the proposed new annotation interfaces, to the JIRA issue:
>>> http://java.net/jira/browse/JMS_SPEC-70
>>>
>>> I've pasted the same text below. (To see the actual annotation definitions, see the JIRA issue).
>>>
>>> I'd like to thank Pete Muir, CDI spec lead, helping me define a mechanism for injecting MessagingContext objects which
>>> * Allow JNDI name and sessionMode to be specified in the injection point
>>> * Ensures injected objects are closed at the end of the request
>>> * Is consistent with CDI style
>>> * Is capable of being implemented
>>>
>>> I have a working prototype which implements this, based on a proposal from Pete, and which I'm happy to share.
>>>
>>> I'd also like to acknowledge the help I was given earlier by Reza (Rahman) and John (Ament).
>>>
>>> --------------------------------------------------------
>>>
>>> This section relates to application classes which run in the Java EE web, EJB or application client containers and which support injection. Section EE.5 of the Java EE specification lists the application classes that support injection.
>>>
>>> Applications may declare a field of type javax.jms.MessagingContext and annotate it with the javax.inject.Inject annotation:
>>>
>>> @Inject
>>> private MessagingContext context;
>>>
>>> The container will inject a MessagingContext. It will have request scope and will be automatically closed when the request ends. However, unlike a normal CDI request-scoped object, a separate MessagingContext instance will be injected for every injection point.
>>>
>>> The annotation javax.jms.JMSConnectionFactory may be used to specify the JNDI lookup name of the ConnectionFactory used to create the messaging context. For example:
>>>
>>> @Inject
>>> @JMSConnectionFactory("jms/connectionFactory")
>>> private MessagingContext context;
>>>
>>> If no lookup name is specified or the JMSConnectionFactory annotation is omitted then the platform default JMS connection factory will be used.
>>>
>>> The annotation javax.jms.JMSSessionMode may be used to specify the session mode of the messaging context:
>>>
>>> @Inject
>>> @JMSConnectionFactory("jms/connectionFactory")
>>> @JMSSessionMode(MessagingContext.AUTO_ACKNOWLEDGE)
>>> private MessagingContext context;
>>>
>>> The meaning and possible values of session mode are the same as for the ConnectionFactory method createMessagingContext(int sessionMode):
>>>
>>> * In the Java EE application client container, session mode may be set to any of MessagingContext.SESSION_TRANSACTED, MessagingContext.CLIENT_ACKNOWLEDGE, MessagingContext.AUTO_ACKNOWLEDGE or MessagingContext.DUPS_OK_ACKNOWLEDGE. If no session mode is specified or the JMSSessionMode annotation is omitted a session mode of MessagingContext.AUTO_ACKNOWLEDGE will be used.
>>>
>>> * In a Java EE web or EJB container, when there is an active JTA transaction in progress, session mode is ignored and the JMSSessionMode annotation is unnecessary.
>>>
>>> * In a Java EE web or EJB container, when there is no active JTA transaction in progress, session mode may be set to either of MessagingContext.AUTO_ACKNOWLEDGE or MessagingContext.DUPS_OK_ACKNOWLEDGE. If no session mode is specified or the JMSSessionMode annotation is omitted a session mode of MessagingContext.AUTO_ACKNOWLEDGE will be used.
>>>
>>> For more information about the use of session mode when creating a messaging context, see section 10.3 of the JMS 2.0 Early Draft, "Behaviour of JMS sessions in the Java EE web or EJB container" and the API documentation for the ConnectionFactory method createMessagingContext(int sessionMode).
>>>
>>> --------------------------------------------------------
>>>
>>> Here are three simple examples:
>>>
>>> 1. Sending a TextMessage in a Java EE web or EJB container.
>>>
>>> @Inject
>>> @JMSConnectionFactory("jms/connectionFactory")
>>> private MessagingContext messagingContext;
>>>
>>> @Resource(mappedName = "jms/inboundQueue")
>>> private Queue inboundQueue;
>>>
>>> public void sendMessageNew(String payload) {
>>> messagingContext.send(inboundQueue, payload);
>>> }
>>>
>>> 2. Receiving a message synchronously in a Java EE web or EJB container.
>>>
>>> @Inject
>>> @JMSConnectionFactory("jms/connectionFactory")
>>> private MessagingContext messagingContext;
>>>
>>> @Resource(lookup="jms/inboundQueue")
>>> Queue inboundQueue;
>>>
>>> public String receiveMessageNew() {
>>> SyncMessageConsumer syncMessageConsumer = messagingContext.createSyncConsumer(inboundQueue);
>>> return syncMessageConsumer.receivePayload(String.class);
>>> }
>>>
>>> 3. Receiving a message synchronously from a durable subscription in a Java EE web or EJB container.
>>>
>>> @Inject
>>> @JMSConnectionFactory("jms/connectionFactory2")
>>> private MessagingContext context;
>>>
>>> @Resource(lookup="jms/inboundTopic")
>>> Topic inboundTopic;
>>>
>>> public String receiveMessageNew() {
>>> SyncMessageConsumer syncMessageConsumer = context.createSyncDurableConsumer(inboundTopic, "mysub");
>>> return syncMessageConsumer.receivePayload(String.class);
>>> }
>>>
>>>
>>>
>>>
>>>
>>>
>>>
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>>>
>>>