John,
Thanks, there's several interesting things here.
On 25/11/2011 18:04, John D. Ament wrote:
> Nigel,
>
> Sorry, should have read my message a bit more
> "plain objects" not plan objects; e.g. Strings, byte[]'s, Streams. Rather than needing to create a JMS specific
> domain object.
>
> MessageBuilder/QueueBuilder/TopicBuilder would replace something like MessageProducer/MessageConsumer and provide all
> APIs to the application to send and receive messages. We'd have to define the full API set, but what I current have
> is here:
>
> https://github.com/seam/jms/blob/develop/api/src/main/java/org/jboss/seam/jms/QueueBuilder.java
> https://github.com/seam/jms/blob/develop/api/src/main/java/org/jboss/seam/jms/TopicBuilder.java
>
> One thing we'll need to figure out is if we want to support this based on destination type or inspecific.
>
> Here's one example. Sending a Text message as a String.
>
> https://github.com/paulbakker/ducttape/blob/master/src/main/java/ducttape/managers/SmsNotifier.java
>
> In this example, we inject a basic topic builder (current codebase uses a default ConnectionFactory only), tell it to
> connect to a topic, and then send a TextMessage based on the input String.
> Here's a similar example using QueueBuilder:
>
> @Resource("jms/OrderQueue) Destination d;
> @Resource("jms/ConnectionFactory") ConnectionFactory cf;
> @Inject QueueBuilder queueBuilder;
>
> Serializable order = new Order(orderId);
> queueBuilder.connectionFactory(cf).destination(d).sendObject(order);
OK. Let's rewrite that with each method call on a separate line to help us understand it:
// fields
@Resource("jms/OrderQueue)
Destination orderQueue;
@Resource("jms/ConnectionFactory")
ConnectionFactory connectionFactory;
public void someMethod(
QueueBuilder queueBuilder = // omitted - is this just a no-arg constructor?
// set the connection factory
queueBuilder.connectionFactory(connectionFactory)l
// set the destination
queueBuilder.destination(orderQueue);
// sent the payload
Serializable order = new Order(orderId);
queueBuilder.sendObject(order);
I think there are three distinct innovations here:
1. You're merging the connection, session, and producer
2. You're using an API style that allows you to assemble a sequence of method calls on one line
3. The application is sending the payload directly without constructing a javax.jms.Message
Let me consider these separately:
*Innovation #1: merging the connection, session, and producer*
I think we're in agreement here:: this is consistent with the proposals I was discussing with Clebert a couple of weeks
ago. I think we can indeed merge the connection, session, and producer. Furthermore, as you may remember me explaining,
I think we can merge connection, session and async consumer, but we need to retain a separate object for sync consumption.
However I see no reason to need separate classes for queues and topics - this would be reversing the "domain
unification" of JMS 1.1.
I'm currently working up my ideas on this, but the trivial sending case would look like this
@Resource(lookup = "jms/connectionFactory")
ConnectionFactory connectionFactory;
@Resource(lookup="jms/inboundQueue")
Queue inboundQueue;
public void javaEESender() throws JMSException {
MessagingContext messagingContext = connectionFactory.createMessagingContext();
TextMessage textMessage = messagingContext.createTextMessage("Hello world");
messagingContext.send(inboundQueue,textMessage);
messagingContext.close();
}
The above is without CDI. I think it's important we have a simple API for non-CDI cases. However I envisage we could use
CDI to allow MessagingContexts to be injected directly, which would also take case of the close() method.
My suggestion is to pass in the destination as an argument to the send() method, whereas your suggestion it to set this
using a setter method. My feeling is that as the MessagingContext /QueueBuilder object would hold a connection, it is
relatively expensive, so we might want to reuse it with multiple destinations which means it's best to pass the
destination in as an argument. We don't want to force users to create two connections so they can write to two destinations.
My example above doesn't address the idea of sending the payload directly. That's something I'd like to change. See my
comment later.
Note that we can only merge connection and session for Java EE applications. In Java SE applications we need to retain
the ability to use multiple threads with a connection. I'm looking for an API which supports both modes without looking
too inconsistent. My idea is to provide ConnectionFactory.createMessagingContext() for Java EE users, and
Connection.createMessagingContext() for Java SE users who want multiple threads per connection.
*2. You're using an API style that allows you to assemble a cascade of method calls on one line*
As I said, I think this is just a matter of API style. Does this pattern have a name in Java? (It reminds me of method
cascading in Smalltalk).
Personally I would prefer a "setter" method to follow the standard Javadoc convention.
*3. The application is sending the payload directly without constructing a javax.jms.Message*
This is a big area which I haven't really got my head round yet, especially after the suggestions that were made to me
last week. I agree we should try to define an API which makes this possible. Whether we use my MessagingContext idea or
your QueueBuilder idea, the issues around sending and receiving object paylloads are the same.
I think we need to be clear what our goals are for this: I think it is more than just avoiding another intermediate
object. Users need to be able to plug their own converters (e.g. to convert an XML object type to a TextMessage,
ObjectMessage or ByteArray, whichever they prefer). Users also need to be able to construct a TextMessage by writing to
a Stream. Vendors need to continue to be able to handle very large messages efficiently. There are probably other
requirements as well. I'm not sure exactly what we need here and need to think about this a bit more before I can make
any useful comments.
Nigel
>
> John
>
>
> On Fri, Nov 25, 2011 at 12:41 PM, Nigel Deakin <nigel.deakin_at_oracle.com <mailto:nigel.deakin_at_oracle.com>> wrote:
>
> John,
>
> Thank you for the ideas.
>
> What is the purpose of MessageBuilder, TopicBuilder or QueueBuilder objects? Are these standard interfaces
> implemented by the JMS provider? What methods would they have?
>
> What's a "plan object"?
>
> Can you give a few examples of what the application code would look like?
>
> Nigel
>
>
> On 24/11/2011 00:06, John D. Ament wrote:
>> All,
>>
>> I wanted to propose a possible solution to this issue. I had previously not wanted to propose it since I wanted
>> to avoid new APIs to solve the issue. Its clear though that we need to have a new API to manage CDI
>> capabilities. I want to respond specifically to Nigel's comments from Devoxx separately, so that will come shortly.
>>
>> The idea is to provide a simple builder API for working with messages, both sending and receiving. I've thrown
>> around in my head a few ideas, such as MessageBuilder, TopicBuilder or QueueBuilder. I would break the interface
>> into sets of methods:
>>
>> 1. Set of methods responsible for configuring the builder.
>> 2. Set of methods responsible for creating messages from the builder.
>> 3. Set of methods responsible for sending messages and plan objects (not necessarily POJOs?) to destinations.
>>
>> For the first part, we would introduce methods for setting the connection factory, transactionality and
>> acknowledge mode. I would not include destinations here, since I would like to be able to connect to multiple
>> destinations.
>>
>> For the second group, I would create overloaded methods javax.jms.Message newMessage(X param) where X could be
>> one of Serializable, String, Map<T,R>, byte[], char[], Stream, etc. The returned type would be the correctly
>> typed method.
>>
>> For the third group, I would add similar methods for sendXMessage(X param), mostly for readability. These would
>> match up to each of the message types. In addition, we would support a send that takes a Message object.
>>
>> So here's how all of this correlates with CDI..
>>
>> You should be able to inject this builder object (or perhaps a builder factory) to your application. The
>> injection should always be a blank slate. In addition, you should be able to leverage reusability of code to
>> make your own customer builder. Let's suppose the following injection point...
>>
>> @Inject MessageBuilder builder;
>>
>> Then let's say you want to map the qualifier @EnterpriseSystem to have the connection factory found at
>> jms/Enterprise and set transacted to true, you should be able to handle that with CDI:
>>
>> @Inject MessageBuilder builder;
>>
>> @Resource(mappedName="jms/Enterprise")
>> private ConnectionFactory cf;
>>
>> @Produces
>> @EnterpriseSystem
>> public MessageBuilder createEnterpriseBuilder() {
>> return builder.connectionFactory(cf).transacted();
>> }
>>
>> So that when you did
>>
>> @Inject @EnterpriseSystem MessageBuilder builder;
>>
>>
>> So basically, JMS would expose an interface (or maybe more than one?) that handled injectable components. They
>> would not be bound to a connection factory at the creation level, but instead be configured by the application
>> developer. We allow for DRY support but put the ownership on the application developer.
>>
>> I hope this is clear enough for everyone, though I'd love for feedback.
>>
>> John
>>
>>
>> On Wed, Nov 23, 2011 at 7:37 AM, Pete Muir <pmuir_at_bleepbleep.org.uk <mailto:pmuir_at_bleepbleep.org.uk>> wrote:
>>
>> I spent some time looking at the DI problem that Nigel, Reza and Siva kindly explained to me at JavaOne. I
>> can't find a good way to support DI cleanly with the current object structure in JMS.
>>
>> Having spent a long time looking at DI, I would also highlight that using DI to fix an API is normally likely
>> to fail. It's a much better idea to fix the underlying API to accurately reflect the use cases that people
>> are commonly trying to solve, whilst still not making those other use cases impossible!
>>
>> So I would just like to fully support Clebert's approach here!
>>
>> On 22 Oct 2011, at 01:54, Clebert Suconic wrote:
>>
>> > Maybe that's a crazy idea. What if we took a totally new approach?
>> > Why do we still need connections sessions consumers and producers?
>> >
>> > What if we only had producers and consumers?
>> >
>> > You could maybe have producer extending AbstractSession and have commit, rollback... Etc
>> >
>> > The issue with annotations would be gone if we take an approach like that.
>> >
>> >
>> > Consider this a brain storm please. Don't flame me if that's a crazy idea. Especially that I'm writing this
>> in a Friday through the iPhone while drinking some wine :)
>> >
>> > Have a nice weekend.
>> > Sent from my iPhone
>> >
>> > On Oct 21, 2011, at 7:39 PM, Reza Rahman <reza_rahman_at_lycos.com <mailto:reza_rahman_at_lycos.com>> wrote:
>> >
>> >> It's a point I made before. If we leave things be on this for JMS 2, it gives projects/products like Seam
>> 3 JMS and Resin room to evolve further to bring about proven/mature solutions that real-world customers use
>> successfully in significant numbers. Currently, Seam 3 JMS is still in beta and Resin has a design and no
>> implementation yet. I think that's the real underlying problem we have rather than any fundamental usability
>> issue with what we need to do.
>> >>
>> >>
>> >> On 10/21/2011 7:48 AM, Nigel Deakin wrote:
>> >>> On 21/10/2011 03:12, Reza Rahman wrote:
>> >>>> Not to put too negative of a spin on this, but I don't think it would be terrible for non-standard
>> solutions in this problem space to evolve a bit more.
>> >>>
>> >>> There are rather too many negatives in that sentence for me to understand what you mean. Can you say a
>> bit more?
>> >>>
>> >>> Nigel
>> >>>
>> >>>>
>> >>>> That being said, we should still give this an honest try I think...
>> >>>>
>> >>>> On 10/19/2011 7:24 AM, Nigel Deakin wrote:
>> >>>>> Dear All,
>> >>>>>
>> >>>>> It's time for an update on progress on proposals to allow the injection of JMS objects into Java EE and
>> Java SE applications.
>> >>>>>
>> >>>>> The last update you had from me on his subject was on 7th September, when I circulated minutes from a
>> call I had with EG members Reza (Rahman) and John (Ament) to discuss John's AtInject proposals which were
>> circulated earlier.
>> >>>>>
>> >>>>> Since then Reza, John and I have had one or two further calls and extensive email correspondence. I
>> wrote a new document, based on the ideas in John's, which attempted to define a set of annotations which
>> could be used to inject JMS objects into applications. An updated version of this document is attached to
>> this message. It lists a fairly complete set of possible annotations to inject almost all JMS objects, but it
>> leaves a number of important issues unresolved, and until we can resolve these issues this document is simply
>> a statement of desire rather than a realistic practical proposal.
>> >>>>>
>> >>>>> The unresolved issues are listed in the document, but in summary, the main ones are
>> >>>>> * The relationship between injected objects
>> >>>>> * Avoiding repetition on annotations
>> >>>>> * Injected objects cannot be local variables
>> >>>>> * Scope of injected variables
>> >>>>> * Java SE support
>> >>>>>
>> >>>>> It is important to appreciate that if we can't resolve these issues then we will probably need to
>> abandon the document and start again.
>> >>>>>
>> >>>>> When I was at JavaOne earlier this month Reza and I had a meeting with Pete Muir, spec lead for CDI
>> (Contexts and Dependency Injection). He offered to work with us to see whether it would be possible to
>> achieve what we wanted in a reasonably standard manner using CDI - either the existing version or a future
>> version.
>> >>>>>
>> >>>>> Since it's been a few weeks since I gave the full expert group (and user list) an update on this,
>> please do feel free to ask questions about the attached document, make comments, or raise issues. Also, if
>> you think you have ideas on how to resolve the unresolved issues please say so!
>> >>>>>
>> >>>>> Thanks,
>> >>>>>
>> >>>>> Nigel
>> >>>>>
>> >>>>>
>> >>>>>
>> >>>>>
>> >>>>> -----
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>> >>>>
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>> >>
>>
>>
>