11 a.m.
On 27/08/2015 16:35, Romain Manni-Bucau wrote:
2015-08-27 17:31 GMT+02:00 Nigel Deakin <nigel.deakin(a)oracle.com
<mailto:nigel.deakin@oracle.com>>:
On 26/08/2015 10:16, Romain Manni-Bucau wrote:
The sample I gave before with the JmsStart event basically:
public class JmsRegistrar {
@Inject
@JmsConnectionFactory(...)
private ConnectionFactory factory;
@Inject
@JmsQueue(...)
private Queue queue;
public void startJms(@Observes JmsStart start) {
start.withFactory(factory) // withFactory should be optional if only 1
bean matches it
.register(MyCdiTypedListener.class) // with defaults for all
potential config
.listenOn(queue)
.register(MyCdiTypedListener2.class, new MyLiteral())
.withMaxSessions(10)
.listenOn(Queue.class, new QueueLiteral(...))
......;
}
}
The power of it appears when you have a config injection in JmsRegistrar you can
iterate over to get the list of
listener for instance.
Also JMS resources can be decorated and referenced from qualifiers instead of
instances thanks to CDI.
It doesnt prevent the app to use @JmxListener somewhere else if the listener
doesnt need any input/config to be
registered.
I'm trying to understand this. Are you suggesting that
1. When the application is started an event of type JmsStart is fired. This class
will be defined by JMS and
implemented by the application server.
2. The application defines a class (in this example called JmsRegistrar). This has a
method startJms which receives
the event.
3. JmsStart (the event class) has several builder methods. The most important of
these is register() which you can
use to specify the class of a listener. The other methods withFactory, register,
withMaxSession and listenOn specify
things like which connection factory is used, which queue is used and so on.
This doesn't look very different from the normal JMS API, except that it uses a
builder pattern and is triggered
automatically at startup. Apart from triggering the initial event, what is CDI doing
for you here?
Yes this is it, few details important for CDI:
1- ensure JMS is CDI ready - ie dont use it before the start event, if JMS uses
@Initialized(ApplicationScoped) then the
app cant use it for instance, same using extension AfterValidationDeployment etc...so
this event is just to ensure we
dont use "JMS CDI" too early
2- JMS can use contextual instances implicitely which is not the case in SE
otherwise you are right the API is just fluent compared to what is already there - found
it nicer to expose but this
point is maybe personal.
OK. I'm interested in your statement "JMS can use contextual instances
implicitly". That suggests that the method
register(MyCdiTypedListener.class) would use some CDI API such as Instance.get() to obtain
an instance of
MyCdiTypedListener rather than simply using new. Is that right?
What I can't see yet is how to pass in the configuration parameters for specifying
things like the queue. These are not
qualifiers which are used by Instance.select() to determine which class is instantiated.
They are values which are used
by the bean's postConstruct method (as extended by the portable extension) to
initialise the bean.
Nigel