Thanks again to Rob and Robbie for their answers thus far!
So I managed to slap (i.e. Frankenstein) together two pieces of
example/client code in order to attempt to facilitate a bridge of sorts
between two disparate queues.
For this test, I'm using an ActiveMQ broker with two client processes/JVMs
(client1 and client2).
The ActiveMQ broker is configured with 2 active protocols (transport
connectors) - Openwire (standard) on port 61616, and AMQP (1.0) on port 5673
(only because I was experimenting previously with the Qpid broker on the
more conventional port 5672) on the same box.
client1 is a process based purely on an ActiveMQ Java/JMS openwire client
(Publisher.java) example and its only purpose is to publish a TextMessage
into Q1 via the openwire (tcp://) connection URL.
client2 contains client code (and is linked/run with .jar libraries) for
both ActiveMQ AND Qpid JMS (AMQP 1.0). Its intent is to read messages from
Q1 (via ActiveMQ) and re-deliver them into Q2 (via AMQP). This situation is
a little contrived to start with, as eventually Q2 may well be on a
physically separate broker on a physically separate machine.
So far, so good. I did some basic testing and proved my single client2
process can successfully (independently) interact with both queues (via both
protocols).
My issue is now this:
If I receive a "TextMessage" in client2 using "consumer2" (a MessageConsumer
for the ActiveMQ connection/session), this message object/entity ("msg") is
not just something I can use (unaltered) to "send" via client2's "producer2"
(a MessageProducer for the AMQP connection/session). Indeed, if I just try
and "producer2.send(msg)", I get a Java exception at runtime. Something
like:
"javax.jms.JMSException: Unresolvable destination:
org.apache.qpid.amqp_1_0.jms.impl.QueueImpl.isQueue():
org.apache.qpid.amqp_1_0.jms.impl.QueueImpl@e127d8ab" on the "send" call.
I can only assume that this is because TextMessage has 2 separate
implementations context-dependant on the protocol/client interface with
which we are dealing.
Some digging (printing out the .getClass() results) shows that the msg
received is something like an
org.apache.activemq.command.ActiveMQTextMessage, and the message needed to
be sent is actually an org.apache.qpid.amqp_1_0.jms.impl.TestMessageImpl.
If this is the case, what is the best way to solve this problem.
If msg has a number of header and application-defined property attributes
(never minding the body), how exactly is client2 supposed to copy/preserve
them all across into a TextMessage object implementation suitable for
delivery to Q2. Will client2 need to know the exact structure of the
messages in order to deconstruct and reconstruct to satisfy the protocol
bridging??
As ever, any help with this would be hugely appreciated...
Thanks in advance,
Mark.
-----Original Message-----
From: Rob Godfrey
Sent: Monday, February 17, 2014 5:54 PM
To: users@qpid.apache.org
Subject: Re: New User JMS API Questions
On 18 February 2014 01:11, Mark Barker wrote:
Robbie,
thanks again for your answers.
As for your first suggestion:
"connecting an ActiveMQ JMS client to the ActiveMQ
broker and a Qpid JMS client to the Qpid broker within the same JVM"
Is this going to be possible in practice? I'm something of a novice at
Java too. Will there be some kind of conflict if trying to use both the
ActiveMQ JMS client and the Qpid JMS client APIs in the same process? How
would/could this be done (example build command)? Thus far I have been
building simple example code from the command line and referencing the
relevant .jar dependency in the classpath params for both javac (build)
and
java (runtime).
There shouldn't be an issue as long as there are no conflicts between the
dependencies of the ActiveMQ client and the Qpid client. The Qpid clients
aim to have as few dependencies as possible, so there really shouldn't be
an issue.
Finally,
today I've been looking at getting the simple Hello.java example running
on the ActiveMQ broker.
Obviously, this means I have to use a JMS AMQP 1.0 client, so I've been
using the Qpid JMS 1.0 client.
I've encountered some issues which seem to relate to the Connection URL
syntax from the JNDI (hello.properties) file.
For instance,
in a previous Qpid client talking AMQP 0-10 with a Qpid broker, I used:
amqp://username:password@clientid/test?brokerlist='tcp://localhost:5672'
however I've read and seen in practice that this won't work with the 1.0
client.
Instead I have to use something like:
amqp://username:password@localhost:5672
Can somebody please point me to the relevant documentation that explains
this difference in syntax. For all my digging on the Qpid website, I can
only find examples of the first/former (0-10 style), with no disclaimers
or
caveats regarding the 1.0 client.
No - there isn't a lot (or indeed really any) documentation around the AMQP
1.0 client. As you've noted the syntax is a little different from the 0-10
style... but you've pretty much got all of the syntax already.
There are currently a number of options (set in the normal URI way:
amqp://username:password@host:port?option1=value1&option2=value2...) to
fine tune some AMQP settings. If you are interested you can look in the
code which parses them here:
https://svn.apache.org/viewvc/qpid/trunk/qpid/java/amqp-1-0-client-jms/src/main/java/org/apache/qpid/amqp_1_0/jms/impl/ConnectionFactoryImpl.java?revision=1557982&view=markup&pathrev=1568703
Between lines 295 and 381 you will see the available options defined along
with a brief description of their purpose.
In addition, I've found I can use "queue://" or "topic://" prefixes in the
JNDI properties to specify the object type when using the generic
interface
(i.e. general instead of p2p/pub-sub). Is that syntax a feature of the
AMQP
protocol, or something specific to the Qpid client or ActiveMQ broker? I
can't find much mention of it anywhere.
That's something specific to the ActiveMQ broker.
Thanks again for giving these questions your attention!!
-- Rob
-----Original Message----- From: Robbie Gemmell
Sent: Saturday, February 15, 2014 2:57 PM
To: users@qpid.apache.org
Subject: Re: New User JMS API Questions
On 14 February 2014 04:55, Mark Barker wrote:
If anyone has a tried this, or can confirm:
will it be possible to have a JMS client using an ActiveMQ broker on one
machine (or maybe a producer/consumer pair), ultimately sending a message
which then routes to a Qpid broker and associated local JMS consumer on a
second machine (preserving all standard and application-specific JMS
message headers/properties). Has this been done and are there further
tricks, considerations and caveats here?
Maybe the ActiveMQ JMS consumer process on the first machine makes the
routing decision and then places the message via a producer instance for
the Qpid broker on the 2nd machine?
It sounds like you are talking about bridging two brokers, which you
presumably do either by connecting an ActiveMQ JMS client to the ActiveMQ
broker and a Qpid JMS client to the Qpid broker within the same JVM, or by
using the Qpid AMQP 1.0 JMS client to connect to both brokers.
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