Apologies in advance if this shows up twice, but I seem to have had problems
sending from my work account...
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Hello.
I have been playing around with the Hello.java example that came with
qpid-java-client-0.24.tar.gz.
I have installed the qpidd package (the broker) on a Ubuntu 12.04 LTS
platform along with the qpid-tools package
(from the Ubuntu Software Centre).
I am looking to try and integrate the Qpid broker with JMS-based clients. I
am brand new to all of the concepts and my
understanding is possibly being confused by the differences in terminology
between JMS and Qpid elements.
I would greatly appreciate if you can indulge a few questions arising from
my initial foray...
By modifying the code to use the pub/sub API, I have arrived at this source
(Hello2.java):
--------
package org.apache.qpid.example;
import javax.jms.*;
import javax.naming.Context;
import javax.naming.InitialContext;
import java.util.Properties;
public class Hello2
{
public Hello2()
{
}
public static void main(String[] args)
{
Hello2 hello2 = new Hello2();
hello2.runTest();
}
private void runTest()
{
try {
Properties properties = new Properties();
properties.load(this.getClass().getResourceAsStream("hello2.properties"));
Context context = new InitialContext(properties);
TopicConnectionFactory topicConnectionFactory =
(TopicConnectionFactory) context.lookup("qpidConnectionfactory");
TopicConnection topicConnection =
topicConnectionFactory.createTopicConnection();
topicConnection.start();
TopicSession topicSession =
topicConnection.createTopicSession(false, Session.AUTO_ACKNOWLEDGE);
Topic topic = (Topic) context.lookup("topicExchange");
System.out.println(topic.getTopicName());
TopicPublisher topicPublisher =
topicSession.createPublisher(topic);
TopicSubscriber topicSubscriber =
topicSession.createSubscriber(topic);
TextMessage message = topicSession.createTextMessage("Hello
world!");
topicPublisher.publish(message);
message = (TextMessage)topicSubscriber.receive();
System.out.println(message.getText());
topicConnection.close();
context.close();
}
catch (Exception exp)
{
exp.printStackTrace();
}
}
}
--------
Now, hello2.properties looks like this:
--------
java.naming.factory.initial =
org.apache.qpid.jndi.PropertiesFileInitialContextFactory
# register some connection factories
# connectionfactory.[jndiname] = [ConnectionURL]
connectionfactory.qpidConnectionfactory =
amqp://guest:guest@clientid/?brokerlist='tcp://localhost:5672'
# Register an AMQP destination in JNDI
# destination.[jniName] = [Address Format]
destination.topicExchange = news-service2
#topic.topicExchange = news-service2
--------
Before running the program, I adminstratively create the topic exchange via
qpid-config:
% qpid-config add exchange topic news-service2
Now... "AS-IS", the above code/properties combination "works" - i.e. when I
compile and run Hello2.jar, I see this output:
--------
null
Hello world!
--------
If I use the command-line "qpid-stat -e", I do indeed see msgIn and msgOut
counters incrementing for the "news-service2"
topic exchange.
What I don't understand (my first question) here is why the
"topic.getTopicName()" call is returning "null" in this instance?
When I substitute "topic.topicExchange" for "destination.topicExchange" in
the hello2.properties file, I get this output:
--------
news-service2
Hello world!
--------
Here, "topic.getTopicName()" actually returns the expected string
"news-service2".
However, in this case "qpid-stat-e" shows that the corresponding topic
exchange "news-service2" has NOT changed its
msgIn/msgOut counters, BUT the counts for amq.topic have changed instead. My
second question therefore is why have these
messages ended up in amq.topic?
A final question (more of a related query). If I use the default (original)
example code Hello.java, but in hello.properties
substitute "destination.topicExchange = amq.topic" for "queue.topicExchange
= some_queue_name", I note that even if
"some_queue_name" did not exist in the broker prior to running Hello, then
it is created. This behaviour doesn't seem to work
for "topic.topicExchange" so I was wondering why the discrepancy.
Thanks for indulging these newbie questions!
Mark.
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