2014-10-31 06:20:28 -04:00
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2014-11-19 03:44:57 -05:00
< title > ActiveMQ JMS Topic Selector Example 1< / title >
2014-10-31 06:20:28 -04:00
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< h1 > JMS Topic Selector Example 1< / h1 >
< p > This example shows how messages can be consumed from a topic using Message Selectors.< / p >
< p > Consumers (or Subscribers) will only consume messages routed to a topic that match the provided selector< / p >
< p > Topics and selectors are a standard part of JMS, please consult the JMS 1.1 specification for full details.< / p >
< h2 > Example step-by-step< / h2 >
< p > < i > To run the example, simply type < code > mvn verify< / code > from this directory< / i > < / p >
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< li > First we need to get an initial context so we can look-up the JMS connection factory and destination objects from JNDI. This initial context will get it's properties from the < code > client-jndi.properties< / code > file in the directory < code > ../common/config< / code > < / li >
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< code > initialContext = getContext();< / code >
< / pre >
< li > We look-up the JMS topic object from JNDI< / li >
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< code > Topic topic = (Topic) initialContext.lookup("/topic/exampleTopic");< / code >
< / pre >
< li > We look-up the JMS connection factory object from JNDI< / li >
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< code > ConnectionFactory cf = (ConnectionFactory) initialContext.lookup("/ConnectionFactory");< / code >
< / pre >
< li > We create a JMS connection< / li >
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< code > connection = cf.createConnection();< / code >
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< li > We create a JMS session. The session is created as non transacted and will auto acknowledge messages.< / li >
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< code > Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);< / code >
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< li > We create a JMS message producer on the session. This will be used to send the messages.< / li >
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< code > MessageProducer messageProducer = session.createProducer(topic);< / code >
< / pre >
< li > Create one non-durable subscriber with a specific filter< / li >
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< code > MessageConsumer messageConsumer1 = session.createConsumer(topic, "someID=1", false);< / code >
< / pre >
< li > Create a second non-durable subscriber with a specific filter< / li >
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< code > MessageConsumer messageConsumer2 = session.createConsumer(topic, "someID=2", false);< / code >
< / pre >
< li > Create a third non-durable subscriber without any filters, and it should receive the complete set of messages< / li >
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< code > MessageConsumer messageConsumer3 = session.createConsumer(topic, "someID=2", false);< / code >
< / pre >
< li > Send 20 messages, 10 with someID=1, 10 with someID=2 < / li >
< pre class = "prettyprint" > < code >
for (int i = 1; i < 10 ; i + + )
{
for (int someID = 1; someID < = 2; someID++)
{
TextMessage message1 = session.createTextMessage("This is a text message " + i +
" sent for someID=" +
someID);
message1.setIntProperty("someID", someID);
producer.send(message1);
System.out.println("Sent message: " + message1.getText());
}
}< / code > < / pre >
< li > We start the connection. In order for delivery to occur on any consumers or subscribers on a connection, the connection must be started< / li >
< pre class = "prettyprint" > < code > connection.start();< / code >
< / pre >
< li > Consume the messages from MessageConsumer1, filtering out someID=2< / li >
< pre class = "prettyprint" > < code >
for (;;)
{
TextMessage messageReceivedA = (TextMessage)messageConsumer1.receive(1000);
if (messageReceivedA == null)
{
break;
}
System.out.println("messageConsumer1 received " + messageReceivedA.getText() +
" someID = " +
messageReceivedA.getIntProperty("someID"));
}< / code > < / pre >
< li > Consume the messages from MessageConsumer2, filtering out someID=1< / li >
< pre class = "prettyprint" > < code >
for (;;)
{
TextMessage messageReceivedB = (TextMessage)messageConsumer2.receive(1000);
if (messageReceivedB == null)
{
break;
}
System.out.println("messageConsumer2 received " + messageReceivedB.getText() +
" someID = " +
messageReceivedB.getIntProperty("someID"));
}< / code > < / pre >
< li > Consume the messages from MessageConsumer3, receiving the complete set of messages< / li >
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for (;;)
{
TextMessage messageReceivedC = (TextMessage)messageConsumer3.receive(1000);
if (messageReceivedC == null)
{
break;
}
System.out.println("messageConsumer3 received " + messageReceivedC.getText() +
" someID = " +
messageReceivedC.getIntProperty("someID"));
}< / code > < / pre >
< li > Close the consumers< / li >
< pre class = "prettyprint" > < code > subscriberA.close();< / code > < / pre >
< pre class = "prettyprint" > < code > subscriberB.close();< / code > < / pre >
< li > Delete the subscriptions when you're done< / li >
< pre class = "prettyprint" > < code > session.unsubscribe("sub-a1");< / code > < / pre >
< pre class = "prettyprint" > < code > session.unsubscribe("sub-a2");< / code > < / pre >
< li > And finally, < b > always< / b > remember to close your JMS connections and resources after use, in a < code > finally< / code > block. Closing a JMS connection will automatically close all of its sessions, consumers, producer and browser objects< / li >
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< code > finally
{
if (initialContext != null)
{
initialContext.close();
}
if (connection != null)
{
connection.close();
}
}< / code >
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