mq5.0-source.src.share.java.examples.jms20.asynctopicconsumer.AsyncTopicConsumer Maven / Gradle / Ivy
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import javax.jms.*;
import java.util.concurrent.CountDownLatch;
/**
* The AsyncTopicConsumer.class receives messages from
* a topic using asynchronous message delivery.
*
* Run this program in conjunction with SendMsgsToTopic.
* Specify a topic name on the command line when you run
* the program. By default, the program receives one message. Specify a number
* after the topic name to receive that number of messages.
*/
public class AsyncTopicConsumer {
private String destName = null;
private int noOfMsgs;
static int exitcode = 0;
/**
* Main method.
*
* @param args the topic used by the example and, optionally, the
* number of messages to receive
*/
public static void main(String args[]) {
if ( (args.length < 1) || (args.length > 2) ) {
System.out.println("Usage: java AsyncTopicConsumer []");
System.exit(1);
}
AsyncTopicConsumer recvMsg = new AsyncTopicConsumer();
recvMsg.parseArgs(args);
try {
// Receive messages from topic
recvMsg.receivemsgs();
}catch(JMSException ex) {
ex.printStackTrace();
exitcode = 1;
}
System.exit(exitcode);
}
/**
* parseArgs method.
*
* @param args the arguments that are passed through main method
*/
public void parseArgs(String[] args){
destName = new String(args[0]);
System.out.println("Topic name is " + destName);
if (args.length == 2){
noOfMsgs = (new Integer(args[1])).intValue();
} else {
noOfMsgs = 1;
}
}
/**
* Receive messages asynchronously from the topic destination
*
* @param none
* @throws JMSException
*/
public void receivemsgs() throws JMSException {
// Create connection factory for the MQ client
ConnectionFactory cf = new com.sun.messaging.ConnectionFactory();
// JMSContext will be closed automatically with the try-with-resources block
try (JMSContext jmsContext = cf.createContext(JMSContext.AUTO_ACKNOWLEDGE);) {
System.out.println("Created jms context successfully");
// Create topic
Topic topic = jmsContext.createTopic(destName);
System.out.println("Created topic successfully");
// Create consumer
JMSConsumer consumer = jmsContext.createConsumer(topic);
MessageHandler listener = new MessageHandler(noOfMsgs);
// Set message listener on consumer
consumer.setMessageListener(listener);
jmsContext.start();
listener.await();
}
}
/**
* The MessageHandler class implements the MessageListener interface by
* defining an onMessage method for the AsyncTopicConsumer class.
*/
static class MessageHandler implements javax.jms.MessageListener {
private CountDownLatch countDownLatch;
private int msgsRecv;
private int totalMsgs;
MessageHandler(int noOfMsgs) {
totalMsgs = noOfMsgs;
countDownLatch = new CountDownLatch(1);
}
/**
* Casts the message to a TextMessage and displays its text.
* The message listener sets its CounDownLatch to all
* done processing messages.
*
* @param message the incoming message
*/
public void onMessage(Message message) {
//Receive messages
TextMessage msg = (TextMessage) message;
try {
if(msg != null) {
msgsRecv ++;
// Get message body as String
String body = msg.getBody(String.class);
System.out.println("Message Received : "+body);
}
if ( msgsRecv == totalMsgs) {
countDownLatch.countDown();
}
} catch( JMSException ex) {
System.out.println("Exception in onMessage(): " + ex.toString());
countDownLatch.countDown();
}
}
public void await() {
try {
countDownLatch.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}