A simple implementation of a request/reply message exchange
/*
* @(#)RequestReplyQueue.java 1.3 02/05/02
*
* Copyright (c) 2000-2002 Sun Microsystems, Inc. All Rights Reserved.
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*/
import javax.jms.*;
/**
* The RequestReplyQueue class illustrates a simple implementation of a
* request/reply message exchange. It uses the QueueRequestor class provided
* by JMS. Providers and clients can create more sophisticated versions of
* this facility.
* <p>
* The program contains a Request class, a Reply class, a main method, and
* a method that runs the sender and receiver threads.
*
* @author Kim Haase
* @version 1.5, 08/14/00
*/
public class RequestReplyQueue {
String queueName = null;
int exitResult = 0;
/**
* The Request class represents the request half of the message exchange.
*
* @author Kim Haase
* @version 1.5, 08/14/00
*/
public class Request extends Thread {
/**
* Runs the thread.
*/
public void run() {
QueueConnectionFactory queueConnectionFactory = null;
QueueConnection queueConnection = null;
QueueSession queueSession = null;
Queue queue = null;
QueueRequestor queueRequestor = null;
TextMessage message = null;
final String MSG_TEXT = new String("Here is a request");
TextMessage reply = null;
String replyID = null;
try {
queueConnectionFactory =
SampleUtilities.getQueueConnectionFactory();
queueConnection =
queueConnectionFactory.createQueueConnection();
queueSession = queueConnection.createQueueSession(false,
Session.AUTO_ACKNOWLEDGE);
queue = SampleUtilities.getQueue(queueName, (Session) queueSession);
} catch (Exception e) {
System.out.println("Connection problem: " + e.toString());
if (queueConnection != null) {
try {
queueConnection.close();
} catch (JMSException ee) {}
}
System.exit(1);
}
/*
* Create a QueueRequestor.
* Create a text message and set its text.
* Start delivery of incoming messages.
* Send the text message as the argument to the request method,
* which returns the reply message. The request method also
* creates a temporary queue and places it in the JMSReplyTo
* message header field.
* Extract and display the reply message.
* Read the JMSCorrelationID of the reply message and confirm that
* it matches the JMSMessageID of the message that was sent.
* Finally, close the connection.
*/
try {
queueRequestor = new QueueRequestor(queueSession, queue);
message = queueSession.createTextMessage();
message.setText(MSG_TEXT);
System.out.println("REQUEST: Sending message: "
+ message.getText());
queueConnection.start();
reply = (TextMessage) queueRequestor.request(message);
System.out.println("REQUEST: Reply received: "
+ reply.getText());
replyID = new String(reply.getJMSCorrelationID());
if (replyID.equals(message.getJMSMessageID())) {
System.out.println("REQUEST: OK: Reply matches sent message");
} else {
System.out.println("REQUEST: ERROR: Reply does not match sent message");
}
} catch (JMSException e) {
System.out.println("Exception occurred: " + e.toString());
exitResult = 1;
} catch (Exception ee) {
System.out.println("Unexpected exception: " + ee.toString());
ee.printStackTrace();
exitResult = 1;
} finally {
if (queueConnection != null) {
try {
queueConnection.close();
} catch (JMSException e) {
exitResult = 1;
}
}
}
}
}
/**
* The Reply class represents the reply half of the message exchange.
*
* @author Kim Haase
* @version 1.5, 08/14/00
*/
public class Reply extends Thread {
/**
* Runs the thread.
*/
public void run() {
ConnectionFactory connectionFactory = null;
Connection connection = null;
Session session = null;
Queue queue = null;
MessageConsumer msgConsumer = null;
TextMessage message = null;
Queue tempQueue = null;
MessageProducer replyProducer = null;
TextMessage reply = null;
final String REPLY_TEXT = new String("Here is a reply");
try {
connectionFactory =
SampleUtilities.getConnectionFactory();
connection =
connectionFactory.createConnection();
session = connection.createSession(false,
Session.AUTO_ACKNOWLEDGE);
queue = SampleUtilities.getQueue(queueName, session);
} catch (Exception e) {
System.out.println("Connection problem: " + e.toString());
if (connection != null) {
try {
connection.close();
} catch (JMSException ee) {}
}
System.exit(1);
}
/*
* Create a MessageConsumer.
* Start delivery of incoming messages.
* Call receive, which blocks until it obtains a message.
* Display the message obtained.
* Extract the temporary reply queue from the JMSReplyTo field of
* the message header.
* Use the temporary queue to create a sender for the reply message.
* Create the reply message, setting the JMSCorrelationID to the
* value of the incoming message's JMSMessageID.
* Send the reply message.
* Finally, close the connection.
*/
try {
msgConsumer = session.createConsumer(queue);
connection.start();
message = (TextMessage) msgConsumer.receive();
System.out.println("REPLY: Message received: "
+ message.getText());
tempQueue = (Queue) message.getJMSReplyTo();
replyProducer = session.createProducer(tempQueue);
reply = session.createTextMessage();
reply.setText(REPLY_TEXT);
reply.setJMSCorrelationID(message.getJMSMessageID());
System.out.println("REPLY: Sending reply: " + reply.getText());
replyProducer.send(reply);
} catch (JMSException e) {
System.out.println("Exception occurred: " + e.toString());
exitResult = 1;
} catch (Exception ee) {
System.out.println("Unexpected exception: " + ee.toString());
ee.printStackTrace();
exitResult = 1;
} finally {
if (connection != null) {
try {
connection.close();
} catch (JMSException e) {
exitResult = 1;
}
}
}
}
}
/**
* Instantiates the Request and Reply classes and starts their
* threads.
* Calls the join method to wait for the threads to die.
*/
public void run_threads() {
Request request = new Request();
Reply reply = new Reply();
request.start();
reply.start();
try {
request.join();
reply.join();
} catch (InterruptedException e) {}
}
/**
* Reads the queue name from the command line, then calls the
* run_threads method to execute the program threads.
*
* @param args the queue used by the example
*/
public static void main(String[] args) {
RequestReplyQueue rrq = new RequestReplyQueue();
if (args.length != 1) {
System.out.println("Usage: java RequestReplyQueue <queue_name>");
System.exit(1);
}
rrq.queueName = new String(args[0]);
System.out.println("Queue name is " + rrq.queueName);
rrq.run_threads();
SampleUtilities.exit(rrq.exitResult);
}
}
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