Java tutorial
/* * 2001-2009, Progress Software Corporation and/or its subsidiaries or affiliates. All rights reserved. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. Sample Application Writing a Basic JMS Application using Publish and Subscribe using Message Selectors This sample publishes messages and sets a property in the message header when publishing messages. The subscriber set a message selector to select these messages. In this sample we name the property "Department" Usage: java SelectorChat -b <broker:port> -u <username> -p <password> -v <property> -s <selector> -b broker:port points to your message broker Default: tcp://localhost:61616 -u username must be unique (but is not checked) -p password (optional) password for user (not checked) Default: password -s selection required, selection value to set to message property Suggested demonstration: - In separate console windows with the environment set, start instances of the application under unique user names. For example: java SelectorChat -u BOB -s MARKETING java SelectorChat -u JANE -s MARKETING - Enter text and then press Enter to publish the message. - See messages appear under the various user names as you enter messages in each console window. - Try starting a new instance with a different message selector - Stop a session by pressing CTRL+C in its console window. */ import org.apache.activemq.*; public class SelectorChat implements javax.jms.MessageListener { private static final String APP_TOPIC = "jms.samples.chat"; private static final String PROPERTY_NAME = "Department"; private static final String DEFAULT_BROKER_NAME = "tcp://localhost:61616"; private static final String DEFAULT_PASSWORD = "password"; private javax.jms.Connection connect = null; private javax.jms.Session pubSession = null; private javax.jms.Session subSession = null; private javax.jms.MessageProducer publisher = null; /** Create JMS client for publishing and subscribing to messages. */ private void chatter(String broker, String username, String password, String selection) { // Create a connection. try { javax.jms.ConnectionFactory factory; factory = new ActiveMQConnectionFactory(username, password, broker); connect = factory.createConnection(username, password); pubSession = connect.createSession(false, javax.jms.Session.AUTO_ACKNOWLEDGE); subSession = connect.createSession(false, javax.jms.Session.AUTO_ACKNOWLEDGE); } catch (javax.jms.JMSException jmse) { System.err.println("error: Cannot connect to Broker - " + broker); jmse.printStackTrace(); System.exit(1); } // Create Publisher and Subscriber to 'chat' topics try { javax.jms.Topic topic = pubSession.createTopic(APP_TOPIC); // NOTE: The subscriber's message selector will now be set: javax.jms.MessageConsumer subscriber = subSession.createConsumer(topic, PROPERTY_NAME + " = \'" + selection + "\'", false); subscriber.setMessageListener(this); publisher = pubSession.createProducer(topic); // Now that setup is complete, start the Connection connect.start(); } catch (javax.jms.JMSException jmse) { jmse.printStackTrace(); System.exit(1); } try { // Read all standard input and send it as a message. java.io.BufferedReader stdin = new java.io.BufferedReader(new java.io.InputStreamReader(System.in)); System.out.println("\nSelectorChat application:\n" + "===========================\n" + "The application user " + username + " connects to the broker at " + DEFAULT_BROKER_NAME + ".\n" + "The application will publish messages with " + PROPERTY_NAME + " set to " + selection + " to the " + APP_TOPIC + " topic .\n" + "The application also subscribes to that topic, selecting only messages where " + PROPERTY_NAME + " is " + selection + ".\n" + "Type some text, and then press Enter to publish it as a TextMesssage from " + username + ".\n"); while (true) { String s = stdin.readLine(); if (s == null) exit(); else if (s.length() > 0) { javax.jms.TextMessage msg = pubSession.createTextMessage(); msg.setText(username + ": " + s); // NOTE: here we set a property on messages to be published: msg.setStringProperty(PROPERTY_NAME, selection); publisher.send(msg); } } } catch (java.io.IOException ioe) { ioe.printStackTrace(); } catch (javax.jms.JMSException jmse) { jmse.printStackTrace(); } } /** * Handle the message * (as specified in the javax.jms.MessageListener interface). */ public void onMessage(javax.jms.Message aMessage) { try { // Cast the message as a text message. javax.jms.TextMessage textMessage = (javax.jms.TextMessage) aMessage; // This handler reads a single String from the // message and prints it to the standard output. try { String string = textMessage.getText(); System.out.println(string); } catch (javax.jms.JMSException jmse) { jmse.printStackTrace(); } } catch (java.lang.RuntimeException rte) { rte.printStackTrace(); } } /** Cleanup resources and then exit. */ private void exit() { try { connect.close(); } catch (javax.jms.JMSException jmse) { jmse.printStackTrace(); } System.exit(0); } // // NOTE: the remainder of this sample deals with reading arguments // and does not utilize any JMS classes or code. // /** Main program entry point. */ public static void main(String argv[]) { // Is there anything to do? if (argv.length == 0) { printUsage(); System.exit(1); } // Values to be read from parameters String broker = DEFAULT_BROKER_NAME; String username = null; String password = DEFAULT_PASSWORD; String selection = null; // Check parameters for (int i = 0; i < argv.length; i++) { String arg = argv[i]; // Options if (!arg.startsWith("-")) { System.err.println("error: unexpected argument - " + arg); printUsage(); System.exit(1); } else { if (arg.equals("-b")) { if (i == argv.length - 1 || argv[i + 1].startsWith("-")) { System.err.println("error: missing broker name:port"); System.exit(1); } broker = argv[++i]; continue; } if (arg.equals("-u")) { if (i == argv.length - 1 || argv[i + 1].startsWith("-")) { System.err.println("error: missing user name"); System.exit(1); } username = argv[++i]; continue; } if (arg.equals("-p")) { if (i == argv.length - 1 || argv[i + 1].startsWith("-")) { System.err.println("error: missing password"); System.exit(1); } password = argv[++i]; continue; } if (arg.equals("-s")) { if (i == argv.length - 1 || argv[i + 1].startsWith("-")) { System.err.println("error: missing selection"); System.exit(1); } selection = argv[++i]; continue; } if (arg.equals("-h")) { printUsage(); System.exit(1); } } } // Check values read in. if (username == null) { System.err.println("error: user name must be supplied"); printUsage(); } if (selection == null) { System.err.println("error: selection must be supplied"); printUsage(); System.exit(1); } // Start the JMS client for the "chat". SelectorChat chat = new SelectorChat(); chat.chatter(broker, username, password, selection); } /** Prints the usage. */ private static void printUsage() { StringBuffer use = new StringBuffer(); use.append("usage: java SelectorChat (options) ...\n\n"); use.append("options:\n"); use.append(" -b name:port Specify name:port of broker.\n"); use.append(" Default broker: " + DEFAULT_BROKER_NAME + "\n"); use.append(" -u name Specify unique user name. (Required)\n"); use.append(" -p password Specify password for user.\n"); use.append(" Default password: " + DEFAULT_PASSWORD + "\n"); use.append(" -s selection Message selector value. (Required)\n"); use.append(" -h This help screen\n"); System.err.println(use); } }