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 This sample publishes and subscribes to a specified topic. Text you enter is published and then received by all subscribers. Usage: java Chat -b <broker:port> -u <username> -p <password> -b broker:port points to your message broker Default: tcp://localhost:61616 -u username must be unique (but is not checked) -p password password for user (not checked) Suggested demonstration: - In separate console windows with the environment set, start instances of the application under unique user names. For example: java Chat -b tcp://localhost:61616 -u SALES java Chat -b tcp://localhost:61616 -u 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. - Stop a session by pressing CTRL+C in its console window. */ import org.apache.activemq.*; public class Chat implements javax.jms.MessageListener { private static final String APP_TOPIC = "jms.samples.chat"; private static final String DEFAULT_USER = "Chatter"; 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) { // 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); javax.jms.MessageConsumer subscriber = subSession.createConsumer(topic); subscriber.setMessageListener(this); publisher = pubSession.createProducer(topic); // Now that setup is complete, start the Connection connect.start(); } catch (javax.jms.JMSException jmse) { jmse.printStackTrace(); } 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("\nChat application:\n" + "=================\n" + "The application user " + username + " connects to the broker at " + DEFAULT_BROKER_NAME + ".\n" + "The application will publish messages to the " + APP_TOPIC + " topic.\n" + "The application also subscribes to that topic to consume any messages published there.\n\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); 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; // Check parameters for (int i = 0; i < argv.length; i++) { String arg = argv[i]; 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("-h")) { printUsage(); System.exit(1); } // Invalid argument System.err.println("error: unexpected argument: " + arg); printUsage(); System.exit(1); } // Check values read in. if (username == null) { System.err.println("error: user name must be supplied"); printUsage(); System.exit(1); } // Start the JMS client for the "chat". Chat chat = new Chat(); chat.chatter(broker, username, password); } /** Prints the usage. */ private static void printUsage() { StringBuffer use = new StringBuffer(); use.append("usage: java Chat (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(" -h This help screen.\n"); System.err.println(use); } }