Java tutorial
/** * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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. */ import java.io.IOException; import java.util.Arrays; import java.util.ArrayList; import java.util.Iterator; import javax.jms.Connection; import javax.jms.DeliveryMode; import javax.jms.Destination; import javax.jms.ExceptionListener; import javax.jms.JMSException; import javax.jms.Message; import javax.jms.MessageConsumer; import javax.jms.MessageListener; import javax.jms.MessageProducer; import javax.jms.Session; import javax.jms.TextMessage; import javax.jms.Topic; import org.apache.activemq.ActiveMQConnection; import org.apache.activemq.ActiveMQConnectionFactory; /** * A simple tool for consuming messages * * */ public class ConsumerTool extends Thread implements MessageListener, ExceptionListener { private boolean running; private Session session; private Destination destination; private MessageProducer replyProducer; private boolean pauseBeforeShutdown = false; private boolean verbose = true; private int maxiumMessages; private static int parallelThreads = 1; private String subject = "TOOL.DEFAULT"; private boolean topic; private String user = ActiveMQConnection.DEFAULT_USER; private String password = ActiveMQConnection.DEFAULT_PASSWORD; private String url = ActiveMQConnection.DEFAULT_BROKER_URL; private boolean transacted; private boolean durable; private String clientId; private int ackMode = Session.AUTO_ACKNOWLEDGE; private String consumerName = "James"; private long sleepTime; private long receiveTimeOut; private long batch = 10; // Default batch size for CLIENT_ACKNOWLEDGEMENT or SESSION_TRANSACTED private long messagesReceived = 0; public static void main(String[] args) { ArrayList<ConsumerTool> threads = new ArrayList(); ConsumerTool consumerTool = new ConsumerTool(); String[] unknown = CommandLineSupport.setOptions(consumerTool, args); if (unknown.length > 0) { System.out.println("Unknown options: " + Arrays.toString(unknown)); System.exit(-1); } consumerTool.showParameters(); for (int threadCount = 1; threadCount <= parallelThreads; threadCount++) { consumerTool = new ConsumerTool(); CommandLineSupport.setOptions(consumerTool, args); consumerTool.start(); threads.add(consumerTool); } while (true) { Iterator<ConsumerTool> itr = threads.iterator(); int running = 0; while (itr.hasNext()) { ConsumerTool thread = itr.next(); if (thread.isAlive()) { running++; } } if (running <= 0) { System.out.println("All threads completed their work"); break; } try { Thread.sleep(1000); } catch (Exception e) { } } Iterator<ConsumerTool> itr = threads.iterator(); while (itr.hasNext()) { ConsumerTool thread = itr.next(); } } public void showParameters() { System.out.println("Connecting to URL: " + url + " (" + user + ":" + password + ")"); System.out.println("Consuming " + (topic ? "topic" : "queue") + ": " + subject); System.out.println("Using a " + (durable ? "durable" : "non-durable") + " subscription"); System.out.println("Running " + parallelThreads + " parallel threads"); } public void run() { try { running = true; ActiveMQConnectionFactory connectionFactory = new ActiveMQConnectionFactory(user, password, url); Connection connection = connectionFactory.createConnection(); if (durable && clientId != null && clientId.length() > 0 && !"null".equals(clientId)) { connection.setClientID(clientId); } connection.setExceptionListener(this); connection.start(); session = connection.createSession(transacted, ackMode); if (topic) { destination = session.createTopic(subject); } else { destination = session.createQueue(subject); } replyProducer = session.createProducer(null); replyProducer.setDeliveryMode(DeliveryMode.NON_PERSISTENT); MessageConsumer consumer = null; if (durable && topic) { consumer = session.createDurableSubscriber((Topic) destination, consumerName); } else { consumer = session.createConsumer(destination); } if (maxiumMessages > 0) { consumeMessagesAndClose(connection, session, consumer); } else { if (receiveTimeOut == 0) { consumer.setMessageListener(this); } else { consumeMessagesAndClose(connection, session, consumer, receiveTimeOut); } } } catch (Exception e) { System.out.println("[" + this.getName() + "] Caught: " + e); e.printStackTrace(); } } public void onMessage(Message message) { messagesReceived++; try { if (message instanceof TextMessage) { TextMessage txtMsg = (TextMessage) message; if (verbose) { String msg = txtMsg.getText(); int length = msg.length(); if (length > 50) { msg = msg.substring(0, 50) + "..."; } System.out.println("[" + this.getName() + "] Received: '" + msg + "' (length " + length + ")"); } } else { if (verbose) { System.out.println("[" + this.getName() + "] Received: '" + message + "'"); } } if (message.getJMSReplyTo() != null) { replyProducer.send(message.getJMSReplyTo(), session.createTextMessage("Reply: " + message.getJMSMessageID())); } if (transacted) { if ((messagesReceived % batch) == 0) { System.out.println("Commiting transaction for last " + batch + " messages; messages so far = " + messagesReceived); session.commit(); } } else if (ackMode == Session.CLIENT_ACKNOWLEDGE) { if ((messagesReceived % batch) == 0) { System.out.println( "Acknowledging last " + batch + " messages; messages so far = " + messagesReceived); message.acknowledge(); } } } catch (JMSException e) { System.out.println("[" + this.getName() + "] Caught: " + e); e.printStackTrace(); } finally { if (sleepTime > 0) { try { Thread.sleep(sleepTime); } catch (InterruptedException e) { } } } } public synchronized void onException(JMSException ex) { System.out.println("[" + this.getName() + "] JMS Exception occured. Shutting down client."); running = false; } synchronized boolean isRunning() { return running; } protected void consumeMessagesAndClose(Connection connection, Session session, MessageConsumer consumer) throws JMSException, IOException { System.out.println("[" + this.getName() + "] We are about to wait until we consume: " + maxiumMessages + " message(s) then we will shutdown"); for (int i = 0; i < maxiumMessages && isRunning();) { Message message = consumer.receive(1000); if (message != null) { i++; onMessage(message); } } System.out.println("[" + this.getName() + "] Closing connection"); consumer.close(); session.close(); connection.close(); if (pauseBeforeShutdown) { System.out.println("[" + this.getName() + "] Press return to shut down"); System.in.read(); } } protected void consumeMessagesAndClose(Connection connection, Session session, MessageConsumer consumer, long timeout) throws JMSException, IOException { System.out.println( "[" + this.getName() + "] We will consume messages while they continue to be delivered within: " + timeout + " ms, and then we will shutdown"); Message message; while ((message = consumer.receive(timeout)) != null) { onMessage(message); } System.out.println("[" + this.getName() + "] Closing connection"); consumer.close(); session.close(); connection.close(); if (pauseBeforeShutdown) { System.out.println("[" + this.getName() + "] Press return to shut down"); System.in.read(); } } public void setAckMode(String ackMode) { if ("CLIENT_ACKNOWLEDGE".equals(ackMode)) { this.ackMode = Session.CLIENT_ACKNOWLEDGE; } if ("AUTO_ACKNOWLEDGE".equals(ackMode)) { this.ackMode = Session.AUTO_ACKNOWLEDGE; } if ("DUPS_OK_ACKNOWLEDGE".equals(ackMode)) { this.ackMode = Session.DUPS_OK_ACKNOWLEDGE; } if ("SESSION_TRANSACTED".equals(ackMode)) { this.ackMode = Session.SESSION_TRANSACTED; } } public void setClientId(String clientID) { this.clientId = clientID; } public void setConsumerName(String consumerName) { this.consumerName = consumerName; } public void setDurable(boolean durable) { this.durable = durable; } public void setMaxiumMessages(int maxiumMessages) { this.maxiumMessages = maxiumMessages; } public void setPauseBeforeShutdown(boolean pauseBeforeShutdown) { this.pauseBeforeShutdown = pauseBeforeShutdown; } public void setPassword(String pwd) { this.password = pwd; } public void setReceiveTimeOut(long receiveTimeOut) { this.receiveTimeOut = receiveTimeOut; } public void setSleepTime(long sleepTime) { this.sleepTime = sleepTime; } public void setSubject(String subject) { this.subject = subject; } public void setParallelThreads(int parallelThreads) { if (parallelThreads < 1) { parallelThreads = 1; } this.parallelThreads = parallelThreads; } public void setTopic(boolean topic) { this.topic = topic; } public void setQueue(boolean queue) { this.topic = !queue; } public void setTransacted(boolean transacted) { this.transacted = transacted; } public void setUrl(String url) { this.url = url; } public void setUser(String user) { this.user = user; } public void setVerbose(boolean verbose) { this.verbose = verbose; } public void setBatch(long batch) { this.batch = batch; } }