ActiveMQ example source code file (Vendor.java)

This example ActiveMQ source code file (Vendor.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - ActiveMQ tags/keywords

cancelled, destination, jmsexception, jmsexception, mapmessage, mapmessage, messageproducer, object, order, order, quantity, string, string, util, vendor

The ActiveMQ Vendor.java source code

/*
 *  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.util.HashMap;
import java.util.Map;
import java.util.Random;

import javax.jms.Connection;
import javax.jms.Destination;
import javax.jms.JMSException;
import javax.jms.MapMessage;
import javax.jms.Message;
import javax.jms.MessageConsumer;
import javax.jms.MessageListener;
import javax.jms.MessageProducer;
import javax.jms.Session;
import javax.jms.TemporaryQueue;

import org.apache.activemq.ActiveMQConnectionFactory;

/**
 * The Vendor synchronously, and in a single transaction, receives the
 * order from VendorOrderQueue and sends messages to the two Suppliers via
 * MonitorOrderQueue and StorageOrderQueue.
 * The responses are received asynchronously; when both responses come
 * back, the order confirmation message is sent back to the Retailer.
 */
public class Vendor implements Runnable, MessageListener {
	private String url;
	private String user;
	private String password;
	private	Session asyncSession;
	private int numSuppliers = 2;
	private Object supplierLock = new Object();
	
	public Vendor(String url, String user, String password) {
		this.url = url;
		this.user = user;
		this.password = password;
	}
	
	public void run() {
		ActiveMQConnectionFactory connectionFactory = new ActiveMQConnectionFactory(user, password, url);
		Session session = null;
		Destination orderQueue;
		Destination monitorOrderQueue;
		Destination storageOrderQueue;
		TemporaryQueue vendorConfirmQueue;
		MessageConsumer orderConsumer = null;
		MessageProducer monitorProducer = null;
		MessageProducer storageProducer = null;

		try {
			Connection connection = connectionFactory.createConnection();

			session = connection.createSession(true, Session.SESSION_TRANSACTED);
			orderQueue = session.createQueue("VendorOrderQueue");
			monitorOrderQueue = session.createQueue("MonitorOrderQueue");
			storageOrderQueue = session.createQueue("StorageOrderQueue");
			
			orderConsumer = session.createConsumer(orderQueue);
			monitorProducer = session.createProducer(monitorOrderQueue);
			storageProducer = session.createProducer(storageOrderQueue);
			
			Connection asyncconnection = connectionFactory.createConnection();
			asyncSession = asyncconnection.createSession(true, Session.SESSION_TRANSACTED);
			
			vendorConfirmQueue = asyncSession.createTemporaryQueue();
			MessageConsumer confirmConsumer = asyncSession.createConsumer(vendorConfirmQueue);
			confirmConsumer.setMessageListener(this);
			
			asyncconnection.start();

			connection.start();

		
			while (true) {
				Order order = null;
				try {
					Message inMessage = orderConsumer.receive();
					MapMessage message;
					if (inMessage instanceof MapMessage) {
						message = (MapMessage) inMessage;
						
					} else {
						// end of stream
						Message outMessage = session.createMessage();
						outMessage.setJMSReplyTo(vendorConfirmQueue);
						monitorProducer.send(outMessage);
						storageProducer.send(outMessage);
						session.commit();
						break;
					}
					
					// Randomly throw an exception in here to simulate a Database error
					// and trigger a rollback of the transaction
					if (new Random().nextInt(3) == 0) {
						throw new JMSException("Simulated Database Error.");
					}
					
					order = new Order(message);
					
					MapMessage orderMessage = session.createMapMessage();
					orderMessage.setJMSReplyTo(vendorConfirmQueue);
					orderMessage.setInt("VendorOrderNumber", order.getOrderNumber());
					int quantity = message.getInt("Quantity");
					System.out.println("Vendor: Retailer ordered " + quantity + " " + message.getString("Item"));
					
					orderMessage.setInt("Quantity", quantity);
					orderMessage.setString("Item", "Monitor");
					monitorProducer.send(orderMessage);
					System.out.println("Vendor: ordered " + quantity + " Monitor(s)");
					
					orderMessage.setString("Item", "HardDrive");
					storageProducer.send(orderMessage);
					System.out.println("Vendor: ordered " + quantity + " Hard Drive(s)");
					
					session.commit();
					System.out.println("Vendor: Comitted Transaction 1");
					
				} catch (JMSException e) {
					System.out.println("Vendor: JMSException Occured: " + e.getMessage());
					e.printStackTrace();
					session.rollback();
					System.out.println("Vendor: Rolled Back Transaction.");
				}
			}
			
			synchronized (supplierLock) {
				while (numSuppliers > 0) {
					try {
						supplierLock.wait();
					} catch (InterruptedException e) {
						e.printStackTrace();
					}
				}
			}
			
			connection.close();
			asyncconnection.close();
		
		} catch (JMSException e) {
			e.printStackTrace();
		}

	}

	public void onMessage(Message message) {
		if (!(message instanceof MapMessage)) {
			synchronized(supplierLock) {
				numSuppliers--;
				supplierLock.notifyAll();
			}
			try {
				asyncSession.commit();
				return;
			} catch (JMSException e) {
				e.printStackTrace();
			}
		}
		
		int orderNumber = -1;
		try {
			MapMessage componentMessage = (MapMessage) message;
			
			orderNumber = componentMessage.getInt("VendorOrderNumber");
			Order order = Order.getOrder(orderNumber);
			order.processSubOrder(componentMessage);
			asyncSession.commit();
			
			if (! "Pending".equals(order.getStatus())) {
				System.out.println("Vendor: Completed processing for order " + orderNumber);
				
				MessageProducer replyProducer = asyncSession.createProducer(order.getMessage().getJMSReplyTo());
				MapMessage replyMessage = asyncSession.createMapMessage();
				if ("Fulfilled".equals(order.getStatus())) {
					replyMessage.setBoolean("OrderAccepted", true);
					System.out.println("Vendor: sent " + order.quantity + " computer(s)");
				} else {
					replyMessage.setBoolean("OrderAccepted", false);
					System.out.println("Vendor: unable to send " + order.quantity + " computer(s)");
				}
				replyProducer.send(replyMessage);
				asyncSession.commit();
				System.out.println("Vender: committed transaction 2");
			}
		} catch (JMSException e) {
			e.printStackTrace();
		}
	}

	public static class Order {
		private static Map<Integer, Order> pendingOrders = new HashMap();
		private static int nextOrderNumber = 1;

		private int orderNumber;
		private int quantity;
		private MapMessage monitor = null;
		private MapMessage storage = null;
		private MapMessage message;
		private String status;
		
		public Order(MapMessage message) {
			this.orderNumber = nextOrderNumber++;
			this.message = message;
			try {
				this.quantity = message.getInt("Quantity");
			} catch (JMSException e) {
				e.printStackTrace();
				this.quantity = 0;
			}
			status = "Pending";
			pendingOrders.put(orderNumber, this);
		}
		
		public Object getStatus() {
			return status;
		}
		
		public int getOrderNumber() {
			return orderNumber;
		}
		
		public static int getOutstandingOrders() {
			return pendingOrders.size();
		}
		
		public static Order getOrder(int number) {
			return pendingOrders.get(number);
		}
		
		public MapMessage getMessage() {
			return message;
		}
		
		public void processSubOrder(MapMessage message) {
			String itemName = null;
			try {
				itemName = message.getString("Item");
			} catch (JMSException e) {
				e.printStackTrace();
			}
			
			if ("Monitor".equals(itemName)) {
				monitor = message;
			} else if ("HardDrive".equals(itemName)) {
				storage = message;
			}
			
			if (null != monitor && null != storage) {
				// Received both messages
				try {
					if (quantity > monitor.getInt("Quantity")) {
						status = "Cancelled";
					} else if (quantity > storage.getInt("Quantity")) {
						status = "Cancelled";
					} else {
						status = "Fulfilled";
					}
				} catch (JMSException e) {
					e.printStackTrace();
					status = "Cancelled";
				}
			}
		}		
	}

	public static void main(String[] args) {
		String url = "tcp://localhost:61616";
		String user = null;
		String password = null;
		
		if (args.length >= 1) {
			url = args[0];
		}
		
		if (args.length >= 2) {
			user = args[1];
		}

		if (args.length >= 3) {
			password = args[2];
		}
		
		Vendor v = new Vendor(url, user, password);
		
		new Thread(v, "Vendor").start();
	}	
}