JMS Quick Start Using Apache ActiveMQ

Read first JMS First Impression in the previous post. A JMS message has three parts:
1. Header, consists of: JMSDestination, JMSDeliveryMode, JMSExpiration, JMSPriority, JMSMessageID, JMSTimestamp, JMSCorrelationID, JMSReplyTo, JMSType, JMSRedelivered.
2. Properties (optional). If we need addition values besides header fields, we can set and create message properties.
3. Body (optional). JMS API defined five message body formats, also called message types, consists of: TextMessage, MapMessage, BytesMessage, StreamMessage, ObjectMessage, Message.

JMS Message delivery styles. JMS supports synchronous and asynchronous delivery messages:
1. Synchronous Delivery. For example:
A client can request the next message from a message consumer using one of its receive methods. There are several variations of receive that allow a client to poll or wait for the next message.

QueueReceiver receiver = null;
receiver = session.createReceiver(queue);
StreamMessage stockMessage;
stockMessage = (StreamMessage)receiver.receive();

In the above code fragment, the receiver will wait indefinitely for a message. Alternatively, we could have specified a timeout in milliseconds, such as:

// wait for 10 seconds only.
stockMessage = (StreamMessage)receiver.receive(10*1000);

Or, no wait at all:

// Don’t wait?
stockMessage = (StreamMessage)receiver.receiveNoWait();

2. Asynchronous Delivery
Instead of waiting/polling the message consumer for messages, a client can register a message listener with a message consumer. A message listener is an object that implements the MessageListener.

// asynchronous reader, register a message listener.
// listener will be called for each message that come into the queue 
receiver.setMessageListener(listener);

At last, but not at least. We will make a Point-to-Point Simple Calculator Application. Client will write message in queue in XML format after got request from user and read synchronously a response queue from server with specific time out by using a selector. Server will read request queue asynchronously and write response in response queue. I'm using Netbeans 6.5, and Spring Framework. Also prepare the other library like jms.jar, dom4j.jar, and Apache ActiveMQ library. Create a new Java application named CalculatorMQ. Create new package named com.ndung.mq.util. In this package we will write all utility class that needed by JMS and MQ Vendor. The First class named MQConfig.java.

package com.ndung.mq.util;

public class MQConfig {
    private String queueName;
    private int timeout;

    //getter & setter
}

The second class named MQWriter.java. This class will be used to write message in queue.

package com.ndung.mq.util;

import java.io.*;
import java.util.Map;
import java.util.Properties;
import javax.jms.*;
import javax.naming.*;

public class MQWriter {

    private ConnectionFactory queueConnectionFactory;
    private QueueConnection queueConnection;
    private QueueSession queueSession;
    private Queue queue;
    private QueueSender queueSender;
    private MQConfig config;

    public MQWriter(MQConfig config) {
        this.config = config;
    }

    public void init() {
        openConnection();
    }

    public void terminate() {
        try {
            if (queueConnection != null) {
                queueConnection.close();
                queueConnection = null;
            }
        } catch (JMSException e) {
            e.printStackTrace();
        }
    }

    public void openConnection(){
        try {
            Properties props = new Properties();
            props.load(new FileInputStream(new File("src/jndi.properties")));
            Context jndiContext = new InitialContext(props);
            queueConnectionFactory = (ConnectionFactory) jndiContext.lookup("ConnectionFactory");
            queueConnection = (QueueConnection) queueConnectionFactory.createConnection();
            queueConnection.start();
        } catch (NamingException ne) {
            ne.printStackTrace();
        } catch (JMSException je) {
            je.printStackTrace();        
        } catch (IOException ie) {
            ie.printStackTrace();
        }
    }

    public void write(String message, Map properties) throws JMSException {
        queueSender = null;
        queueSession = null;
        try {
            queueSession = queueConnection.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);
            queue = queueSession.createQueue(config.getQueueName());
            queueSender = queueSession.createSender(queue);
            TextMessage textMessage = queueSession.createTextMessage();
            if (properties != null || properties.size() != 0) {
                for (Object o : properties.keySet()) {
                    if (o instanceof String)
                        textMessage.setStringProperty(o.toString(), properties.get(o).toString());
                    if (o instanceof Integer)
                        textMessage.setIntProperty(o.toString(), Integer.parseInt(properties.get(o).toString()));
                    if (o instanceof Long)
                        textMessage.setLongProperty(o.toString(), Long.parseLong(properties.get(o).toString()));
                }
            }
            textMessage.setText(message);
            queueSender.send(textMessage);
        } catch (JMSException e) {
            e.printStackTrace();
        } finally {
            if (queueSender != null)
                queueSender.close();
            if (queueSession != null)
                queueSession.close();
        }
    }
}

The third class named MQSyncReader.java. This class will read message in queue synchronously.

package com.ndung.mq.util;

import java.io.*;
import java.util.Properties;
import javax.jms.*;
import javax.naming.*;

public class MQSyncReader {

    private ConnectionFactory queueConnectionFactory;
    private QueueConnection queueConnection;
    private QueueSession queueSession;
    private Queue queue;
    private QueueReceiver queueReceiver;
    private MQConfig config;

    public MQSyncReader(MQConfig config) {
        this.config = config;
    }

    public void init() {
        openConnection();
    }

    public void terminate() {
        try {
            if (queueSession != null)
                queueSession.close();
            if (queueConnection != null)
                queueConnection.close();
        } catch (JMSException e) {
            e.printStackTrace();
        }
    }

    public void openConnection() {
        try {
            Properties props = new Properties();
            props.load(new FileInputStream(new File("src/jndi.properties")));
            Context jndiContext = new InitialContext(props);

            queueConnectionFactory = (ConnectionFactory) jndiContext.lookup("ConnectionFactory");
            queueConnection = (QueueConnection) queueConnectionFactory.createConnection();
            queueSession = queueConnection.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);
            queueConnection.start();
        } catch (NamingException ne) {
            ne.printStackTrace();
        } catch (JMSException je) {
            je.printStackTrace();
        } catch (IOException ie) {
            ie.printStackTrace();
        }
    }

    public String read(String selector) throws JMSException {
        queueReceiver = null;
        String out = "";
        try {
            queue = queueSession.createQueue(config.getQueueName());
            if (selector != null || !selector.equals("")) {
                queueReceiver = queueSession.createReceiver(queue, selector);
            } else {
                queueReceiver = queueSession.createReceiver(queue);
            }
            TextMessage textMessage = null;
            if (config.getTimeout() != -1)
                textMessage = (TextMessage) queueReceiver.receive(config.getTimeout());
            else
                textMessage = (TextMessage) queueReceiver.receive();
            if (textMessage != null)
                out = textMessage.getText();
        } catch (JMSException je) {
            je.printStackTrace();
        } finally {
            if (queueReceiver != null)
                queueReceiver.close();
        }
        return out;
    }
}

The third class named MQAsyncReader.java. This class will read message in queue asynchronously.

package com.ndung.mq.util;

import java.io.*;
import java.util.Properties;
import javax.jms.*;
import javax.naming.*;

public class MQAsyncReader implements Runnable{
    
    private ConnectionFactory queueConnectionFactory;
    private QueueConnection queueConnection;
    private QueueSession queueSession;
    private Queue queue;
    private QueueReceiver queueReceiver;
    private MQConfig config;  
    private MessageListener listener;
    private volatile Thread thread = null;

    public MQAsyncReader(MQConfig config, MessageListener listener) {
        this.config = config;
        this.listener = listener;
    }

    public void start(){
        try{
            Properties props = new Properties();
            props.load(new FileInputStream(new File("src/jndi.properties")));
            Context jndiContext = new InitialContext(props);

            queueConnectionFactory = (ConnectionFactory) jndiContext.lookup("ConnectionFactory");
            queueConnection = (QueueConnection) queueConnectionFactory.createConnection();
            queueSession = queueConnection.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);
            queueConnection.start();
            queue = queueSession.createQueue(config.getQueueName());
            queueReceiver = queueSession.createReceiver(queue);
            thread = new Thread(this);
            thread.start();
        }
        catch(NamingException ne){
            ne.printStackTrace();
        }
        catch(JMSException je){
            je.printStackTrace();
        } catch (IOException ie) {
            ie.printStackTrace();
        }
    }

    public void stop() throws JMSException {
        thread.interrupt();
        thread = null;
        if (queueReceiver != null)
            queueReceiver.close();        
        if (queueSession != null) 
            queueSession.close();        
        if (queueConnection != null)
            queueConnection.close();        
    }

    public void run() {
        Thread thisThread = Thread.currentThread();
        while (thisThread == thread) {
            try {
                Thread.sleep(500);
            } catch (InterruptedException ie) {
                ie.printStackTrace();
                break;
            }

            try{
                queueReceiver.setMessageListener(listener);
            }
            catch(JMSException ex){
                ex.printStackTrace();
            }
        }
    }
}

Then we will make client application. Create package named com.ndung.calc.client. Create two classes named Client.java and Main.java.

package com.ndung.calc.client;

import com.ndung.mq.util.MQSyncReader;
import com.ndung.mq.util.MQWriter;
import java.util.HashMap;
import java.util.Map;
import javax.jms.JMSException;

public class Client {
    private MQWriter mQWriter;
    private MQSyncReader mQSyncReader;
    private String transid;

    public Client(MQWriter mQWriter, MQSyncReader mQSyncReader){
        this.mQWriter = mQWriter;
        this.mQSyncReader = mQSyncReader;
    }

    public String execute(int arg1, String operator, int arg2) throws JMSException{
        this.transid = String.valueOf(System.currentTimeMillis());
        String message = "\n" +
                "\n" +
                ""+arg1+"\n"+
                ""+operator+"\n"+
                ""+arg2+"\n"+
                "";
        queuePullRequest(message);
        String result = lookupFromQueue();        
        return result;
    }

    private void queuePullRequest(String message) throws JMSException {
        Map map = new HashMap();
        map.put("TransactionID", transid);        
        mQWriter.write(message, map);
    }

    private String lookupFromQueue() throws JMSException{
        StringBuffer selector = new StringBuffer(1024);
        selector.append("TransactionID = '").append(transid).append("'");
        return mQSyncReader.read(selector.toString());
    }
}

package com.ndung.calc.client;

import java.util.Scanner;
import javax.jms.JMSException;
import javax.naming.NamingException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext;

public class Main {
    public static void main(String[] args) throws NamingException, JMSException {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Please input the first arg: ");
        int arg1 = scanner.nextInt();
        System.out.print("Please input the operation, example: +,-,/,* : ");
        String operator = scanner.next();
        System.out.print("Please input the second arg: ");
        int arg2 = scanner.nextInt();

        ApplicationContext ctx = new FileSystemXmlApplicationContext("src/applicationContext.xml");
        Client client = (Client) ctx.getBean("client");
        System.out.println("The Result is = "+client.execute(arg1, operator, arg2));
    }
}

After that we make server application. Create package named com.ndung.calc.server. First make a listener class that will be registered to catch for each message that listed in request queue. This class named MQHandler.java. Then make an interface named Processor.java, that used to process request. And then four classes that implements Processor. These classes represent each calculator operation that will be handled. Last, make a Main class for server application named Main.java.

package com.ndung.calc.server;

import com.ndung.mq.util.MQWriter;
import java.io.*;
import java.util.*;
import javax.jms.*;
import org.dom4j.*;
import org.dom4j.io.SAXReader;

public class MQHandler implements MessageListener{

    Map<String, Processor> map;
    MQWriter mQWriter;

    public MQHandler(Map<String, Processor> map, MQWriter mqWriter){
        this.map = map;
        this.mQWriter =  mqWriter;
    }

    public void onMessage(Message msg) {
        try {
            if (msg instanceof TextMessage) {
                TextMessage txtMsg = (TextMessage) msg;
                String rqMsg = txtMsg.getText();
                System.out.println(rqMsg);
                String transID = txtMsg.getStringProperty("TransactionID");
                Map properties = new HashMap();
                properties.put("TransactionID", transID);
                //process response message
                InputStream in = new ByteArrayInputStream(rqMsg.getBytes());
                SAXReader reader = new SAXReader();
                Document document = reader.read(in);
                Element root = document.getRootElement();
                int arg1 = Integer.parseInt(root.elementText("arg1"));
                int arg2 = Integer.parseInt(root.elementText("arg2"));
                String operator = root.elementText("operator");
                Processor processor = map.get(operator);
                int result = 0;
                if (processor!=null)
                    result = processor.process(arg1, arg2);
                System.out.println("RESULT="+result);
                mQWriter.write(String.valueOf(result), properties);
            }
        } catch (JMSException e) {
            e.printStackTrace();
        } catch (DocumentException de){
            de.printStackTrace();
        }
    }
}

package com.ndung.calc.server;

public interface Processor {
    public int process(int arg0, int arg1);
}

package com.ndung.calc.server;

public class ProcessorAdd implements Processor{
    
    public ProcessorAdd(){        
    }

    public int process(int arg0, int arg1) {
        int result = arg0 + arg1;
        return result;
    }
}

package com.ndung.calc.server;

import com.ndung.mq.util.MQAsyncReader;
import javax.jms.JMSException;
import javax.naming.NamingException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext;

public class Main {
    private boolean active = true;
    MQAsyncReader[] reader;
    private int maxHandler = 1;
    static ApplicationContext ctx = new FileSystemXmlApplicationContext("src/applicationContext.xml");

    public void start() throws JMSException {        
        MQAsyncReader r = (MQAsyncReader) ctx.getBean("mqAsyncReader");
        if (active) {
            reader = new MQAsyncReader[maxHandler];
            for (int i = 0; i < maxHandler; i++) {
                reader[i] = r;
                reader[i].start();
            }
        }
        else {
            System.out.println("start no active");
        }
    }

    public synchronized void stop() throws JMSException {
        for (int i = 0; i < reader.length; i++) {
            reader[i].stop();
        }
    }

    public static void main(String[] args) throws NamingException, JMSException{
        final Main main = new Main();
        Runtime.getRuntime().addShutdownHook(
            new Thread(
                new Runnable() {
                    public void run() {
                        try {
                            main.stop();
                        } catch (JMSException ex) {
                            ex.printStackTrace();
                        }
                    }
                }, "ShutdownHook"));
        main.start();
    }
}

Last make two configuration files in folder src. First named jndi.properties that used for JNDI configuration and the second named applicationContext.xml that used for Spring configuration file.

java.naming.factory.initial=org.apache.activemq.jndi.ActiveMQInitialContextFactory
java.naming.provider.url=tcp://localhost:61616

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
    <bean id="mqAsyncReader" class="com.ndung.mq.util.MQAsyncReader">
        <constructor-arg>
            <ref local="reqConfig" />
        </constructor-arg>
        <constructor-arg>
            <ref local="mqHandler" />
        </constructor-arg>
    </bean>
    <bean id="reqConfig" class="com.ndung.mq.util.MQConfig">
        <property name="queueName">
            <value>Q.REQUEST</value>
        </property>  
    </bean>
    <bean id="respConfig" class="com.ndung.mq.util.MQConfig">
        <property name="queueName">
            <value>Q.RESPONSE</value>
        </property>
        <property name="timeout">
            <value>20000</value>
        </property>
    </bean>
    <bean id="mqHandler" class="com.ndung.calc.server.MQHandler">
        <constructor-arg>
            <map>
                <entry key="+">
                    <bean class="com.ndung.calc.server.ProcessorAdd">
                    </bean>
            </map>
        </constructor-arg>
        <constructor-arg>
            <ref local="mqRespWriter" />
        </constructor-arg>
    </bean>
    <bean id="mqReqWriter" class="com.ndung.mq.util.MQWriter" init-method="init"
  destroy-method="terminate">
        <constructor-arg>
            <ref local="reqConfig" />
        </constructor-arg>        
    </bean>
    <bean id="mqRespSyncReader" class="com.ndung.mq.util.MQSyncReader" init-method="init"
  destroy-method="terminate">
        <constructor-arg>
            <ref local="respConfig" />
        </constructor-arg>
    </bean>    
    <bean id="client" class="com.ndung.calc.client.Client">
        <constructor-arg>
            <ref local="mqReqWriter"/>
        </constructor-arg>
        <constructor-arg>
            <ref local="mqRespSyncReader"/>
        </constructor-arg>        
    </bean>
    <bean id="mqRespWriter" class="com.ndung.mq.util.MQWriter" init-method="init"
  destroy-method="terminate">
        <constructor-arg>
            <ref local="respConfig" />
        </constructor-arg>        
    </bean>
</beans>

Run one instance of com.ndung.calc.server.Main, run and enter user inputs for several instance of com.ndung.calc.client.Main. Next post, introducing into MQ vendor that so many used in market and industry. It is MQSeries from IBM.

Read More..

Introduction to Message-oriented Middleware (MOM) and Java Messaging Service (JMS) Using Apache ActiveMQ

package com.ndung;

import javax.jms.*;
import org.apache.activemq.ActiveMQConnectionFactory;

public class HelloWorldProducer {
    public static void main(String[] args) throws JMSException {
        //Instantiate connection factory, specific to the vendor
        ActiveMQConnectionFactory connectionFactory = new ActiveMQConnectionFactory("vm://localhost");
        // Create a Connection
        Connection connection = connectionFactory.createConnection();
        connection.start();
        // Create a Session
        Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
        // Create the destination (Topic or Queue)
        Destination destination = session.createQueue("TEST.MQ");
        // Create a MessageProducer from the Session to the Topic or Queue
        MessageProducer producer = session.createProducer(destination);
        // Create a messages
        String text = "Hello world! From: ndung";
        TextMessage message = session.createTextMessage(text);
        // Tell the producer to send the message
        System.out.println("Message Sent");
        producer.send(message);
        // Clean up
        session.close();
        connection.close();
    }
}

package com.ndung;

import javax.jms.*;
import org.apache.activemq.ActiveMQConnectionFactory;

public class HelloWorldConsumer {
    public static void main(String[] args) throws JMSException {
        //Instantiate connection factory, specific to the vendor
        ActiveMQConnectionFactory connectionFactory = new ActiveMQConnectionFactory("vm://localhost");
        // Create a Connection
        Connection connection = connectionFactory.createConnection();
        connection.start();
        // Create a Session
        Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
        // Create the destination (Topic or Queue)
        Destination destination = session.createQueue("TEST.MQ");
        // Create a MessageConsumer from the Session to the Topic or Queue
        MessageConsumer consumer = session.createConsumer(destination);
        // Wait for a message
        Message message = consumer.receive(1000);
        if (message instanceof TextMessage) {
            TextMessage textMessage = (TextMessage) message;
            String text = textMessage.getText();
            System.out.println("Received: " + text);
        } else {
            System.out.println("Received: " + message);
        }
        consumer.close();
        session.close();
        connection.close();
    }
}

In the previous post, we have been introduced into EAI (Enterprise Application Integration) and a flash on Middleware. There are two fundamentally different types of middleware based on the approach used by the middleware to transfer the data between the distributed software applications. They are Remote Procedure Calls (RPC) based middleware and Message-oriented Middleware (MOM).
1. RPC. Software application that uses RPC based middleware to transfer data to another software application has to wait until the latter application is done processing the data. Thus, with this type of middleware, the communication proceeds in a lock step, synchronized manner, and the communicating processes are tightly coupled to one another. Examples of such middleware include Java RMI, CORBA, etc.
2. MOM. Is best described as a category of software for communication in an loosely-coupled, reliable, scalable, enabled asynchronous communication amongst distributed applications or systems.


JMS is a spesification that defines a set of interfaces and associated semantics, which allow applications written in Java to access the services of any JMS compliant Message MOM product. There are plenty of compliant MOM products available in market, including MQSeries from IBM, SonicMQ from Progress, Sun Java Message Queue, even Apache ActiveMQ, and many more.
The players in JMS:
1. Connections and Connection Factories
2. Sessions
3. Destinations
We should try first JMS First Impression using ActiveMQ in here. I'm using Netbeans 6.5 as IDE and prepare library: activemq-all-5.2.0.jar and jms.jar.

There are two different types of MOM: point-to-point and publish-and-subscribe.
1. Point-to-Point messaging style. In this model, a MOM is used by two applications to communicate with each other, often as an asynchronous replacement for remote procedure calls (RPC).
2. Publish-and-Subscribe messaging style. In this model multiple applications connect to the MOM as their publishers, which are producers of messages, or subscribers, which are consumers of messages. An important point of difference between the two styles is that a a point-to-point system is typically either a one-to-one system, which means one message sender talking to one message receiver, or it is a a many-to-one system, which means more than one senders are talking to one receiver. On the other hand, publish-and-subscribe systems are typically many-to-many systems, which means that there could be one or more publishers talking to one or more subscribers at a time.

Simple PTP (Point-to-Point) Application and Pub/Sub (Publisher and Subscriber) Application
We will enhance sample above by setting up activemq broker first and using JNDI. Configuring JNDI web application in Tomcat container can read in here. After we extract apache-activemq-5.2.0.rar that we have downloaded, edit activemq.xml that placed in folder conf. Delete all "multicast" in this configuration file. After that, enter folder bin, and run activemq. In the same project with above create packages named com.ndung.ptp and com.ndung.ps. Create new two java classes named SimpleQueueSender.java and SimpleQueueReceiver.java in com.ndung.ptp package and create new two java classes named SimpleTopicPublisher.java and SimpleTopicSubscriber in com.ndung.ps package.

package com.ndung.ptp;

import java.util.Properties;
import javax.jms.*;
import javax.naming.*;

public class SimpleQueueSender {
    public static void main(String[] args) throws NamingException, JMSException {
        String queueName = "PTP.ACTIVE.MQ";
        //setting JNDI configuration, differents between vendors.
        Properties props = new Properties();
        props.setProperty(Context.INITIAL_CONTEXT_FACTORY,
            "org.apache.activemq.jndi.ActiveMQInitialContextFactory");
        props.setProperty(Context.PROVIDER_URL,"tcp://localhost:61616");
        Context jndiContext = new InitialContext(props);
        ConnectionFactory queueConnectionFactory = (ConnectionFactory)
            jndiContext.lookup("ConnectionFactory");
        QueueConnection queueConnection = (QueueConnection)
            queueConnectionFactory.createConnection();
        QueueSession queueSession = queueConnection.createQueueSession(false,
            Session.AUTO_ACKNOWLEDGE);
        Queue queue = queueSession.createQueue(queueName);
        QueueSender queueSender = queueSession.createSender(queue);
        queueConnection.start();
        TextMessage textMessage = queueSession.createTextMessage();
        textMessage.setText("Hello World");
        queueSender.send(textMessage);
        queueSession.close();
        queueConnection.close();
    }
}

package com.ndung.ptp;

import java.util.Properties;
import javax.jms.*;
import javax.naming.*;

public class SimpleQueueReceiver {
    public static void main(String[] args) throws JMSException, NamingException {
        String queueName = "PTP.ACTIVE.MQ";
        //setting JNDI configuration, differents between vendors.
        Properties props = new Properties();
        props.setProperty(Context.INITIAL_CONTEXT_FACTORY,
            "org.apache.activemq.jndi.ActiveMQInitialContextFactory");
        props.setProperty(Context.PROVIDER_URL,"tcp://localhost:61616");
        Context jndiContext = new InitialContext(props);

        ConnectionFactory queueConnectionFactory = (ConnectionFactory)
            jndiContext.lookup("ConnectionFactory");
        QueueConnection queueConnection = (QueueConnection)
            queueConnectionFactory.createConnection();
        QueueSession queueSession = queueConnection.createQueueSession(false,
            Session.AUTO_ACKNOWLEDGE);
        Queue queue = queueSession.createQueue(queueName);
        QueueReceiver queueReceiver = queueSession.createReceiver(queue);
        queueConnection.start();
        TextMessage textMessage = (TextMessage) queueReceiver.receive();
        System.out.println(textMessage);
        queueSession.close();
        queueConnection.close();
    }
}

package com.ndung.ps;

import java.util.Properties;
import javax.jms.*;
import javax.naming.*;

public class SimpleTopicPublisher {
    public static void main(String[] args) throws Exception {
        try {
            Properties props = new Properties();
            props.setProperty(Context.INITIAL_CONTEXT_FACTORY,
                "org.apache.activemq.jndi.ActiveMQInitialContextFactory");
            props.setProperty(Context.PROVIDER_URL,"tcp://localhost:61616");
            Context jndiContext = new InitialContext(props);
            ConnectionFactory myConnectionFactory = (ConnectionFactory)
                jndiContext.lookup("ConnectionFactory");
            // Use myConnectionFactory to get a Topic connection
            TopicConnection myConnection = (TopicConnection)
                myConnectionFactory.createConnection();
            // Use myConnection to create a Topic session
            TopicSession mySession = myConnection.createTopicSession(false, 1);
            // Use mySession to get the Topic
            Topic myTopic = mySession.createTopic("PS.ACTIVE.MQ");
            // Use mySession to create a publisher for myTopic
            TopicPublisher myPublisher = mySession.createPublisher(myTopic);
            // Start the connection
            myConnection.start();
            // Create the HelloWorld message
            TextMessage m = mySession.createTextMessage();
            m.setText("Hello World");
            // Use myPublisher to publish the message
            myPublisher.publish(m);
            // Done.
            // Need to clean up
            mySession.close();
            myConnection.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

package com.ndung.ps;

import java.util.Properties;
import javax.jms.*;
import javax.naming.*;

public class SimpleTopicSubscriber {
    public static void main(String[] args) {
        try {
            Properties props = new Properties();
            props.setProperty(Context.INITIAL_CONTEXT_FACTORY,
                "org.apache.activemq.jndi.ActiveMQInitialContextFactory");
            props.setProperty(Context.PROVIDER_URL,"tcp://localhost:61616");
            Context jndiContext = new InitialContext(props);
            ConnectionFactory myConnectionFactory = (ConnectionFactory)
                jndiContext.lookup("ConnectionFactory");
            // Use myConnectionFactory to get a Topic connection
            TopicConnection myConnection = (TopicConnection)
                myConnectionFactory.createConnection();
            // Use myConnection to create a Topic session
            TopicSession mySession = myConnection.createTopicSession(false, 1);
            // Use mySession to get the Topic
            Topic myTopic = mySession.createTopic("PS.ACTIVE.MQ");
            // Use mySession to create a subscriber
            TopicSubscriber mySubscriber = mySession.createSubscriber(myTopic);
            // Start the connection
            myConnection.start();
            // Wait for the Hello World message
            // Use the receiver and wait forever until the message arrives
            TextMessage m = (TextMessage) mySubscriber.receive();
            // Display the message
            System.out.println("Received the message: " + m.getText());
            // Done.
            // Need to clean up
            mySession.close();
            myConnection.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

To know the differences between PTP application and Pub/Sub application:
1. Run two instance of SimpleQueueReceiver and then run one instance of SimpleQueueSender. One of SimpleQueueReceiver got message from SimpleQueueSender and the other one didn't.
2. Run two instance of SimpleTopicSubscriber and then run one instance of SimpleTopicPublisher. We can look both of SimpleTopicSubsriber got message from SimpleTopicPublisher.
We can monitor message queue by running http://localhost:8161/admin in web browser. More better coding style in the next post.

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Introduction to EAI

Enterprise Application Integration (EAI):

Imagine that a large company/project have more than one applications/softwares:
1. These applications run in different platforms, say for example: windows, linux, sun solaris, os/400, and so on.
2. Between these applications: from one application to another application must can communicate to each other. As example: for common case, one application need data from another application.
3. Message format for each applications are different. As example: One application uses EDI, another application uses XML, another application uses ISO8583 format, and so on.
4. Each application use different communication tools. As example: One application can use MQ, another application can use TCP/IP, another application use WebService, another application just can use HTTP, and so on.



EAI architecture must accommodate all transactions that need coordination from one application to another system application. EAI architecture must have characteristics as below:
1. A standard message format.
2. Middleware as communication channel.

Middleware must can handle following aspects:
1. Make sure message arrive at its destination.
2. Convert message from it's standard message format to other application message format and the other way.
3. Coordinate transaction.
4. Monitoring and logging.



EAI architecture components:
1. Adapter. EAI first implementation usually built by an adapter program for each application. This adapter will convert message from application's message format to middleware standard message format and other way.
2. Middleware also must have message router. This program will validate message and route message to appropriate destination.

Next material:
EAI Technology. EAI products as hub-and-spoke. Example of EAI products.
Taken from this material link.

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