Messaging

package at.aydin.lab.messaging.legacy;

import javax.jms.Connection;
import javax.jms.ConnectionFactory;
import javax.jms.MessageConsumer;
import javax.jms.MessageProducer;
import javax.jms.Queue;
import javax.jms.Session;
import javax.jms.TextMessage;

// Design Pattern: Messaging Gateway
// Zweck: JMS-Infrastruktur wird hinter einfachen Sende-/Empfangsmethoden gekapselt.
public final class LegacyJmsGateway {
    private final ConnectionFactory connectionFactory;
    public LegacyJmsGateway(ConnectionFactory connectionFactory) {
        this.connectionFactory = connectionFactory;
    }

    public void send(String queueName, String payload) throws Exception {
        try (Connection connection = connectionFactory.createConnection(); Session session = connection.createSession(false,
            Session.AUTO_ACKNOWLEDGE)) {
            Queue queue = session.createQueue(queueName);
            try (MessageProducer producer = session.createProducer(queue)) {
                producer.send(session.createTextMessage(payload));
            }
        }
    }

    public String receive(String queueName, long timeoutMillis) throws Exception {
        try (Connection connection = connectionFactory.createConnection(); Session session = connection.createSession(false,
            Session.AUTO_ACKNOWLEDGE)) {
            connection.start();
            Queue queue = session.createQueue(queueName);
            try (MessageConsumer consumer = session.createConsumer(queue)) {
                return ((TextMessage) consumer.receive(timeoutMillis)).getText();
            }
        }
    }
}

package at.aydin.lab.messaging.modern;

import org.springframework.jms.core.JmsTemplate;
import org.springframework.stereotype.Component;

@Component
// Design Pattern: Messaging Gateway
// Zweck: Fachcode muss weder Connection noch Session verwalten.
public class OrderMessagePublisher {
    private final JmsTemplate jmsTemplate;
    public OrderMessagePublisher(JmsTemplate jmsTemplate) {
        this.jmsTemplate = jmsTemplate;
    }

    public void publish(String orderNumber) {
        jmsTemplate.convertAndSend("orders", orderNumber);
    }
}

package at.aydin.lab.messaging.modern;

import org.springframework.jms.annotation.JmsListener;
import org.springframework.stereotype.Component;

@Component
// Design Pattern: Message-Driven Consumer
// Zweck: Nachrichten werden ereignisorientiert verarbeitet.
public class OrderMessageListener {
    @JmsListener(destination = "orders")
    public void receive(String orderNumber) {
        System.out.println("Empfangen: " + orderNumber);
    }
}

package at.aydin.lab.messaging.legacy;

import org.apache.activemq.ActiveMQConnectionFactory;
import org.apache.activemq.broker.BrokerService;

public final class MessagingLegacyApplication {
    private MessagingLegacyApplication() {
    }

    public static void main(String[] args) throws Exception {
        BrokerService broker = new BrokerService();
        broker.setBrokerName("legacy-demo");
        broker.setPersistent(false);
        broker.addConnector("vm://legacy-demo");
        broker.start();
        try {
            LegacyJmsGateway gateway = new LegacyJmsGateway(new ActiveMQConnectionFactory("vm://legacy-demo?create=false"));
            gateway.send("orders", "ORDER-1001");
            System.out.println("Empfangen: " + gateway.receive("orders", 2000));
        } finally {
            broker.stop();
        }
    }
}

package at.aydin.lab.messaging.modern;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class MessagingModernApplication {
    public static void main(String[] args) {
        SpringApplication.run(MessagingModernApplication.class, args);
    }
}

package at.aydin.lab.messaging.modern;

import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;

@Component
public class MessageDemoRunner implements CommandLineRunner {
    private final OrderMessagePublisher publisher;
    public MessageDemoRunner(OrderMessagePublisher publisher) {
        this.publisher = publisher;
    }

    @Override
    public void run(String ... args) {
        publisher.publish("ORDER-2001");
    }
}