Hello World

Description

In this simple HelloWorld example, We will create a Sender program that sends messages to a queue and we will create a Reciever program that picks the messages from a queue and consumes it.

Requirements

• JDK 17+
• RabbitMQ on Docker

Install RabbitMQ on Docker

docker-compose.yml:

version: '3'

services:
  rabbitmq:
    image: rabbitmq:management
    container_name: rabbitmq
    environment:
      - RABBITMQ_DEFAULT_USER=admin
      - RABBITMQ_DEFAULT_PASS=admin
    ports:
      - "5672:5672"
      - "15672:15672"

networks:
  default:
    driver: bridge

Open the URL: http://localhost:15672/

username: admin
password: admin

Project Structure

.
├── pom.xml
├── README.md
└── src
    └── main
        └── java
            └── com
                └── jreact
                    └── rabbitmq
                        ├── Reciever.java
                        └── Sender.java

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>rabbitmq-hello-world</groupId>
    <artifactId>rabbitmq-hello-world</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    <properties>
        <main.class>com.jreact.rabbitmq.${mc}</main.class>
    </properties>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/com.rabbitmq/amqp-client -->
        <dependency>
            <groupId>com.rabbitmq</groupId>
            <artifactId>amqp-client</artifactId>
            <version>5.20.0</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-api -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>2.0.13</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-simple -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-simple</artifactId>
            <version>2.0.13</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <defaultGoal>install</defaultGoal>
        <finalName>${mc}</finalName>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.5.1</version>
                <inherited>true</inherited>
                <configuration>
                    <source>17</source>
                    <target>17</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-assembly-plugin</artifactId>
                <version>3.6.0</version>
                <configuration>
                    <descriptorRefs>
                        <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                    <archive>
                        <manifest>
                            <mainClass>${main.class}</mainClass>
                        </manifest>
                    </archive>
                </configuration>
                <executions>
                    <execution>
                        <id>make-assembly</id>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

Reciever.java

package com.jreact.rabbitmq;

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.DeliverCallback;

public class Reciever {
	private final static String QUEUE_NAME = "hello";

	public static void main(String[] argv) throws Exception {
		ConnectionFactory factory = new ConnectionFactory();
		factory.setHost("localhost");
		factory.setUsername("admin");
		factory.setPassword("admin");
		Connection connection = factory.newConnection();
		Channel channel = connection.createChannel();

		channel.queueDeclare(QUEUE_NAME, false, false, false, null);
		System.out.println(" [*] Waiting for messages. To exit press CTRL+C");

		DeliverCallback deliverCallback = (consumerTag, delivery) -> {
			String message = new String(delivery.getBody(), "UTF-8");
			System.out.println(" [x] Received '" + message + "'");
		};
		channel.basicConsume(QUEUE_NAME, true, deliverCallback, consumerTag -> {
		});
	}
}

Sender.java

package com.jreact.rabbitmq;

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

public class Sender {
	private final static String QUEUE_NAME = "hello";

	public static void main(String[] argv) throws Exception {
		ConnectionFactory factory = new ConnectionFactory();
		factory.setHost("localhost");
		factory.setUsername("admin");
		factory.setPassword("admin");
		try (Connection connection = factory.newConnection(); Channel channel = connection.createChannel()) {
			channel.queueDeclare(QUEUE_NAME, false, false, false, null);

			for (int i = 0; i < 10; i++) {
				String message = "Hello World! " + i;
				channel.basicPublish("", QUEUE_NAME, null, message.getBytes("UTF-8"));
				System.out.println(" [x] Sent '" + message + "'");
			}
		}
	}
}

Running

mvn package -Dmc=Reciever
mvn package -Dmc=Sender

goto target

Make new terminal

java -jar Reciever-jar-with-dependencies.jar

SLF4J(W): No SLF4J providers were found.
SLF4J(W): Defaulting to no-operation (NOP) logger implementation
SLF4J(W): See https://www.slf4j.org/codes.html#noProviders for further details.
 [*] Waiting for messages. To exit press CTRL+C

Make next terminal

java -jar Sender-jar-with-dependencies.jar

SLF4J(W): No SLF4J providers were found.
SLF4J(W): Defaulting to no-operation (NOP) logger implementation
SLF4J(W): See https://www.slf4j.org/codes.html#noProviders for further details.
 [x] Sent 'Hello World! 0'
 [x] Sent 'Hello World! 1'
 [x] Sent 'Hello World! 2'
 [x] Sent 'Hello World! 3'
 [x] Sent 'Hello World! 4'
 [x] Sent 'Hello World! 5'
 [x] Sent 'Hello World! 6'
 [x] Sent 'Hello World! 7'
 [x] Sent 'Hello World! 8'
 [x] Sent 'Hello World! 9'

goto Reciever terminal

SLF4J(W): No SLF4J providers were found.
SLF4J(W): Defaulting to no-operation (NOP) logger implementation
SLF4J(W): See https://www.slf4j.org/codes.html#noProviders for further details.
 [*] Waiting for messages. To exit press CTRL+C
 [x] Received 'Hello World! 0'
 [x] Received 'Hello World! 1'
 [x] Received 'Hello World! 2'
 [x] Received 'Hello World! 3'
 [x] Received 'Hello World! 4'
 [x] Received 'Hello World! 5'
 [x] Received 'Hello World! 6'
 [x] Received 'Hello World! 7'
 [x] Received 'Hello World! 8'
 [x] Received 'Hello World! 9'

---

Source Code:
https://github.com/ZbCiok/zjc-examples/tree/main/reactive-messaging/rabbitmq/rabbitmq-hello-world