In this tutorial, we are going to see an example for Spring Boot RabbitMQ Message Publishing.

Spring Boot RabbitMQ Message Publishing:

As part of this example, we will be sending JSON messages to RabbitMQ queue.

Prerequisites:

• Install RabbitMQ on your machine. If you haven’t installed yet, you can follow my previous tutorial to install RabbitMQ on windows operating system.
• Start RabbitMQ server on your machine.

Technologies:

• Spring Boot 2.1.4 RELEASE
• Spring Boot Started AMQP
• RabbitMQ 3.7.15
• Lombok
• Java8
• Maven

1 Project Structure:

2 Project Dependencies:

<dependencies>
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-amqp</artifactId>
  </dependency>
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
  </dependency>
  <dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <optional>true</optional>
  </dependency>
</dependencies>

3. RabbitMQ properties:

Configuring RabbitMQ server URL, port, username and password details in application.properties file.

spring.rabbitmq.host=localhost
spring.rabbitmq.port=5672
spring.rabbitmq.username=guest
spring.rabbitmq.password=guest

4. Item Model:

Creating Item model class, representing the Item JSON message. Which will be sent to RabbitMQ queue.

package com.onlinetutorialspoint.model;

import com.fasterxml.jackson.annotation.JsonIdentityInfo;
import com.fasterxml.jackson.annotation.ObjectIdGenerators;
import lombok.Data;
import lombok.NoArgsConstructor;

@JsonIdentityInfo(generator = ObjectIdGenerators.IntSequenceGenerator.class,property = "@id",scope = Item.class)
@Data
@NoArgsConstructor
public class Item {
    private String itemName;
    private String category;
    private String description;
}

5. RabbitMQ configurations:

Creating a RabbitMQ config class with all necessary beans to get RabbitMq queue, exchange, and routing key.

package com.onlinetutorialspoint.config;

import org.springframework.amqp.core.*;
import org.springframework.amqp.rabbit.connection.ConnectionFactory;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.amqp.support.converter.Jackson2JsonMessageConverter;
import org.springframework.amqp.support.converter.MessageConverter;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class RabbitMQConfig {

    private String QUEUE="items-queue";

    private String EXCHANGE="otp-exchange";

    private String ROUTING_KEY="items";
    @Bean
    Queue queue() {
        return new Queue(QUEUE, true);
    }
    @Bean
    DirectExchange exchange() {
        return new DirectExchange(EXCHANGE);
    }

    @Bean
    Binding binding(Queue queue, DirectExchange exchange) {
        return BindingBuilder.bind(queue).to(exchange).with(ROUTING_KEY);
    }
    @Bean
    public MessageConverter jsonMessageConverter() {
        return new Jackson2JsonMessageConverter();
    }

    @Bean
    public AmqpTemplate amqpTemplate(ConnectionFactory connectionFactory) {
        final RabbitTemplate rabbitTemplate = new RabbitTemplate(connectionFactory);
        rabbitTemplate.setMessageConverter(jsonMessageConverter());
        return rabbitTemplate;
    }
}

AmqpTemplate specifies a basic set of AMQP operations; it provides synchronous send and receives messages.

If you are going to send/receive messages in the form of POJOs, it should be expected to delegate to an instance of MessageConverter to perform the conversion from AMQP byte[] payload type.

6. RabbitMQ Service:

Creating RabbitMQService class which is responsible for sending messages on RabbitMQ queue using AmqpTemplate.

package com.onlinetutorialspoint.service;

import com.onlinetutorialspoint.model.Item;
import org.springframework.amqp.core.AmqpTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class RabbitMqService {
    @Autowired
    private AmqpTemplate amqpTemplate;

    private String EXCHANGE="otp-exchange";

    private String ROUTING_KEY="items";

    public void sendMessage(Item item) {
        amqpTemplate.convertAndSend(EXCHANGE, ROUTING_KEY, item);
    }
}

The convertAndSend() methods allow you to send POJO objects.

7. Rest Controller:

Creating RabbitMqController class having one post method to post Item message on RabbitMQ.

package com.onlinetutorialspoint.controller;

import com.onlinetutorialspoint.model.Item;
import com.onlinetutorialspoint.service.RabbitMqService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class RabbitMqController {
    @Autowired
    RabbitMqService rabbitMqService;

    @PostMapping("/items")
    public ResponseEntity<String> postMessage(@RequestBody Item item){
        rabbitMqService.sendMessage(item);
        return new ResponseEntity<String>("Item pushed to RabbitMQ",HttpStatus.CREATED);
    }
}

8. Main-Class:

package com.onlinetutorialspoint;

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

@SpringBootApplication
public class SpringBootRabbitMqProducerApplication {

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

}

9. Run It:

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.1.4.RELEASE)

2019-06-05 21:10:05.250  INFO 8388 --- [           main] .o.SpringBootRabbitMqProducerApplication : Starting SpringBootRabbitMqProducerApplication on DESKTOP-RN4SMHT with PID 8388 (D:\work\Spring-Boot-RabbitMQ-Producer\target\classes started by Lenovo in D:\work\Spring-Boot-RabbitMQ-Producer)
2019-06-05 21:10:05.250  INFO 8388 --- [           main] .o.SpringBootRabbitMqProducerApplication : No active profile set, falling back to default profiles: default
2019-06-05 21:10:09.172  INFO 8388 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
.....
.....

Accessing the application through localhost:8080/items from the postman and sending a POST request.

10. Verify in RabbitMQ:

Login to RabbitMQ management console http://localhost:15672

Goto Queues click on the queue which you configured and expand the Messages; there you can see the messages like below.

References:

• Install RabbitMQ on Windows
• RabbitMQ Queue

Download Source from GIT:

Happy Learning 🙂