# Getting Started to Quarkus Messaging with RabbitMQ

This guide demonstrates how your Quarkus application can utilize Quarkus Messaging to interact with RabbitMQ.

| This technology is considered preview. In preview, backward compatibility and presence in the ecosystem is not guaranteed. Specific improvements might require changing configuration or APIs, and plans to become stable are under way. Feedback is welcome on our mailing list or as issues in our GitHub issue tracker. For a full list of possible statuses, check our FAQ entry.

## Prerequisites

To complete this guide, you need:

- Roughly 15 minutes

- An IDE

- JDK 17+ installed with `JAVA_HOME` configured appropriately

- Apache Maven 3.9.9

- Docker and Docker Compose or Podman, and Docker Compose

- Optionally the Quarkus CLI if you want to use it

- Optionally Mandrel or GraalVM installed and configured appropriately if you want to build a native executable (or Docker if you use a native container build)

## Architecture

In this guide, we are going to develop two applications communicating with a RabbitMQ broker. The first application sends a quote request to the RabbitMQ quote requests exchange and consumes messages from the quote queue. The second application receives the quote request and sends a quote back.

The first application, the `producer`, will let the user request some quotes over an HTTP endpoint. For each quote request, a random identifier is generated and returned to the user, to put the quote request on pending. At the same time the generated request id is sent to the `quote-requests` exchange.

The second application, the `processor`, in turn, will read from the `quote-requests` queue put a random price to the quote, and send it to an exchange named `quotes`.

Lastly, the `producer` will read the quotes and send them to the browser using server-sent events. The user will therefore see the quote price updated from pending to the received price in real-time.

## Solution

We recommend that you follow the instructions in the next sections and create applications step by step. However, you can go right to the completed example.

Clone the Git repository: `git clone https://github.com/quarkusio/quarkus-quickstarts.git`, or download an archive.

The solution is located in the `rabbitmq-quickstart` directory.

## Creating the Maven Project

First, we need to create two projects: the producer and the processor.

To create the producer project, in a terminal run:

CLI

    quarkus create app org.acme:rabbitmq-quickstart-producer \
        --extension='messaging-rabbitmq,rest-jackson' \
        --no-code

To create a Gradle project, add the `--gradle` or `--gradle-kotlin-dsl` option.

For more information about how to install and use the Quarkus CLI, see the Quarkus CLI guide.

Maven

    mvn io.quarkus.platform:quarkus-maven-plugin:3.20.2.1:create \
        -DprojectGroupId=org.acme \
        -DprojectArtifactId=rabbitmq-quickstart-producer \
        -Dextensions='messaging-rabbitmq,rest-jackson' \
        -DnoCode

To create a Gradle project, add the `-DbuildTool=gradle` or `-DbuildTool=gradle-kotlin-dsl` option.

For Windows users:

- If using cmd, (don’t use backward slash `\` and put everything on the same line)

- If using Powershell, wrap `-D` parameters in double quotes e.g. `"-DprojectArtifactId=rabbitmq-quickstart-producer"`

This command creates the project structure and select the two Quarkus extensions we will be using:

1. The Reactive Messaging RabbitMQ connector

2. Quarkus REST (formerly RESTEasy Reactive) and its Jackson support to handle JSON payloads

| If you already have your Quarkus project configured, you can add the `messaging-rabbitmq` extension to your project by running the following command in your project base directory: CLI
    quarkus extension add messaging-rabbitmq
Maven
    ./mvnw quarkus:add-extension -Dextensions='messaging-rabbitmq'
Gradle
    ./gradlew addExtension --extensions='messaging-rabbitmq'
This will add the following to your `pom.xml`: pom.xml
    <dependency>
        <groupId>io.quarkus</groupId>
        <artifactId>quarkus-messaging-rabbitmq</artifactId>
    </dependency>
build.gradle
    implementation("io.quarkus:quarkus-messaging-rabbitmq")

To create the processor project, from the same directory, run:

CLI

    quarkus create app org.acme:rabbitmq-quickstart-processor \
        --extension='messaging-rabbitmq' \
        --no-code

To create a Gradle project, add the `--gradle` or `--gradle-kotlin-dsl` option.

For more information about how to install and use the Quarkus CLI, see the Quarkus CLI guide.

Maven

    mvn io.quarkus.platform:quarkus-maven-plugin:3.20.2.1:create \
        -DprojectGroupId=org.acme \
        -DprojectArtifactId=rabbitmq-quickstart-processor \
        -Dextensions='messaging-rabbitmq' \
        -DnoCode

To create a Gradle project, add the `-DbuildTool=gradle` or `-DbuildTool=gradle-kotlin-dsl` option.

For Windows users:

- If using cmd, (don’t use backward slash `\` and put everything on the same line)

- If using Powershell, wrap `-D` parameters in double quotes e.g. `"-DprojectArtifactId=rabbitmq-quickstart-processor"`

At that point you should have the following structure:

    .
    ├── rabbitmq-quickstart-processor
    │  ├── README.md
    │  ├── mvnw
    │  ├── mvnw.cmd
    │  ├── pom.xml
    │  └── src
    │     └── main
    │        ├── docker
    │        ├── java
    │        └── resources
    │           └── application.properties
    └── rabbitmq-quickstart-producer
       ├── README.md
       ├── mvnw
       ├── mvnw.cmd
       ├── pom.xml
       └── src
          └── main
             ├── docker
             ├── java
             └── resources
                └── application.properties

Open the two projects in your favorite IDE.

## The Quote object

The `Quote` class will be used in both `producer` and `processor` projects. For the sake of simplicity we will duplicate the class. In both projects, create the `src/main/java/org/acme/rabbitmq/model/Quote.java` file, with the following content:

    package org.acme.rabbitmq.model;

    import io.quarkus.runtime.annotations.RegisterForReflection;

    @RegisterForReflection
    public class Quote {

        public String id;
        public int price;

        /**
        * Default constructor required for Jackson serializer
        */
        public Quote() { }

        public Quote(String id, int price) {
            this.id = id;
            this.price = price;
        }

        @Override
        public String toString() {
            return "Quote{" +
                    "id='" + id + '\'' +
                    ", price=" + price +
                    '}';
        }
    }

JSON representation of `Quote` objects will be used in messages sent to the RabbitMQ queues and also in the server-sent events sent to browser clients.

Quarkus has built-in capabilities to deal with JSON RabbitMQ messages.

| @RegisterForReflection The `@RegisterForReflection` annotation instructs Quarkus to keep the class, its fields, and methods when creating a native executable. This is crucial when we later run our applications as native executables within containers. Without this annotation, the native compilation process would discard the fields and methods during the dead-code elimination phase, which would lead to runtime errors. More details about the `@RegisterForReflection` annotation can be found on the native application tips page.

## Sending quote request

Inside the `producer` project locate the generated `src/main/java/org/acme/rabbitmq/producer/QuotesResource.java` file, and update the content to be:

    package org.acme.rabbitmq.producer;

    import java.util.UUID;

    import jakarta.ws.rs.GET;
    import jakarta.ws.rs.POST;
    import jakarta.ws.rs.Path;
    import jakarta.ws.rs.Produces;
    import jakarta.ws.rs.core.MediaType;

    import org.acme.rabbitmq.model.Quote;
    import org.eclipse.microprofile.reactive.messaging.Channel;
    import org.eclipse.microprofile.reactive.messaging.Emitter;

    import io.smallrye.mutiny.Multi;

    @Path("/quotes")
    public class QuotesResource {

        @Channel("quote-requests") Emitter<String> quoteRequestEmitter; (1)

        /**
         * Endpoint to generate a new quote request id and send it to "quote-requests" channel (which
         * maps to the "quote-requests" RabbitMQ exchange) using the emitter.
         */
        @POST
        @Path("/request")
        @Produces(MediaType.TEXT_PLAIN)
        public String createRequest() {
            UUID uuid = UUID.randomUUID();
            quoteRequestEmitter.send(uuid.toString()); (2)
            return uuid.toString();
        }
    }

1 | Inject a Reactive Messaging `Emitter` to send messages to the `quote-requests` channel.
2 | On a post request, generate a random UUID and send it to the RabbitMQ queue using the emitter.

This channel is mapped to a RabbitMQ exchange using the configuration we will add to the `application.properties` file. Open the `src/main/resource/application.properties` file and add:

    # Configure the outgoing RabbitMQ exchange `quote-requests`
    mp.messaging.outgoing.quote-requests.connector=smallrye-rabbitmq
    mp.messaging.outgoing.quote-requests.exchange.name=quote-requests

All we need to specify is the `smallrye-rabbitmq` connector. By default, reactive messaging maps the channel name `quote-requests` to the same RabbitMQ exchange name.

## Processing quote requests

Now let’s consume the quote request and give out a price. Inside the `processor` project, locate the `src/main/java/org/acme/rabbitmq/processor/QuoteProcessor.java` file and add the following:

    package org.acme.rabbitmq.processor;

    import java.util.Random;

    import jakarta.enterprise.context.ApplicationScoped;

    import org.acme.rabbitmq.model.Quote;
    import org.eclipse.microprofile.reactive.messaging.Incoming;
    import org.eclipse.microprofile.reactive.messaging.Outgoing;

    import io.smallrye.reactive.messaging.annotations.Blocking;

    /**
     * A bean consuming data from the "quote-requests" RabbitMQ queue and giving out a random quote.
     * The result is pushed to the "quotes" RabbitMQ exchange.
     */
    @ApplicationScoped
    public class QuoteProcessor {

        private Random random = new Random();

        @Incoming("requests")       (1)
        @Outgoing("quotes")         (2)
        @Blocking                   (3)
        public Quote process(String quoteRequest) throws InterruptedException {
            // simulate some hard-working task
            Thread.sleep(1000);
            return new Quote(quoteRequest, random.nextInt(100));
        }
    }

1 | Indicates that the method consumes the items from the `requests` channel
2 | Indicates that the objects returned by the method are sent to the `quotes` channel
3 | Indicates that the processing is blocking and cannot be run on the caller thread.

The `process` method is called for every RabbitMQ message from the `quote-requests` queue, and will send a `Quote` object to the `quotes` exchange.

As with the previous example we need to configure the connectors in the `application.properties` file. Open the `src/main/resources/application.properties` file and add:

    # Configure the incoming RabbitMQ queue `quote-requests`
    mp.messaging.incoming.requests.connector=smallrye-rabbitmq
    mp.messaging.incoming.requests.queue.name=quote-requests
    mp.messaging.incoming.requests.exchange.name=quote-requests

    # Configure the outgoing RabbitMQ exchange `quotes`
    mp.messaging.outgoing.quotes.connector=smallrye-rabbitmq
    mp.messaging.outgoing.quotes.exchange.name=quotes

Note that in this case we have one incoming and one outgoing connector configuration, each one distinctly named. The configuration properties are structured as follows:

`mp.messaging.[outgoing|incoming].{channel-name}.property=value`

The `channel-name` segment must match the value set in the `@Incoming` and `@Outgoing` annotation:

- `quote-requests` → RabbitMQ queue from which we read the quote requests

- `quotes` → RabbitMQ exchange in which we write the quotes

## Receiving quotes

Back to our `producer` project. Let’s modify the `QuotesResource` to consume quotes, bind it to an HTTP endpoint to send events to clients:

    import io.smallrye.mutiny.Multi;
    //...

    @Channel("quotes") Multi<Quote> quotes;     (1)

    /**
     * Endpoint retrieving the "quotes" queue and sending the items to a server sent event.
     */
    @GET
    @Produces(MediaType.SERVER_SENT_EVENTS) (2)
    public Multi<Quote> stream() {
        return quotes; (3)
    }

1 | Injects the `quotes` channel using the `@Channel` qualifier
2 | Indicates that the content is sent using `Server Sent Events`
3 | Returns the stream (Reactive Stream)

Again we need to configure the incoming `quotes` channel inside `producer` project. Add the following inside `application.properties` file:

    # Configure the outgoing `quote-requests` queue
    mp.messaging.outgoing.quote-requests.connector=smallrye-rabbitmq

    # Configure the incoming `quotes` queue
    mp.messaging.incoming.quotes.connector=smallrye-rabbitmq

## The HTML page

Final touch, the HTML page reading the converted prices using SSE.

Create inside the `producer` project `src/main/resources/META-INF/resources/quotes.html` file, with the following content:

    <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Quotes</title>

        <link rel="stylesheet" type="text/css"
              href="https://cdnjs.cloudflare.com/ajax/libs/patternfly/3.24.0/css/patternfly.min.css">
        <link rel="stylesheet" type="text/css"
              href="https://cdnjs.cloudflare.com/ajax/libs/patternfly/3.24.0/css/patternfly-additions.min.css">
    </head>
    <body>
    <div class="container">
        <div class="card">
            <div class="card-body">
                <h2 class="card-title">Quotes</h2>
                <button class="btn btn-info" id="request-quote">Request Quote</button>
                <div class="quotes"></div>
            </div>
        </div>
    </div>
    </body>
    <script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
    <script>
        $("#request-quote").click((event) => {
            fetch("/quotes/request", {method: "POST"})
            .then(res => res.text())
            .then(qid => {
                var row = $(`<h4 class='col-md-12' id='${qid}'>Quote # <i>${qid}</i> | <strong>Pending</strong></h4>`);
                $(".quotes").append(row);
            });
        });
        var source = new EventSource("/quotes");
        source.onmessage = (event) => {
          var json = JSON.parse(event.data);
          $(`#${json.id}`).html(function(index, html) {
            return html.replace("Pending", `\$\xA0${json.price}`);
          });
        };
    </script>
    </html>

Nothing spectacular here. On each received quote, it updates the page.

## Get it running

You just need to run both applications using:

    mvn -f rabbitmq-quickstart-producer quarkus:dev

And, in a separate terminal:

    mvn -f rabbitmq-quickstart-processor quarkus:dev

Quarkus starts a RabbitMQ broker automatically, configures the application and shares the broker instance between different applications. See Dev Services for RabbitMQ for more details.

Open `http://localhost:8080/quotes.html` in your browser and request some quotes by clicking the button.

## Running in JVM or Native mode

When not running in dev or test mode, you will need to start your RabbitMQ broker. You can follow the instructions from the RabbitMQ Docker website or create a `docker-compose.yaml` file with the following content:

    version: '2'

    services:

      rabbit:
        image: rabbitmq:3.12-management
        ports:
          - "5672:5672"
        networks:
          - rabbitmq-quickstart-network

      producer:
        image: quarkus-quickstarts/rabbitmq-quickstart-producer:1.0-${QUARKUS_MODE:-jvm}
        build:
          context: rabbitmq-quickstart-producer
          dockerfile: src/main/docker/Dockerfile.${QUARKUS_MODE:-jvm}
        environment:
          RABBITMQ_HOST: rabbit
          RABBITMQ_PORT: 5672
        ports:
          - "8080:8080"
        networks:
          - rabbitmq-quickstart-network

      processor:
        image: quarkus-quickstarts/rabbitmq-quickstart-processor:1.0-${QUARKUS_MODE:-jvm}
        build:
          context: rabbitmq-quickstart-processor
          dockerfile: src/main/docker/Dockerfile.${QUARKUS_MODE:-jvm}
        environment:
          RABBITMQ_HOST: rabbit
          RABBITMQ_PORT: 5672
        networks:
          - rabbitmq-quickstart-network

    networks:
      rabbitmq-quickstart-network:
        name: rabbitmq-quickstart

Note how the RabbitMQ broker location is configured. The `rabbitmq-host` and `rabbitmq-port` (`AMQP_HOST` and `AMQP_PORT` environment variables) properties configure location.

First, make sure you stopped the applications, and build both applications in JVM mode with:

    mvn -f rabbitmq-quickstart-producer clean package
    mvn -f rabbitmq-quickstart-processor clean package

Once packaged, run `docker compose up --build`. The UI is exposed on http://localhost:8080/quotes.html

To run your applications as native, first we need to build the native executables:

    mvn -f rabbitmq-quickstart-producer package -Dnative  -Dquarkus.native.container-build=true
    mvn -f rabbitmq-quickstart-processor package -Dnative -Dquarkus.native.container-build=true

The `-Dquarkus.native.container-build=true` instructs Quarkus to build Linux 64bits native executables, who can run inside containers. Then, run the system using:

    export QUARKUS_MODE=native
    docker compose up --build

As before, the UI is exposed on http://localhost:8080/quotes.html

## Going further

This guide has shown how you can interact with RabbitMQ using Quarkus. It utilizes SmallRye Reactive Messaging to build data streaming applications.

If you did the Kafka, you have realized that it’s the same code. The only difference is the connector configuration and the JSON mapping.