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Creating a Quarkus REST API: Hands-On

In this tutorial, we will create a Quakus REST API with Java.

Prerequisites

I am using the version 3.1.0.Final.

Creating the Quarkus application

Let's create our API with quarkus CLI:

quarkus create app com.github.platformoon:platformoon-api

  • com.github.platformoon is the groupId.

  • platformoon-api is the artifactId.

Running our API

Go to the platformoon-api directory.

And execute:

quarkus dev

The output should looks something like this:

 --/ __ \/ / / / _ | / _ \/ //_/ / / / __/ 
 -/ /_/ / /_/ / __ |/ , _/ ,< / /_/ /\ \   
--\___\_\____/_/ |_/_/|_/_/|_|\____/___/   
2023-10-27 21:28:54,604 INFO  [io.quarkus] (Quarkus Main Thread) platformoon-api 1.0.0-SNAPSHOT on JVM (powered by Quarkus 3.5.0) started in 1.742s. Listening on: http://localhost:8080

2023-10-27 21:28:54,608 INFO  [io.quarkus] (Quarkus Main Thread) Profile dev activated. Live Coding activated.
2023-10-27 21:28:54,608 INFO  [io.quarkus] (Quarkus Main Thread) Installed features: [cdi, resteasy-reactive, smallrye-context-propagation, vertx]

If you access your browser at: http://localhost:8008/hello, you will get a response from the API.

Installing RESTEasy Reactive Jackson

Let's install Jackson to get support for JSON Serialisation:

quarkus ext add io.quarkus:quarkus-resteasy-reactive-jackson

Creating the Resource

com.github.platformoon.presentation.resource.ApplicationResource
package com.github.platformoon.presentation.resource;

import java.net.URI;
import java.util.UUID;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.github.platformoon.presentation.resource.request.CreateApplicationRequest;

import jakarta.ws.rs.POST;
import jakarta.ws.rs.Path;
import jakarta.ws.rs.core.Response;

@Path("/applications")
@Consumes(MediaType.APPLICATION_JSON)
@Produces(MediaType.APPLICATION_JSON)
public class ApplicationResource {

    private static final Logger LOGGER = LoggerFactory.getLogger(ApplicationResource.class);

    @POST
    public Response createApplicationHandler(final CreateApplicationRequest request) {
        LOGGER.info("createApplicationHandler: {}", request);

        return Response
            .created(
                URI.create("/applications/" + UUID.randomUUID().toString()))
            .build();
    }
}

Creating the DTO

com.github.platformoon.presentation.resource.request.CreateApplicationRequest
package com.github.platformoon.presentation.resource.request;

public record CreateApplicationRequest(String name, String technology) {}

Testing the resource

Execute the application with quarkus dev and make a request to the new endpoint:

curl -v --request POST \
  --url http://localhost:8080/applications \
  --header 'Content-Type: application/json' \
  --data '{
    "name": "application",
    "technology": "JAVA",
    "type": "API"
}'

We can observe the response header 'Location' containing the resource URI. If we check the Quarkus log, we may find something like this:

2023-10-27 22:09:29,646 INFO  [com.git.pla.pre.res.ApplicationResource] (executor-thread-1) createApplicationHandler: CreateApplicationRequest[name=application, technology=JAVA, type=API]

Done

Let's return to the Platformoon CLI and implement an HTTP call to this new endpoint. Go to the Calling REST API using GoLang tutorial.