Quarkus Famework Cheatsheet

Quarkus is a revolutionary framework that empowers developers to build highly efficient, cloud-native applications with Java. Its innovative approach to ahead-of-time (AOT) compilation, native image generation, and seamless integration with popular Java libraries make it a game-changer in the world of microservices and cloud-native development. In this cheatsheet, we’ll explore key concepts and code snippets to help you leverage the full potential of Quarkus.

1. Getting Started

1.1 Installing Quarkus

Use the following command to install Quarkus using the Maven plugin:

mvn io.quarkus:quarkus-maven-plugin:2.7.5.Final:create \
    -DprojectGroupId=com.example \
    -DprojectArtifactId=my-quarkus-project \
    -DclassName="com.example.GreetingResource" \
    -Dpath="/hello"

1.2 Running Quarkus Application

Execute the following command to start your Quarkus application in development mode:

./mvnw quarkus:dev

2. RESTful Endpoints

2.1 Creating a REST Endpoint

Define a simple REST endpoint with the @Path and @GET annotations:

import javax.ws.rs.GET;
import javax.ws.rs.Path;

@Path("/hello")
public class GreetingResource {

    @GET
    public String hello() {
        return "Hello, Quarkus!";
    }
}

3. Dependency Injection

3.1 Injecting Dependencies

Quarkus supports CDI (Contexts and Dependency Injection). Inject a bean using @Inject:

import javax.inject.Inject;

public class MyService {

    @Inject
    GreetingService greetingService;

    // Your code here
}

4. Persistence with Panache

4.1 Creating an Entity

Define a JPA entity using Panache:

import io.quarkus.hibernate.orm.panache.PanacheEntity;

@Entity
public class Book extends PanacheEntity {

    public String title;
    public String author;
}

4.2 CRUD Operations

Perform CRUD operations using Panache:

// Create
Book.persist(new Book("Quarkus Guide", "John Doe"));

// Read
List<Book> books = Book.listAll();

// Update
Book book = Book.findById(id);
book.title = "Updated Title";
book.persist();

// Delete
Book.deleteById(id);

5. Testing

5.1 Unit Testing

Write unit tests with Quarkus Test:

import io.quarkus.test.junit.QuarkusTest;
import org.junit.jupiter.api.Test;

@QuarkusTest
public class GreetingResourceTest {

    @Test
    public void testHelloEndpoint() {
        given()
          .when().get("/hello")
          .then()
             .statusCode(200)
             .body(is("Hello, Quarkus!"));
    }
}

6. Configuring Quarkus

6.1 Application Configuration

Configure your application using the application.properties file:

# application.properties

quarkus.datasource.url=jdbc:h2:mem:mydatabase
quarkus.datasource.driver=org.h2.Driver
quarkus.hibernate-orm.database.generation=update

Quarkus is a powerful and flexible framework that simplifies and accelerates Java development for cloud-native applications. This cheatsheet provides a quick reference for essential Quarkus features, helping you streamline your development process. Experiment with these code snippets and explore the extensive documentation to fully harness the capabilities of Quarkus in your projects.

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