How to Create a Simple Quarkus Project with Database Integration

Quarkus is a modern Java framework that is designed for building cloud-native applications. It offers fast startup times, low memory usage, and great developer productivity. In this tutorial, we will learn how to create a simple Quarkus project with database integration.

Step 1: Setting up the Development Environment

Before we start, we need to set up the development environment. You will need the following software installed:

• Java JDK 11 or later
• Apache Maven 3.6.2 or later

Step 2: Creating a New Quarkus Project

To create a new Quarkus project, open a command prompt or terminal window and navigate to the directory where you want to create the project. Then, run the following command:

mvn io.quarkus:quarkus-maven-plugin:2.3.2.Final:create \
    -DprojectGroupId=com.example \
    -DprojectArtifactId=quarkus-demo \
    -DclassName="com.example.GreetingResource" \
    -Dpath="/hello"

This command creates a new Quarkus project with a sample REST endpoint.

Step 3: Adding Database Integration

To add database integration, we need to add the following dependencies to the pom.xml file:

<dependency>
    <groupId>io.quarkus</groupId>
    <artifactId>quarkus-jdbc-postgresql</artifactId>
</dependency>
<dependency>
    <groupId>io.quarkus</groupId>
    <artifactId>quarkus-hibernate-orm-panache</artifactId>
</dependency>

These dependencies add support for the PostgreSQL database and the Panache ORM library.

Step 4: Configuring the Database Connection

Next, we need to configure the database connection. Open the application.properties file located in the src/main/resources directory and add the following lines:

quarkus.datasource.jdbc.url=jdbc:postgresql://localhost:5432/quarkus_demo
quarkus.datasource.username=postgres
quarkus.datasource.password=secret

Step 5: Creating a Data Entity

To store data in the database, we need to create a data entity. Create a new Java class in the src/main/java directory with the following code:

package com.example;

import javax.persistence.*;

@Entity
@Table(name = "persons")
public class Person {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "name")
    private String name;

    @Column(name = "age")
    private int age;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

This code defines a data entity called Person with three properties: id, name, and age. The @Entity annotation marks the class as a data entity and the @Table annotation specifies the database table name.

Step 6: Creating a Repository

To access the database, we need to create a repository. Create a new Java interface in the src/main/java directory with the following code:

package com.example;

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

public interface PersonRepository extends PanacheRepository<Person> {}

This code defines a repository interface called PersonRepository that extends the PanacheRepository interface from the Panache ORM library.

Step 7: Implementing the REST Endpoint

Now that we have set up the database integration, we can implement the REST endpoint. Open the GreetingResource.java file located in the src/main/java directory and replace the code with the following:

package com.example;

import javax.inject.Inject;
import javax.ws.rs.*;
import javax.ws.rs.core.MediaType;
import java.util.List;

@Path("/persons")
public class PersonResource {

  @Inject
  PersonRepository repository;

  @GET
  @Produces(MediaType.APPLICATION_JSON)
  public List<Person> list() {
    return repository.listAll();
  }

  @POST
  @Consumes(MediaType.APPLICATION_JSON)
  public void add(Person person) {
    repository.persist(person);
  }
}

This code defines a new REST endpoint at the /persons URL path. The endpoint has two methods: list() and add(). The list() method returns a list of all persons in the database, and the add() method adds a new person to the database.

Step 8: Testing the Application

To test the application, run the following command:

mvn compile quarkus:dev

This command compiles the application and starts a development mode with live reloading. Open a web browser and go to the http://localhost:8080/persons URL. You should see an empty JSON array. Use a tool like a curl or Postman to add a new person to the database:

curl -X POST \
     -H "Content-Type: application/json" \
     -d '{"name":"John Doe","age":30}' \
     http://localhost:8080/persons

Refresh the web browser, and you should see the newly added person in the JSON array.

Conclusion

In this tutorial, we learned how to create a simple Quarkus project with database integration. We added support for the PostgreSQL database and the Panache ORM library. We created a data entity, a repository, and a REST endpoint. Finally, we tested the application and verified that it worked as expected. Quarkus is a powerful framework that can help you build cloud-native applications quickly and efficiently.