Java Academy · Lesson

Implementation

Implement the REST API with entity, repository, service, and controller.

Lesson 2 of 48 steps

Implementation is a free Java Academy lesson on CoddyKit. This is lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Java Academy learning path, and your progress syncs across the web and the CoddyKit app. The Java Academy course includes 4 lessons in total.

Intro

Implementation: we now write code for entity, repository, service, and controller.

Code: Entity

The Task entity maps to a database table.

import jakarta.persistence.*;@Entity
public class Task {
  @Id @GeneratedValue
  private Long id;
  private String title;
  private boolean done;
  // getters/setters omitted
}

Code: Repository

The repository extends JpaRepository for CRUD operations.

import org.springframework.data.jpa.repository.JpaRepository;@Repository
public interface TaskRepository extends JpaRepository<Task, Long> {}

Code: Service

Service encapsulates business logic and uses the repository.

import org.springframework.stereotype.Service;import java.util.*;@Service
public class TaskService {
  private final TaskRepository repo;
  public TaskService(TaskRepository repo) { this.repo = repo; }
  public List<Task> all() { return repo.findAll(); }
  public Task save(Task t) { return repo.save(t); }
}

Code: Controller

The controller exposes endpoints using the service.

import org.springframework.web.bind.annotation.*;import java.util.*;@RestController
@RequestMapping("/tasks")
public class TaskController {
  private final TaskService service;
  public TaskController(TaskService service) { this.service = service; }
  @GetMapping public List<Task> all() { return service.all(); }
  @PostMapping public Task create(@RequestBody Task t) { return service.save(t); }
}

Run & test

Start app and test with curl: POST /tasks, GET /tasks.

Repository check

Quick check: Which Spring annotation is used to mark a repository interface?

Answer it in the interactive lesson

Recap

Recap: Implemented entity, repository, service, and controller to form the REST API.

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Frequently Asked Questions

Is the “Implementation” lesson free?

Yes — the full text of “Implementation” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Java Academy course, upgrade to CoddyKit PRO. The Java Academy course includes 4 lessons in total.

What will I learn in “Implementation”?

Implement the REST API with entity, repository, service, and controller. You practise Java Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Java Academy?

No prior experience is required. Java Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 2 of 4.

How long does the “Implementation” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Java Academy lesson?

Yes. Every Java Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

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