A Spring Boot API

Controllers, validation and JSON are enough to ship a useful endpoint.

Beginner 15 min read Lesson 10 of 300 Challenge included

What you will be able to do

Use @RestController and @GetMapping for JSON endpoints.
Validate request records with Bean Validation.
Return 400 for invalid input and 404 for a missing resource.

In plain English

Spring Boot wires a servlet container and JSON serialization. A controller maps HTTP to a typed method. Validate input with annotations, return appropriate status codes and keep persistence in a service layer.

LessonController.javaJava

import org.springframework.web.bind.annotation.*;
import java.util.List;

@RestController
@RequestMapping("/api/lessons")
public class LessonController {
    private final LessonService service;

    public LessonController(LessonService service) {
        this.service = service;
    }

    @GetMapping
    public List<Lesson> list() {
        return service.published();
    }

    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public Lesson create(@RequestBody LessonInput input) {
        return service.create(input);
    }
}

Your turn

Add a GET endpoint

Medium

Create a controller with GET /api/health returning a map with ok = true.

JAVA · starter

@RestController
public class HealthController {}

Check your understanding before moving on.

Knowledge checkQuestion 1

Which annotation marks a class whose methods return JSON data?

Select an answer to continue

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Next: Drill 1: Summarise — Syntax and control flow

Lesson 10 of 300 · 0% of course