🌐 Build a Todo REST API 🔥🔥🔥

Let’s take your Spring Boot skills to the next level by building a fully functional REST API — no frontend, no database, just clean, JSON-speaking HTTP endpoints using in-memory data.

✅ What You’ll Build

A Todo API with endpoints like:


GET    /api/todos         → list all todos
GET    /api/todos/{id}    → get a single todo
POST   /api/todos         → create a new todo
PUT    /api/todos/{id}    → update an existing todo
DELETE /api/todos/{id}    → delete a todo

🛠️ Step 1: Create a Todo Model

In src/main/java/com/example/demo/, create:

Todo.java

package com.example.demo;

public class Todo {
    private Long id;
    private String title;
    private boolean completed;

    public Todo() {}

    public Todo(Long id, String title, boolean completed) {
        this.id = id;
        this.title = title;
        this.completed = completed;
    }

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

    public String getTitle() { return title; }
    public void setTitle(String title) { this.title = title; }

    public boolean isCompleted() { return completed; }
    public void setCompleted(boolean completed) { this.completed = completed; }
}

🛠️ Step 2: Create the TodoController

Add your REST API endpoints:

TodoController.java

package com.example.demo;

import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

import java.util.*;

@RestController
@RequestMapping("/api/todos")
public class TodoController {

    private final Map<Long, Todo> todos = new HashMap<>();
    private long nextId = 1;

    @GetMapping
    public ResponseEntity<List<Todo>> getAllTodos() {
        return ResponseEntity.ok(new ArrayList<>(todos.values()));
    }

    @GetMapping("/{id}")
    public ResponseEntity<Todo> getTodoById(@PathVariable Long id) {
        Todo todo = todos.get(id);
        return todo != null ? ResponseEntity.ok(todo)
                            : ResponseEntity.notFound().build();
    }

    @PostMapping
    public ResponseEntity<Todo> createTodo(@RequestBody Todo newTodo) {
        newTodo.setId(nextId++);
        todos.put(newTodo.getId(), newTodo);
        return ResponseEntity.ok(newTodo);
    }

    @PutMapping("/{id}")
    public ResponseEntity<Todo> updateTodo(@PathVariable Long id, @RequestBody Todo updatedTodo) {
        if (!todos.containsKey(id)) {
            return ResponseEntity.notFound().build();
        }
        updatedTodo.setId(id);
        todos.put(id, updatedTodo);
        return ResponseEntity.ok(updatedTodo);
    }

    @DeleteMapping("/{id}")
    public ResponseEntity<Void> deleteTodo(@PathVariable Long id) {
        return todos.remove(id) != null
            ? ResponseEntity.noContent().build()
            : ResponseEntity.notFound().build();
    }
}

🧪 Step 3: Test Your API

Use curl, Postman, or VS Code REST Client.

✅ Create a Todo

curl -X POST http://localhost:8080/api/todos \
  -H "Content-Type: application/json" \
  -d '{"title": "Write guide", "completed": false}'

📋 Get All Todos

curl http://localhost:8080/api/todos

✏️ Update a Todo

curl -X PUT http://localhost:8080/api/todos/1 \
  -H "Content-Type: application/json" \
  -d '{"title": "Finish REST guide", "completed": true}'

❌ Delete a Todo

curl -X DELETE http://localhost:8080/api/todos/1

💡 Outcome