Why REST controllers are essential in Spring Boot - See It in Action

Why REST controllers are essential

📖 Scenario: You are building a simple web service for a bookstore. You want to let users see the list of books and add new books through the web.

🎯 Goal: Create a REST controller in Spring Boot that handles HTTP requests to get all books and add a new book. This will show why REST controllers are essential for connecting your backend logic to the web.

📋 What You'll Learn

Create a list of books as initial data

Add a configuration variable for the base URL path

Write a REST controller class with methods to handle GET and POST requests

Use Spring Boot annotations to map URLs and HTTP methods

💡 Why This Matters

🌍 Real World

REST controllers are essential in web applications to expose backend services as APIs that frontend apps or other services can use.

💼 Career

Understanding REST controllers is key for backend developers working with Spring Boot to build scalable and maintainable web services.

1

Create initial book data

Create a List<String> called books with these exact entries: "Spring Boot Basics", "RESTful APIs", "Java Programming".

Spring Boot

# Create a List called books with 3 book titles
# Your code here

Need a hint?

Use List.of() to create an immutable list with the given book titles.

2

Add base URL path configuration

Create a String variable called basePath and set it to "/api/books".

Spring Boot

List books = List.of("Spring Boot Basics", "RESTful APIs", "Java Programming");
# Create a String variable basePath with value "/api/books"
# Your code here

Need a hint?

This string will be used as the base URL path for the REST controller.

3

Create REST controller class with GET and POST methods

Create a public class called BookController annotated with @RestController and @RequestMapping(basePath). Inside it, write a method getBooks() annotated with @GetMapping that returns the books list. Also, add a method addBook(String book) annotated with @PostMapping that returns a string "Added: " + book.

Spring Boot

List books = List.of("Spring Boot Basics", "RESTful APIs", "Java Programming");
String basePath = "/api/books";

// Create BookController class with @RestController and @RequestMapping(basePath)
// Add getBooks() method with @GetMapping returning books
// Add addBook(String book) method with @PostMapping returning "Added: " + book
# Your code here

Need a hint?

Use Spring Boot annotations to map the class and methods to HTTP requests. The @RequestBody annotation is needed to get the POST request body.

4

Complete REST controller setup

Add the necessary import statements for List and org.springframework.web.bind.annotation.RequestBody at the top of the file to complete the REST controller code.

Spring Boot

import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
// Add import for java.util.List and org.springframework.web.bind.annotation.RequestBody

@RestController
@RequestMapping("/api/books")
public class BookController {
    List books = List.of("Spring Boot Basics", "RESTful APIs", "Java Programming");

    @GetMapping
    public List getBooks() {
        return books;
    }

    @PostMapping
    public String addBook(@RequestBody String book) {
        return "Added: " + book;
    }
}
# Your code here

Need a hint?

Import statements are needed for the List type and the @RequestBody annotation.