Project structure walkthrough in Spring Boot - Mini Project: Build & Apply

Spring Boot Project Structure Walkthrough

📖 Scenario: You are starting a new Spring Boot application for a simple book catalog. Understanding the project structure helps you organize your code and files properly.

🎯 Goal: Build the basic Spring Boot project structure with main application class, a controller package, and a simple REST controller.

📋 What You'll Learn

Create the main application class with the correct package and annotation

Add a configuration variable for the base API path

Create a REST controller class inside the controller package

Add a simple GET endpoint that returns a welcome message

💡 Why This Matters

🌍 Real World

Spring Boot is widely used to build backend services and APIs. Understanding the project structure helps you organize code for maintainability and scalability.

💼 Career

Knowing how to set up and navigate Spring Boot projects is essential for Java backend developer roles.

1

Create the main Spring Boot application class

Create a package called com.example.bookcatalog. Inside it, create a class named BookCatalogApplication annotated with @SpringBootApplication. Add the main method that runs SpringApplication.run(BookCatalogApplication.class, args).

Spring Boot

package com.example.bookcatalog;

// Your code here

Need a hint?

The main class must be in the base package and annotated with @SpringBootApplication. The main method starts the app.

2

Add a configuration variable for the base API path

Inside the BookCatalogApplication class, add a public static final String variable named BASE_API_PATH and set it to "/api/books".

Spring Boot

package com.example.bookcatalog;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class BookCatalogApplication {
    public static void main(String[] args) {
        SpringApplication.run(BookCatalogApplication.class, args);
    }

    // Add a public static final String BASE_API_PATH = "/api/books" here
}

Need a hint?

This variable will hold the base path for your API endpoints.

3

Create a REST controller class inside the controller package

Create a new package com.example.bookcatalog.controller. Inside it, create a class named BookController annotated with @RestController. Import the annotation from org.springframework.web.bind.annotation.RestController.

Spring Boot

package com.example.bookcatalog.controller;

// Your code here

Need a hint?

The controller class handles HTTP requests. Use @RestController to mark it.

4

Add a simple GET endpoint that returns a welcome message

Inside BookController, add a method named welcome annotated with @GetMapping(BookCatalogApplication.BASE_API_PATH). The method returns a String with the text "Welcome to the Book Catalog!". Import @GetMapping from org.springframework.web.bind.annotation.GetMapping.

Spring Boot

package com.example.bookcatalog.controller;

import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.bind.annotation.GetMapping;

@RestController
public class BookController {

    // Add a method with @GetMapping(BookCatalogApplication.BASE_API_PATH) that returns "Welcome to the Book Catalog!"
}

Need a hint?

This method handles GET requests at the base API path and returns a welcome message.