@Component, @Service, @Repository, @Controller in Spring Boot - Mini Project: Build & Apply

Using @Component, @Service, @Repository, and @Controller in Spring Boot

📖 Scenario: You are building a simple Spring Boot application to manage books in a library. You want to organize your code using Spring stereotypes to clearly separate responsibilities.

🎯 Goal: Learn how to use @Component, @Service, @Repository, and @Controller annotations to create a well-structured Spring Boot app.

📋 What You'll Learn

Create a class annotated with @Component for a utility helper

Create a class annotated with @Service to handle business logic

Create a class annotated with @Repository to simulate data access

Create a class annotated with @Controller to handle web requests

💡 Why This Matters

🌍 Real World

Organizing code in Spring Boot applications using stereotypes helps keep code clean and maintainable, making it easier to work on large projects with teams.

💼 Career

Understanding these annotations is essential for Java developers working with Spring Boot, as they are fundamental to building scalable and well-structured backend applications.

1

Create a utility class with @Component

Create a class called BookHelper annotated with @Component inside package com.example.library.util. This class will have a method formatTitle(String title) that returns the title in uppercase.

Spring Boot

package com.example.library.util;

import org.springframework.stereotype.Component;

// Your code here

Need a hint?

Use @Component above the class declaration to mark it as a Spring component.

2

Create a service class with @Service

Create a class called BookService annotated with @Service inside package com.example.library.service. Add a method getBookCount() that returns the integer 5.

Spring Boot

package com.example.library.service;

import org.springframework.stereotype.Service;

// Your code here

Need a hint?

Use @Service above the class declaration to mark it as a service layer component.

3

Create a repository class with @Repository

Create a class called BookRepository annotated with @Repository inside package com.example.library.repository. Add a method findAll() that returns a List<String> with these exact book titles: "Spring Basics", "Java Fundamentals".

Spring Boot

package com.example.library.repository;

import org.springframework.stereotype.Repository;
import java.util.List;
import java.util.Arrays;

// Your code here

Need a hint?

Use @Repository above the class declaration to mark it as a data access component.

4

Create a controller class with @Controller

Create a class called BookController annotated with @Controller inside package com.example.library.controller. Add a method showBooks() annotated with @GetMapping("/books") that returns the string "books".

Spring Boot

package com.example.library.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;

// Your code here

Need a hint?

Use @Controller above the class and @GetMapping("/books") above the method to handle web requests.