Service calling repository in Spring Boot - Mini Project: Build & Apply

Service Calling Repository in Spring Boot

📖 Scenario: You are building a simple Spring Boot application to manage books in a library. The application needs to store book information and retrieve it when requested.In this project, you will create a repository to hold book data and a service that calls this repository to get the list of books.

🎯 Goal: Build a Spring Boot service class that calls a repository class to fetch a list of books.This will help you understand how services and repositories work together in Spring Boot.

📋 What You'll Learn

Create a repository class with a method to return a list of book titles

Create a service class that calls the repository method

Use dependency injection to connect the service and repository

Return the list of books from the service method

💡 Why This Matters

🌍 Real World

In real applications, services call repositories to separate business logic from data access. This pattern helps keep code organized and easier to maintain.

💼 Career

Understanding how to connect services and repositories with Spring annotations is essential for backend development roles using Spring Boot.

1

Create the BookRepository class with a method to get books

Create a class called BookRepository with a method getBooks() that returns a List<String> containing exactly these book titles: "Spring Basics", "Java Fundamentals", "REST APIs".

Spring Boot

public class BookRepository {
    // Your code here
}

Need a hint?

Use Arrays.asList to create the list of book titles inside the getBooks() method.

2

Add a service class with a repository field

Create a class called BookService with a private field bookRepository of type BookRepository. Add a constructor that takes a BookRepository parameter and assigns it to the bookRepository field.

Spring Boot

import java.util.List;

public class BookService {
    // Your code here
}

Need a hint?

Use constructor injection to assign the bookRepository field.

3

Add a method in BookService to call the repository

In the BookService class, add a public method getAllBooks() that returns a List<String>. Inside this method, call bookRepository.getBooks() and return its result.

Spring Boot

import java.util.List;

public class BookService {
    private BookRepository bookRepository;

    public BookService(BookRepository bookRepository) {
        this.bookRepository = bookRepository;
    }

    // Add getAllBooks() method here
}

Need a hint?

Call the repository method inside the service method and return the list.

4

Add Spring annotations to connect service and repository

Add the @Repository annotation to the BookRepository class and the @Service annotation to the BookService class. Also, add the @Autowired annotation to the constructor of BookService to enable dependency injection.

Spring Boot

@Repository
public class BookRepository {
    public List getBooks() {
        return Arrays.asList("Spring Basics", "Java Fundamentals", "REST APIs");
    }
}

@Service
public class BookService {
    private BookRepository bookRepository;

    @Autowired
    public BookService(BookRepository bookRepository) {
        this.bookRepository = bookRepository;
    }

    public List getAllBooks() {
        return bookRepository.getBooks();
    }
}

Need a hint?

Use Spring annotations @Repository, @Service, and @Autowired to connect the classes.