JpaRepository interface in Spring Boot - Mini Project: Build & Apply

Using JpaRepository Interface in Spring Boot

📖 Scenario: You are building a simple Spring Boot application to manage a list of books in a library. You want to store book data in a database and use Spring Data JPA to handle database operations easily.

🎯 Goal: Create a Spring Boot repository interface using JpaRepository to manage Book entities. You will set up the entity, configure the repository interface, and use it to perform basic database operations.

📋 What You'll Learn

Create a Book entity class with id, title, and author fields

Create a repository interface called BookRepository that extends JpaRepository

Use the repository interface to find all books

Add a method to find books by author name

💡 Why This Matters

🌍 Real World

Spring Data JPA repositories simplify database access in real-world Java applications by providing ready-made methods and easy ways to add custom queries.

💼 Career

Knowing how to use JpaRepository is essential for Java backend developers working with Spring Boot to build efficient and maintainable data access layers.

1

Create the Book entity class

Create a Java class called Book annotated with @Entity. Add private fields Long id, String title, and String author. Annotate id with @Id and @GeneratedValue. Include public getters and setters for all fields.

Spring Boot

@Entity
public class Book {
    // Your code here
}

Need a hint?

Use @Entity to mark the class as a database entity. Use @Id and @GeneratedValue on the id field. Add getters and setters for all fields.

2

Create the BookRepository interface

Create a public interface called BookRepository that extends JpaRepository<Book, Long>. This interface will allow Spring Data JPA to provide basic database operations for Book entities.

Spring Boot

import jakarta.persistence.Entity;
import jakarta.persistence.Id;
import jakarta.persistence.GeneratedValue;

@Entity
public class Book {
    @Id
    @GeneratedValue
    private Long id;
    private String title;
    private String author;

    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 String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }
}

// Your code here

Need a hint?

Extend JpaRepository with the entity Book and its ID type Long.

3

Add method to find all books

Inside the BookRepository interface, add a method declaration List<Book> findAll() to retrieve all books from the database.

Spring Boot

import jakarta.persistence.Entity;
import jakarta.persistence.Id;
import jakarta.persistence.GeneratedValue;

@Entity
public class Book {
    @Id
    @GeneratedValue
    private Long id;
    private String title;
    private String author;

    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 String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }
}

import org.springframework.data.jpa.repository.JpaRepository;
import java.util.List;

public interface BookRepository extends JpaRepository {
    // Add method to find all books
    // Your code here
}

Need a hint?

Declare the method List<Book> findAll() inside the interface. JpaRepository already provides this method, but declaring it explicitly helps understanding.

4

Add method to find books by author

Add a method declaration List<Book> findByAuthor(String author) inside the BookRepository interface. This method will allow finding all books by a specific author.

Spring Boot

import jakarta.persistence.Entity;
import jakarta.persistence.Id;
import jakarta.persistence.GeneratedValue;

@Entity
public class Book {
    @Id
    @GeneratedValue
    private Long id;
    private String title;
    private String author;

    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 String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }
}

import org.springframework.data.jpa.repository.JpaRepository;
import java.util.List;

public interface BookRepository extends JpaRepository {
    List findAll();
    // Add method to find books by author
    // Your code here
}

Need a hint?

Use Spring Data JPA's method naming convention to create findByAuthor method that takes a String author parameter.