Custom query methods by naming convention in Spring Boot - Mini Project: Build & Apply

Custom Query Methods by Naming Convention in Spring Boot

📖 Scenario: You are building a simple Spring Boot application to manage a list of books in a library. You want to find books by their title and by their author using Spring Data JPA's custom query methods by naming convention.

🎯 Goal: Create a Spring Data JPA repository interface with custom query methods that find books by their exact title and by their author's name.

📋 What You'll Learn

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

Create a repository interface called BookRepository that extends JpaRepository.

Add a custom query method findByTitle to find a book by its exact title.

Add a custom query method findByAuthor to find all books by a given author.

💡 Why This Matters

🌍 Real World

Finding data by specific fields is common in applications like libraries, stores, or user management systems. Spring Data JPA lets you write simple method names to get this functionality without writing SQL.

💼 Career

Knowing how to create custom query methods by naming convention is a key skill for Java backend developers working with Spring Boot and databases.

1

Create the Book entity

Create a class called Book with private fields Long id, String title, and String author. Annotate it with @Entity and mark id as the primary key with @Id and @GeneratedValue.

Spring Boot

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

Need a hint?

Use @Entity on the class, @Id and @GeneratedValue on the id field.

2

Create the BookRepository interface

Create an interface called BookRepository that extends JpaRepository<Book, Long>.

Spring Boot

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.GeneratedValue;

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

    // Getters and setters
    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<Book, Long> in the interface declaration.

3

Add custom query method to find by title

Inside the BookRepository interface, add a method declaration Book findByTitle(String title); to find a book by its exact title.

Spring Boot

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.GeneratedValue;

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

    // Getters and setters
    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;

public interface BookRepository extends JpaRepository {
    // Your code here
}

Need a hint?

Use the method name findByTitle with a String title parameter.

4

Add custom query method to find by author

Inside the BookRepository interface, add a method declaration List<Book> findByAuthor(String author); to find all books by the given author. Import java.util.List.

Spring Boot

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.GeneratedValue;

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

    // Getters and setters
    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;

public interface BookRepository extends JpaRepository {
    Book findByTitle(String title);
    // Your code here
}

Need a hint?

Use List<Book> as the return type and import java.util.List.