DTO vs entity separation benefit in Spring Boot - Hands-On Comparison

Understanding DTO vs Entity Separation in Spring Boot

📖 Scenario: You are building a simple Spring Boot application to manage books in a library. You want to keep your data organized and safe when sending information between the client and the server.

🎯 Goal: Learn how to separate the data transfer object (DTO) from the entity class to protect your database structure and control what data is shared.

📋 What You'll Learn

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

Create a BookDTO class with fields title and author only

Write a method to convert a Book entity to a BookDTO

Write a method to convert a BookDTO back to a Book entity

💡 Why This Matters

🌍 Real World

In real apps, separating DTOs from entities helps protect your database details and control exactly what data clients see.

💼 Career

Understanding DTO vs entity separation is important for backend developers working with Spring Boot to build secure and maintainable APIs.

1

Create the Book entity class

Create a class called Book with private fields Long id, String title, and String author. Include public getters and setters for each field.

Spring Boot

// Your code here to create the Book entity class with id, title, and author fields

Need a hint?

Think of the Book class as the real data stored in your database. It needs an id to identify each book uniquely.

2

Create the BookDTO class

Create a class called BookDTO with private fields String title and String author. Include public getters and setters for each field.

Spring Boot

public class Book {
    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 to create the BookDTO class with title and author fields

Need a hint?

The BookDTO class is like a simple package that only carries the book's title and author to the client, hiding the database id.

3

Add method to convert Book entity to BookDTO

Add a public static method called fromEntity inside the BookDTO class. It takes a Book object as a parameter and returns a new BookDTO with the title and author copied from the Book.

Spring Boot

public class Book {
    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;
    }
}

public class BookDTO {
    private String title;
    private String author;

    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;
    }

    // Add fromEntity method below
    // Your code here
}

Need a hint?

This method helps you create a safe copy of the book data to send outside your app, without exposing the database id.

4

Add method to convert BookDTO to Book entity

Add a public method called toEntity inside the BookDTO class. It returns a new Book object with the title and author copied from the BookDTO. The id should not be set here.

Spring Boot

public class Book {
    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;
    }
}

public class BookDTO {
    private String title;
    private String author;

    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;
    }

    public static BookDTO fromEntity(Book book) {
        BookDTO dto = new BookDTO();
        dto.setTitle(book.getTitle());
        dto.setAuthor(book.getAuthor());
        return dto;
    }

    // Add toEntity method below
    // Your code here
}

Need a hint?

This method lets you create a new Book entity from the data received from the client, without setting the database id.