Why DTOs matter in Spring Boot - See It in Action

Why DTOs Matter in Spring Boot

📖 Scenario: You are building a simple Spring Boot application to manage books in a library. You want to send only necessary book information to users, not the entire database entity. This helps keep your app safe and efficient.

🎯 Goal: Build a Spring Boot project that uses a Book entity and a BookDTO (Data Transfer Object) to send limited book data to the client.

📋 What You'll Learn

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

Create a BookDTO class with only title and author fields

Write a method to convert a Book entity to a BookDTO

Use the BookDTO in a controller method to return book data

💡 Why This Matters

🌍 Real World

In real apps, DTOs help control what data is sent over the network, improving security and performance.

💼 Career

Understanding DTOs is essential for backend developers working with APIs and data transfer in Spring Boot applications.

1

Create the Book entity class

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

Spring Boot

// Your code here to create the Book class with fields and getters/setters

Need a hint?

Think of the Book class as a container holding all details about a book. Use private fields and public getters/setters to follow Java best practices.

2

Create the BookDTO class

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

Spring Boot

public class Book {
    private Long id;
    private String title;
    private String author;
    private double price;

    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 double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }
}

// Your code here to create the BookDTO class with title and author fields and getters/setters

Need a hint?

The BookDTO class holds only the data you want to share. It is like a smaller package with just the title and author.

3

Add a method to convert Book to BookDTO

Inside the BookDTO class, add a public static method called fromBook that 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;
    private double price;

    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 double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }
}

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 the fromBook method below
    // Your code here

Need a hint?

This method helps convert a full Book into a smaller BookDTO. Think of it as packing only what you want to send.

4

Use BookDTO in a controller method

Create a Spring Boot controller class called BookController with a method getBookDTO that returns a BookDTO. Inside the method, create a Book object with title "Spring Boot Guide" and author "Jane Doe". Use the BookDTO.fromBook method to convert and return the DTO.

Spring Boot

public class Book {
    private Long id;
    private String title;
    private String author;
    private double price;

    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 double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }
}

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

// Your code here to create BookController with getBookDTO method

Need a hint?

The controller sends only the BookDTO to the client. This keeps your app safe by hiding the price and id.