DTO pattern for data transfer in Spring Boot - Mini Project: Build & Apply

DTO pattern for data transfer in Spring Boot

📖 Scenario: You are building a simple Spring Boot application to manage books in a library. You want to separate the data sent to clients from the internal data model by using a Data Transfer Object (DTO).

🎯 Goal: Create a Book DTO class and use it to transfer book data from the service layer to the controller layer in a Spring Boot application.

📋 What You'll Learn

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

Create a BookDTO class with fields title and author

Write a method to convert a Book entity to a BookDTO

Use the BookDTO in the controller to return book data

💡 Why This Matters

🌍 Real World

DTOs are used in real applications to control what data is sent over the network, improving security and flexibility.

💼 Career

Understanding DTOs is important for backend developers working with APIs and data transfer in Java Spring Boot projects.

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

Need a hint?

Define a simple Java class with private fields and public getter and setter methods.

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

Need a hint?

Create a simple Java class with only the fields you want to expose to clients.

3

Add a method to convert Book to BookDTO

Inside the BookDTO class, add a public static method called fromEntity 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;

    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 the fromEntity method below
}

Need a hint?

Create a static method that creates a new BookDTO and copies the title and author from the Book parameter.

4

Use BookDTO in the controller

In a Spring Boot controller class, write a method called getBookDTO that returns a BookDTO. Inside the method, create a Book object with id = 1L, title = "Spring Boot Guide", and author = "John Doe". Then return the result of BookDTO.fromEntity(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;
    }

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

// Add the controller method below

Need a hint?

Create a Spring Boot controller method that builds a Book and returns a BookDTO using the conversion method.