Request DTO for input in Spring Boot

Introduction

A Request DTO (Data Transfer Object) helps organize and carry data sent by users to your Spring Boot app in a simple, clear way.

When you want to receive user input in a clean, structured form.

When you need to validate user data before processing it.

When you want to separate input data from your business logic.

When building REST APIs that accept JSON or form data.

When you want to keep your controller methods simple and readable.

Syntax

Spring Boot

public class UserRequestDTO {
    private String name;
    private int age;

    // Getters and setters
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }

    public int getAge() { return age; }
    public void setAge(int age) { this.age = age; }
}

DTO classes usually have private fields with public getters and setters.

Spring Boot automatically converts JSON input to this DTO when used with @RequestBody.

Examples

A simple DTO for login data with username and password fields.

Spring Boot

public class LoginRequestDTO {
    private String username;
    private String password;

    // getters and setters
}

Using Java 17+ record to create an immutable DTO with less code.

Spring Boot

public record ProductRequestDTO(String name, double price) {}

DTO with validation annotations to check input rules automatically.

Spring Boot

public class RegisterRequestDTO {
    @NotBlank
    private String email;
    @Size(min = 6)
    private String password;

    // getters and setters
}

Sample Program

This example shows a simple DTO class UserRequestDTO and a Spring Boot controller that accepts JSON input mapped to this DTO. When you send a POST request with JSON like {"name":"Alice","age":30}, the controller returns a confirmation message.

Spring Boot

package com.example.demo.dto;

public class UserRequestDTO {
    private String name;
    private int age;

    public String getName() { return name; }
    public void setName(String name) { this.name = name; }

    public int getAge() { return age; }
    public void setAge(int age) { this.age = age; }
}

package com.example.demo.controller;

import com.example.demo.dto.UserRequestDTO;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserController {

    @PostMapping("/user")
    public String createUser(@RequestBody UserRequestDTO userRequest) {
        return "User " + userRequest.getName() + " aged " + userRequest.getAge() + " created.";
    }
}

Important Notes

Always keep DTOs simple and focused only on data transfer.

Use validation annotations to catch bad input early.

Spring Boot automatically maps JSON fields to DTO fields by name.

Summary

Request DTOs organize user input into simple classes.

They help keep your controller code clean and easy to read.

Spring Boot maps JSON input to DTOs automatically with @RequestBody.