Validation groups in Spring Boot - Mini Project: Build & Apply

Using Validation Groups in Spring Boot

📖 Scenario: You are building a simple user registration system where different validation rules apply depending on whether the user is registering or updating their profile.

🎯 Goal: Create a Spring Boot application that uses validation groups to apply different validation rules for user registration and user update operations.

📋 What You'll Learn

Create a User class with fields username, email, and password

Define two validation groups: RegisterGroup and UpdateGroup

Apply validation annotations to User fields with groups

Create a controller method that validates User using the RegisterGroup

Create a controller method that validates User using the UpdateGroup

💡 Why This Matters

🌍 Real World

Validation groups let you reuse the same data model but apply different rules depending on the action, like registration or update forms.

💼 Career

Understanding validation groups is important for backend developers working with Spring Boot to build robust APIs with flexible validation.

1

Create the User class with fields

Create a class called User with three private fields: username of type String, email of type String, and password of type String. Include public getters and setters for each field.

Spring Boot

public class User {
    // Your code here
}

Need a hint?

Define private fields and generate public getter and setter methods for each.

2

Define validation groups interfaces

Create two empty interfaces called RegisterGroup and UpdateGroup in the same package as User. These will be used as validation groups.

Spring Boot

public interface RegisterGroup {
    // Your code here
}

public interface UpdateGroup {
    // Your code here
}

Need a hint?

Interfaces for validation groups are empty marker interfaces.

3

Add validation annotations with groups to User fields

In the User class, add validation annotations with groups: annotate username with @NotBlank(groups = RegisterGroup.class), annotate email with @Email(groups = {RegisterGroup.class, UpdateGroup.class}), and annotate password with @NotBlank(groups = RegisterGroup.class). Import necessary validation annotations.

Spring Boot

import jakarta.validation.constraints.Email;
import jakarta.validation.constraints.NotBlank;

public class User {
    // Add validation annotations with groups here
    private String username;
    private String email;
    private String password;

    // getters and setters
}

// RegisterGroup and UpdateGroup interfaces remain unchanged

Need a hint?

Use @NotBlank and @Email annotations with the groups attribute to specify validation groups.

4

Create controller methods validating with groups

Create a Spring REST controller class called UserController. Add two methods: registerUser and updateUser. Both accept a @RequestBody User user. Annotate registerUser parameter with @Validated(RegisterGroup.class) and updateUser parameter with @Validated(UpdateGroup.class). Both methods return String confirming success.

Spring Boot

import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;

@RestController
public class UserController {
    // Add registerUser method here

    // Add updateUser method here
}

Need a hint?

Use @Validated(Group.class) on method parameters to apply validation groups.