Spring Security 6 & JWT Authentication · Aula

Implementação personalizada de UserDetailsService

Crie um `UserDetailsService` personalizado para carregar dados específicos de usuários do armazenamento de dados da sua aplicação durante a autenticação.

Implementação personalizada de UserDetailsService é uma aula grátis de Spring Security 6 & JWT Authentication no CoddyKit. Esta é a aula 1 de 4. Você pode ler a aula completa abaixo gratuitamente — depois pratica ao vivo no navegador com um editor de código integrado e um tutor de IA 24/7. Faz parte do caminho de aprendizado de Spring Security 6 & JWT Authentication, e seu progresso é sincronizado entre a web e o app CoddyKit. O curso de Spring Security 6 & JWT Authentication inclui 4 aulas no total.

Partes desta aula ainda não foram traduzidas e aparecem em inglês.

Beyond In-Memory Users

In previous lessons, you might have used in-memory users for simple authentication. This means usernames and passwords are hardcoded directly in your application's configuration.

While easy for testing, real-world applications need to load user data from a persistent source like a database, LDAP, or another service. This is where a custom UserDetailsService comes in!

The UserDetailsService Interface

Spring Security uses the UserDetailsService interface to retrieve user-specific data during authentication. It has just one method you need to implement:

UserDetails loadUserByUsername(String username)

This method is crucial. When a user tries to log in, Spring Security calls this method, passing the username provided by the user.

What is UserDetails?

The loadUserByUsername method must return a UserDetails object. This interface represents the authenticated user's information, including:

Username
Password
Authorities (roles/permissions)
Account status (e.g., enabled, locked, expired)

Spring Security provides a default implementation called org.springframework.security.core.userdetails.User that you'll often use.

Creating Your Custom Service

To create a custom user service, you simply create a class that implements UserDetailsService. Inside, you'll override the loadUserByUsername method.

This method is where you'll write the logic to fetch user data from your chosen data store. For now, we'll use some hardcoded examples.

Implementing loadUserByUsername

Inside loadUserByUsername, you'll perform these steps:

Receive the username.
Look up the user in your data source.
If found, create a UserDetails object with their details (username, password, roles).
If not found, throw a UsernameNotFoundException.

Remember, password encoding is vital for security, but we'll cover that in a later lesson. For now, we'll use a plain text password prefix: {noop}.

Code: Basic UserDetailsService

Let's see a simple implementation. This example hardcodes users, simulating fetching from a data source. Run it to see how it works!

import org.springframework.security.core.userdetails.User;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.core.userdetails.UsernameNotFoundException;
import java.util.Arrays;
import java.util.Collections;

class MyUserDetailsService implements UserDetailsService {
    @Override
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
        // In a real app, you'd fetch user from a database
        if ("user".equals(username)) {
            return User.withUsername("user")
                       .password("{noop}password") // {noop} for plain text
                       .roles("USER")
                       .build();
        }
        if ("admin".equals(username)) {
            return User.withUsername("admin")
                       .password("{noop}adminpass")
                       .roles("ADMIN", "USER")
                       .build();
        }
        throw new UsernameNotFoundException("User not found: " + username);
    }
}

public class Main {
    public static void main(String[] args) {
        MyUserDetailsService service = new MyUserDetailsService();

        System.out.println("Attempting to load 'user'...");
        try {
            UserDetails user = service.loadUserByUsername("user");
            System.out.println("Loaded User: " + user.getUsername());
            System.out.println("Authorities: " + user.getAuthorities());
        } catch (UsernameNotFoundException e) {
            System.out.println(e.getMessage());
        }

        System.out.println("\nAttempting to load 'admin'...");
        try {
            UserDetails admin = service.loadUserByUsername("admin");
            System.out.println("Loaded Admin: " + admin.getUsername());
            System.out.println("Authorities: " + admin.getAuthorities());
        } catch (UsernameNotFoundException e) {
            System.out.println(e.getMessage());
        }

        System.out.println("\nAttempting to load 'unknown'...");
        try {
            service.loadUserByUsername("unknown");
        } catch (UsernameNotFoundException e) {
            System.out.println(e.getMessage());
        }
    }
}

Adding Roles and Authorities

Notice in the example, we used .roles("USER") and .roles("ADMIN", "USER").

Roles are high-level permissions, like 'ADMIN' or 'USER'.
These roles are converted into GrantedAuthority objects by Spring Security.
When building the UserDetails object, you specify the roles/authorities the user possesses.

These authorities are later used by Spring Security for authorization (determining what a user can access).

Registering Your Service

Once you've created your custom UserDetailsService, Spring Security needs to know about it. In a Spring Boot application, you typically register it as a Spring bean.

By simply defining your custom service as a @Bean, Spring Security's auto-configuration will usually pick it up and use it for authentication.

The Custom Authentication Flow

Here's how custom authentication typically works with your service:

User submits login credentials (username, password).
Spring Security receives the request.
It calls your custom UserDetailsService's loadUserByUsername() method with the provided username.
Your method fetches user data and returns a UserDetails object.
Spring Security then compares the provided password with the password from UserDetails (after encoding/decoding).
If they match, authentication succeeds!

Check Your Understanding

Consider the core purpose and components of implementing a custom UserDetailsService.

Recap: Custom UserDetailsService

You've learned how to implement a custom UserDetailsService, a fundamental component for advanced user authentication in Spring Security:

It allows loading user data from any source.
You implement the loadUserByUsername method.
This method returns a UserDetails object, containing user credentials and authorities.
It's essential for moving beyond in-memory user management.

Next, we'll dive into securing those passwords with proper encoding!

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Crie um `UserDetailsService` personalizado para carregar dados específicos de usuários do armazenamento de dados da sua aplicação durante a autenticação. Você pratica Spring Security 6 & JWT Authentication com código prático que executa diretamente no navegador, e um tutor de IA 24/7 responde suas dúvidas enquanto trabalha na aula.

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Todas as aulas deste curso

Implementação personalizada de UserDetailsService
Entendendo codificadores de senhas
Integração do gerenciamento de usuários com banco de dados
Autorização baseada em funções com Granted Authorities

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