Falha no login, sou direcionado para a uma página http://localhost:8080/login?error e não efetuo login

Fiz os passos descritos na aula mas não consigo efetuar login de forma alguma. Sou direcionado a mesma página de login mas com um "?error". Não aparece nada no console, tanto do Eclipse quanto se eu usar o comando inspecionar do Chrome.

WebSecurityConfig

package br.com.alura.mvc.mudi.security;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
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.provisioning.InMemoryUserDetailsManager;

@Configuration
@EnableWebSecurity
public class WebSecurityConfig extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
        .authorizeRequests()
        .antMatchers("/css/**", "/js/**")
        .permitAll()
        .and()
        .authorizeRequests()
        .anyRequest()
        .authenticated()
        .and()
        .formLogin(
                form -> form
                        .loginPage("/login")
                        .permitAll()
        );

    }

    @Bean
    @Override
    protected UserDetailsService userDetailsService() {
        UserDetails user =
             User.withDefaultPasswordEncoder()
                .username("root")
                .password("root")
                .roles("ADM")
                .build();

        return new InMemoryUserDetailsManager(user);
    }
}

LoginController:

package br.com.alura.mvc.mudi.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class LoginController {

    @GetMapping
    @RequestMapping("/login")
    public String login() {
        return "login";
    }

}

<!DOCTYPE html>
<html>
    <head th:replace="~{base :: head}"></head>
    <body>
        <div th:replace="~{base :: logo}"></div>
        <div class="container">
            <div th:replace="~{base :: titulo('Login')}"></div>
            <div class="card mb-3">
                <form th:action="@{/login}" method="POST" class="card-body">
                    <div class="form-group mb-3">
                        <div class="mb-2">
                            <label for="username">Usuário</label>
                            <input name="username" class="form-control" placeholder="usuário"/>
                        </div>
                        <div class="mb-2">
                            <label for="password">Senha</label>
                            <input type="password" name="username" class="form-control" placeholder="senha"/>
                        </div>
                        <button class="btn btn-primary" type="submit">Login</button>
                    </div>                    
                </form>
            </div>
        </div>
    </body>
</html>

@GetMapping @RequestMapping("/login") public String login(HttpServletRequest request, Model model) { HttpSession session = request.getSession(false); String errorMessage = null; if (session != null) { AuthenticationException ex = (AuthenticationException) session .getAttribute(WebAttributes.AUTHENTICATION_EXCEPTION); if (ex != null) { errorMessage = ex.getMessage(); return "redirect:/login-error"; } } System.out.println("--->" + errorMessage); model.addAttribute("errorMessage", errorMessage); return "login"; }