authorizeRequest()弃用后Spring Boot Security自定义登录页失效问题

我尝试用自定义Thymeleaf登录页替换Spring Boot Security的默认登录页，但未达到预期效果，反而弹出「需要授权」的提示。以下是弃用authorizeRequest()和antMatchers()后的相关代码：

安全配置代码 #

@EnableWebSecurity
@Configuration
public class HospitalSecurityConfig {

    @Bean
    public SecurityFilterChain filterChain (HttpSecurity http) throws Exception {
        
        http
        
        .authorizeHttpRequests()
        .requestMatchers("/").authenticated()
        .requestMatchers("/mylogin").permitAll()
        .and()
        .formLogin().loginPage("/mylogin").loginProcessingUrl("/mylogin").permitAll()
        .and()
        .logout().logoutUrl("/logout")
        .and()
        .authenticationProvider(authProvider())
        .httpBasic()
        ;
        
        return http.build();
        
    }
    
    @Bean
    public UserDetailsService detailsService() {
        
        return new HospitalUserDetailsServiceer();
    }

    @Bean
    public AuthenticationProvider authProvider() {
        DaoAuthenticationProvider provider = new DaoAuthenticationProvider();
        provider.setPasswordEncoder(encoder());
        provider.setUserDetailsService(detailsService());
                
                return provider;
    }

    @Bean
    public PasswordEncoder encoder() {
        
        return new BCryptPasswordEncoder();
    }
}

myLogin.html代码 #

<!DOCTYPE html>
<html  xmlns="http://www.w3.org/1999/xhtml"
    xmlns:th="http://www.thymeleaf.org" 
    xmlns:sec="http://www.thymeleaf.org/thymeleaf-extras-springsecurity3"
    xmlns:layout="http://www.ultraq.net.nz/thymeleaf/layout">
<head>
<meta charset="ISO-8859-1">
<title>Welcome to HealthMe Application!</title>
 <link th:href="@{/css/cssLogin.css}" rel="stylesheet" />
 <script type="text/javascript" th:src="@{/js/jsLogin.js}"></script>
 </head>
<body>

<form th:action="@{/mylogin}" method="post">

Username = <input name="username" type="text"> <br>
Password = <input name="password" type="password"> <br>
<input type="submit">
</form>

</body>
</html>

MVC配置代码 #

@EnableWebMvc
@Configuration
public class HospitalMVCconfig implements WebMvcConfigurer{

    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
        registry.addViewController("/mylogin").setViewName("myLogin");
    }
}

内容的提问来源于stack exchange，提问作者Saman KHATAEI