Manage User Redirect Spring Security - spring-boot

Question

i'm new to spring security can any one guide me how to do this. my configuration class of spring security is mention below: i made my home page "/" visible to all user. so i didn't use "/" in http.antmatchs("/") in home page my nav bar has link for "login and signup". after successful login user redirect to "buyer/list" endpoint which i mention in configuration. what i want is "login user" can't visit homepage again. for this i also use
Object principal = SecurityContextHolder.getContext().getAuthentication().getPrincipal();
for "/" mapping controller, but it throw nullPointerException. can any one guide me how do i proceed. if there is other approach please mention.
Configuration
#EnableWebSecurity
public class SecureConfig extends WebSecurityConfigurerAdapter {
#Autowired
UserDetailsService userDetailsService;
#Value("${winni.auth.exit}")
private String authExit;
#Override
protected void configure(AuthenticationManagerBuilder auth) throws Exception {
auth.userDetailsService(userDetailsService)
.passwordEncoder(passwordEncoder());
}
#Override
protected void configure(HttpSecurity http) throws Exception {
http.requestMatchers()
.antMatchers("/login", "/web/**", "/action/**", "/cart/**", "/cart/xhr/**", "/buyer/**","/profile/**","/chat/**","/order/**")
.and()
.authorizeRequests()
.anyRequest().authenticated()
.and()
.formLogin().loginPage("/login").defaultSuccessUrl("/buyer/list", true).permitAll().and()
.logout().logoutSuccessUrl(authExit);
}
#Bean
public PasswordEncoder passwordEncoder() {
return new BCryptPasswordEncoder();
}
#Override
public void configure(WebSecurity web) throws Exception {
web.ignoring().antMatchers("/assets/**");
}
}

Answer 1

So you want that only unauthenticated users can access "/" and "/login" and only authenticated users on the other pages. I would do something like this:
http
.authorizeRequests()
.antMatchers("/web/**", "/action/**", "/cart/**", "/cart/xhr/**", "/buyer/**","/profile/**","/chat/**","/order/**")
.authenticated()
.and()
.antMatchers("/", "/login")
.anonymous()
.and()
.formLogin().loginPage("/login")
.defaultSuccessUrl("/buyer/list", true)
.and()
.logout()
.logoutSuccessUrl("/");