SecurityConfiguration that prevents authenticated user from accessing the /login page

SecurityConfiguration.java

package org.twinnation.stackoverflowspring.config;


import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
import org.springframework.security.config.annotation.method.configuration.EnableGlobalMethodSecurity;
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.context.SecurityContextHolder;
import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
import org.springframework.security.crypto.password.PasswordEncoder;
import org.springframework.security.web.authentication.ui.DefaultLoginPageGeneratingFilter;
import org.springframework.web.filter.GenericFilterBean;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;


@Configuration
@EnableWebSecurity
@EnableGlobalMethodSecurity(prePostEnabled = true)
public class SecurityConfiguration extends WebSecurityConfigurerAdapter {
	
	class LoginPageFilter extends GenericFilterBean {
		@Override
		public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
			if (SecurityContextHolder.getContext().getAuthentication() != null
				&& SecurityContextHolder.getContext().getAuthentication().isAuthenticated()
				&& ((HttpServletRequest)request).getRequestURI().equals("/login")) {
				System.out.println("user is authenticated but trying to access login page, redirecting to /");
				((HttpServletResponse)response).sendRedirect("/");
			}
			chain.doFilter(request, response);
		}
	}
	
	
	@Override
	protected void configure(HttpSecurity httpSecurity) throws Exception {
		httpSecurity.addFilterBefore(
			new LoginPageFilter(), DefaultLoginPageGeneratingFilter.class);
		
		httpSecurity.httpBasic()
			.and()
			.csrf().disable()
			.headers().frameOptions().sameOrigin()
			.and().formLogin().permitAll()
			.and().authorizeRequests().antMatchers("/login").not().authenticated()
			.and()
			.authorizeRequests()
				.anyRequest().authenticated();
	}
	
	
	@Bean
	public PasswordEncoder passwordEncoder() {
		return new BCryptPasswordEncoder();
	}
	
	
	@Override
	protected void configure(AuthenticationManagerBuilder auth) throws Exception {
		auth.inMemoryAuthentication()
			.withUser("root").password(passwordEncoder().encode("root")).roles("USER");
	}

}