SecurityDemoController.java

package com.raj.controller;

import org.springframework.security.authentication.AnonymousAuthenticationToken;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.web.bind.annotation.GetMapping;

@org.springframework.stereotype.Controller
public class Controller {

    @GetMapping("/home")
    public String showHome() {
        return "home";
    }

    @GetMapping("/hello")
    public  String showGreetings() {
        return "hello";
    }

    @GetMapping("/login")
    public String showLoginPage() {

        Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
        if (authentication == null || authentication instanceof AnonymousAuthenticationToken) {
            return "login";
        }
        return "redirect:/home";
    }

}