package com.smartmap.sample.ch1.controller.view;import org.springframework.stereotype.Controller;import org.springframework.ui.Model;import org.springframework.util.StringUtils;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestParam;@Controller@RequestMapping("/system")public class MainViewController {    @RequestMapping("")    public String index(@RequestParam(required = false, name = "sessionId") String sessionId, Model model) {        if (sessionId == null || sessionId.equals("")) {            return "redirect:/system/login.html";            // return "forward:/system/login.html";        } else {            String osName = System.getProperty("os.name");            model.addAttribute("name", "hello world");            model.addAttribute("host", osName);            return "index";        }    }    @RequestMapping("/login.html")    public String login(@RequestParam(required = false, name = "username") String username,            @RequestParam(required = false, name = "password") String password, Model model) {        if (StringUtils.isEmpty(username) || StringUtils.isEmpty(password)) {            return "login.html";        } else {            return "redirect:/system?sessionId=12345";        }    }}