public class LoginInterceptor implements HandlerInterceptor {

  @Override
  public void afterCompletion(HttpServletRequest request,
                HttpServletResponse response, Object obj, Exception err)
      throws Exception {
  }

  @Override
  public void postHandle(HttpServletRequest request, HttpServletResponse response,
              Object obj, ModelAndView mav) throws Exception {

  }

  @Override
  public boolean preHandle(HttpServletRequest request, HttpServletResponse response,
               Object obj) throws Exception {
    //获取session里的登录状态值
    String str = (String) request.getSession().getAttribute("isLogin");
    //如果登录状态不为空则返回true，返回true则会执行相应controller的方法
    if(str!=null){
      return true;
    }
    //如果登录状态为空则重定向到登录页面，并返回false，不执行原来controller的方法
    response.sendRedirect("/backend/loginPage");
    return false;
  }
}

@Controller
@RequestMapping("/backend")
public class BackendController {

  @RequestMapping(value = "/loginPage", method = {RequestMethod.GET})
  public String loginPage(HttpServletRequest request,String account, String password){
    return "login";
  }

  @RequestMapping(value = "/login", method = {RequestMethod.POST})
  public String login(HttpServletRequest request,RedirectAttributes model, String account, String password){
    //验证账号密码，如果符合则改变session里的状态，并重定向到主页
    if ("jack".equals(account)&&"jack2017".equals(password)){
      request.getSession().setAttribute("isLogin","yes");
      return "redirect:IndexPage";
    }else {
      //密码错误则重定向回登录页，并返回错误，因为是重定向所要要用到RedirectAttributes
      model.addFlashAttribute("error","密码错误");
      return "redirect:loginPage";
    }
  }
  //登出，移除登录状态并重定向的登录页
  @RequestMapping(value = "/loginOut", method = {RequestMethod.GET})
  public String loginOut(HttpServletRequest request) {
    request.getSession().removeAttribute("isLogin");
    return "redirect:loginPage";
  }
  @RequestMapping(value = "/IndexPage", method = {RequestMethod.GET})
  public String IndexPage(HttpServletRequest request){
    return "Index";
  }

}

  <!--省略其他基本配置-->

  <!-- 配置拦截器 -->
  <mvc:interceptors>
    <!-- 配置登陆拦截器 -->
    <mvc:interceptor>
      <!--拦截后台页面的请求-->
      <mvc:mapping path="/backend/**"/>
      <!--不拦截登录页和登录的请求-->
      <mvc:exclude-mapping path="/backend/loginPage"/>
      <mvc:exclude-mapping path="/backend/login"/>
      <bean class="com.ima.Interceptor.LoginInterceptor"></bean>
    </mvc:interceptor>
  </mvc:interceptors>

public class LoginInterceptor implements HandlerInterceptor {

  @Override
  public void afterCompletion(HttpServletRequest request,
                HttpServletResponse response, Object obj, Exception err)
      throws Exception {
  }

  @Override
  public void postHandle(HttpServletRequest request, HttpServletResponse response,
              Object obj, ModelAndView mav) throws Exception {

  }

  @Override
  public boolean preHandle(HttpServletRequest request, HttpServletResponse response,
               Object obj) throws Exception {
//    获取request的cookie
    Cookie[] cookies = request.getCookies();
    if (null==cookies) {
      System.out.println("没有cookie==============");
    } else {
//      遍历cookie如果找到登录状态则返回true执行原来controller的方法
      for(Cookie cookie : cookies){
        if(cookie.getName().equals("isLogin")){
          return true;
        }
      }
    }
//    没有找到登录状态则重定向到登录页，返回false，不执行原来controller的方法
    response.sendRedirect("/backend/loginPage");
    return false;
  }
}

@Controller
@RequestMapping("/backend")
public class BackendController {

  @RequestMapping(value = "/loginPage", method = {RequestMethod.GET})
  public String loginPage(HttpServletRequest request, String account, String password) {
    return "login";
  }

  @RequestMapping(value = "/login", method = {RequestMethod.POST})
  public String login(HttpServletRequest request, HttpServletResponse response, RedirectAttributes model, String account, String password) {
    if ("edehou".equals(account) && "aidou2017".equals(password)) {
      Cookie cookie = new Cookie("isLogin", "yes");
      cookie.setMaxAge(30 * 60);// 设置为30min
      cookie.setPath("/");
      response.addCookie(cookie);
      return "redirect:IndexPage";
    } else {
      model.addFlashAttribute("error", "密码错误");
      return "redirect:loginPage";
    }
  }

  @RequestMapping(value = "/logOut", method = {RequestMethod.GET})
  public String loginOut(HttpServletRequest request, HttpServletResponse response) {
    Cookie[] cookies = request.getCookies();
    for (Cookie cookie : cookies) {
      if (cookie.getName().equals("isLogin")) {
        cookie.setValue(null);
        cookie.setMaxAge(0);// 立即销毁cookie
        cookie.setPath("/");
        response.addCookie(cookie);
        break;
      }
    }
    return "redirect:loginPage";
  }

  @RequestMapping(value = "/IndexPage", method = {RequestMethod.GET})
  public String IndexPage(HttpServletRequest request) {
    return "Index";
  }

}