/**
 * 登錄攔截器
 */
public class LoginInterceptor implements HandlerInterceptor {
  /**
   * 在控制層方法請(qǐng)求之前調(diào)用，返回一個(gè)boolean類型值
   * 如果返回的true則放行，如果返回false，則不繼續(xù)往后執(zhí)行
   * @param request
   * @param response
   * @param handler
   * @return
   * @throws Exception
   */
  @Override
  public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    String requestURI = request.getRequestURI();
    System.out.println("攔截到請(qǐng)求："+requestURI);
    Admin admin = (Admin) request.getSession().getAttribute("admin");
    //如果admin為空，說(shuō)明沒(méi)有登錄
    if (admin==null){
      response.sendRedirect(request.getContextPath()+"/login.jsp");
      return false;//不繼續(xù)往后執(zhí)行
    }
    return true;
  }

  /**
   * 在控制層方法執(zhí)行返回之后執(zhí)行，通?？梢宰鲆恍┤值臄?shù)據(jù)返回等
   * @param request
   * @param response
   * @param handler
   * @param modelAndView 控制層方法返回的結(jié)果
   * @throws Exception
   */
  @Override
  public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
    System.out.println("進(jìn)入攔截器postHandle方法");
    //ajax請(qǐng)求時(shí)，modelView為null
    if (modelAndView!=null){
    System.out.println("獲取到控制層方法返回結(jié)果："+modelAndView.getModelMap()
            +"view："+modelAndView.getViewName());
    }
  }

  /**
   * 視圖解析之后執(zhí)行，通常用來(lái)做一些清理工作
   * @param request
   * @param response
   * @param handler
   * @param ex
   * @throws Exception
   */
  @Override
  public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    System.out.println("進(jìn)入afterCompletion方法");
  }
}

<!--  配置springmvc攔截器-->
  <mvc:interceptors>
    <mvc:interceptor>
      <!--      定義需要攔截的請(qǐng)求；/**:表示以/開(kāi)頭的任意控制層請(qǐng)求;  /*:只能攔截一個(gè)/的請(qǐng)求-->
      <mvc:mapping path="/**"/>
      <!--      定義不攔截的請(qǐng)求-->
      <mvc:exclude-mapping path="/admin/login"/>
      <!--      配置攔截類-->
      <bean id="loginInterceptor" class="aop.LoginInterceptor"></bean>
    </mvc:interceptor>
  </mvc:interceptors>

//在方法參數(shù)中定義HttpSession，HttpServletRequest，HttpServletResponse等對(duì)象，springmvc會(huì)自動(dòng)注入該對(duì)象
  @RequestMapping("/login")
  public String login(String account, String password, HttpSession session){
    //根據(jù)用戶名查詢是否存在該用戶
    Admin admin = adminService.selectByAccount(account);
    if (admin!=null && admin.getPassword().equals(password)){
      //將用戶信息放入session
      session.setAttribute("admin",admin);
      return "redirect:list";
    }
    return "/login.jsp";//以/開(kāi)頭為絕對(duì)路徑,/對(duì)應(yīng)webapp目錄
  }