SpringMVC拦截器实现监听session是否过期详解

<mvc:interceptors>
  <mvc:interceptor>
    <mvc:mapping path="/**"/>
    <mvc:exclude-mapping path="/user/login"/>  <!-- 不拦截登录请求 -->
    <mvc:exclude-mapping path="/user/logout"/>  <!-- 不拦截注销请求 -->
    <mvc:exclude-mapping path="*.jsp"/>
    <mvc:exclude-mapping path="*.html"/>
    <mvc:exclude-mapping path="*.js"/>
    <mvc:exclude-mapping path="*.css"/>
    <bean class="org.huaxin.interceptor.accessinterceptor"></bean>
  </mvc:interceptor>
</mvc:interceptors>

public boolean prehandle(httpservletrequest request, httpservletresponse response,
      object obj) throws exception {
    system.out.println("[accessinterceptor]:prehandle执行");
    httpsession session = request.getsession();
    servletcontext application = session.getservletcontext();
    if(application.getattribute(session.getid()) == null){  //未登录
      printwriter out = response.getwriter();
      stringbuffer sb = new stringbuffer("<script type=\"text/javascript\" charset=\"utf-8\">");
      sb.append("alert(\"你的账号被挤掉，或者没有登录，或者页面已经过期，请重新登录\")");
      sb.append("window.location.href='/user/logout';");
      sb.append("</script>");
      out.print(sb.tostring());
      out.close();
      return false;
    }else{  //已经登录
      return true;
    }
  }