<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%> 请求URI为：${pageContext.request.requestURI}
Content-Type响应头：${pageContext.response.contentType}
服务器信息为：${pageContext.servletContext.serverInfo}
Servlet注册名为：${pageContext.servletConfig.servletName}