礼悟：
好好学习合思考，尊师重道存感恩。叶见寻根三返一，江河湖海同一体。
虚怀若谷良心主，愿行无悔给最苦。读书锻炼强身心，诚劝且行且珍惜。
javaEE：7
javaSE：1.8
JSTL：1.2.2
server：tomcat 8.5
browser：Chrome/Firefox
os：windows7 x64
ide：MyEclipse 2017
好习惯：在开发中，page指令放第一行。
page 可以有多个
<%@ page language="java" import="java.util.*"%><%@ page pageEncoding="UTF-8"%><%String path = request.getContextPath();String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort()+ path + "/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><base href="<%=basePath%>"><title>My JSP ‘index.jsp‘ starting page</title><meta http-equiv="pragma" content="no-cache"><meta http-equiv="cache-control" content="no-cache"><meta http-equiv="expires" content="0"><meta http-equiv="keywords" content="keyword1,keyword2,keyword3"><meta http-equiv="description" content="This is my page"><!--<link rel="stylesheet" type="text/css" href="styles.css">--><script type="text/javascript">function _change() {var img = document.getElementById("pictureImg");// new Date().getTime() 因为缓存而生img.setAttribute("src", "/Day12/VerifyCodeServlet?time=" + new Date().getTime());}</script></head><body><img id="pictureImg" src="/Day12/VerifyCodeServlet" /><a href="javascript:_change()">换一换</a></body></html>
不写第一行也行
<%String path = request.getContextPath();String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort()+ path + "/";%><%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><base href="<%=basePath%>"><title>My JSP ‘index.jsp‘ starting page</title><meta http-equiv="pragma" content="no-cache"><meta http-equiv="cache-control" content="no-cache"><meta http-equiv="expires" content="0"><meta http-equiv="keywords" content="keyword1,keyword2,keyword3"><meta http-equiv="description" content="This is my page"><!--<link rel="stylesheet" type="text/css" href="styles.css">--><script type="text/javascript">function _change() {var img = document.getElementById("pictureImg");// new Date().getTime() 因为缓存而生img.setAttribute("src", "/Day12/VerifyCodeServlet?time=" + new Date().getTime());}</script></head><body><img id="pictureImg" src="/Day12/VerifyCodeServlet" /><a href="javascript:_change()">换一换</a></body></html>学习资源：itcast和itheima视频库。如果您有公开的资源，可以分享给我的话，用您的资源学习也可以。
博文是观看视频后，融入思考写成的。博文好，是老师讲得好。博文坏，是 给最苦 没认真。
JSP基础 指令page 可以放在第一行，也可以放在其他行，可以有多个
原文地址：http://www.cnblogs.com/jizuiku/p/7992071.html