jsp三大指令
一个jsp页面中可以有0-N个指令
1.page--->最复杂：<%@page language="" ...%>
*pageEncoding和contentType
pageEncoding:指定当前jsp页面的编码，只要不说谎，就不会有乱码！在服务器要把jsp编译成.java时需要使用pageEncoding
contentType：它表示添加一个响应头：Content-Type ，相当于response.setContentType()
*import:导包，可以出现多次
*errorPage和isErrorPage
errorPage：当前页面如果抛出异常，那么要转发到哪一个页面，由errorPage决定，状态码为200
isErrorPage：指定页面为处理错误页面！当该属性为true时，这个页面会设置状态码为500，而且这个页面可以使用9大内置对象中的exception
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8" errorPage="error/error.jsp"%> <% 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 'a.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"> --> </head> <body> <% int a=13/0; %> </body> </html> <%@ page language="java" import="java.util.*" pageEncoding="UTF-8" isErrorPage="true"%> <% 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 'error.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"> --> </head> <body> 哈哈，出错了！<br/> <% //<%=exception.getMessage()% > <br/> //<%exception.printStackTrace(response.getWriter()); % > //当然，一般不会直接将错误信息显示给用户，会变得人性化 %> </body> </html>