下面是一个request内置对象与forward指令的实例，只要是为了说明request在请求中获取请求参数，操作request的范围属性，以及当使用forward转发用户请求的时候，客户端的请求参数和请求属性不会丢失。。
<%@ page language="java" import="java.util.*" pageEncoding="GBK"%>
<%
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>取钱的表单页</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>
This is my JSP page. <br>
<!-- 取钱的表单 -->
<form method= "post" action="first.jsp">
取钱： <input type="text" name="balance">
<input type="submit" value="提交">
</form>
</body>
</html>
<%@ page language="java" import="java.util.*" pageEncoding="GBK"%>
<%@ page import="java.util.*" %>
<%
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 ‘first.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>
//
<%
String str = request.getParameter("balance");
double qian = Double.parseDouble(str);
if(qian<500)
{
out.println("账户余额减少："+qian);
}else
{
List<String> info = new ArrayList<String>();
info.add("AAAAAAAAA");
info.add("BBBBBBBBB");
info.add("CCCCCCCCC");
request.setAttribute("info", info);
%>
<!-- 实现转发 -->
<jsp:forward page="second.jsp"></jsp:forward>
<%
}
%>
</body>
</html>
<%@ page language="java" import="java.util.*" pageEncoding="GBK"%>
<%@ page import="java.util.*" %>
<%
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 ‘second.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>
<%
String str = request.getParameter("balance");
double qian = Double.parseDouble(str);
List<String> info =(List<String>)request.getAttribute("info");
for(String trm:info)
{
out.println(trm+"<br>");
}
out.println("取钱"+qian+"快");
%>
</body>
</html>
表明，使用forward用户请求时，请求参数与request范围的属性都不会丢失，即forward的动作还是原来的请求，并未向服务器再次发请求。
时间： 2024-12-23 02:12:20