我想实现要用户名和密码才能下载一个文件！--我是新手

Question

点链接进入下载页面传参数？file＝test.rar
判断是否登陆用户
是跳转到下载页面传参数？file＝test.rar
否跳转到登陆页面下载页面:
<%@ page language="java" import="com.jspsmart.upload.*"%>
<jsp:useBean id="mySmartUpload" scope="page" class="com.jspsmart.upload.SmartUpload" />
<%    // Initialization 
mySmartUpload.initialize(pageContext);   
// Download file  //
//mySmartUpload.downloadFile("/upload/sample.zip");   
// With a physical path 
 mySmartUpload.downloadFile("g:\\user\\temp\\test.rar") ;
// With options 
// mySmartUpload.downloadFile("/upload/sample.zip","application/x-zip-compressed","downloaded.zip") 
%>

Answer 1

<%
response.setHeader("Cache-Control","no-cache"); //HTTP 1.1
response.setHeader("Pragma","no-cache"); //HTTP 1.0
response.setDateHeader ("Expires", -1);
//prevents caching at the proxy server
response.setDateHeader("max-age", 0);
%>这段代码是做什么的？