記憶登錄跳轉可以大大方便用戶，使用getHeader("Referer");方式簡單，不過不能處理post的參數，本來這些代碼都是用在struts,webwork里的，為了容易看明白改寫成jsp方式的。
<!--此頁面的內容受保護，必須登錄才能訪問-->
<%@ page contentType="text/html; charset=GBK" %>
<jsp:useBean id="rect" class="com.util.myRedirect" scope="page"/>
<%
String url = "";
if(session.getAttribute("userid")==null)//如果用戶沒有登錄
{
???url =rect.dealurl(request);
//記憶進入此頁面的地址和請求參數，dealurl將實際url進行處理,因為有&字符
???response.sendRedirect("weblogin.jsp?url="+url) ;
//重定向到登錄頁面，記憶的url作為參數一起傳入
}else{
????out.println("你已經登錄，可以下載了");
} %>
weblogin.jsp
<%@ page contentType="text/html; charset=GBK" %>
<jsp:useBean id="myRedirect" class="com.util.myRedirect" scope="page"/>
<%
String url = request.getParameter("url");
String userid =request.getParameter("userid");
String password =request.getParameter("password");
if(userid!=null)?//如果是登錄提交執行下面代碼
{
?if(登錄成功)
??{
???session.setAttribute("userid",userid);?
???out.println("<script>alert('登錄成功，謝謝光臨');self.location.href='"+myRedirect.geturl(url)+"';</script>");
//轉向到首次請求的url，.geturl(url)是把轉化過的地址轉化回來變成真實url.
??}else{
???out.println("<script>alert('用戶名或密碼錯誤');history.back();</script>");
??}
}else{//如果不是登錄提交顯示現面登錄界面
%>
<table width="311" height="162" border="0" align="center" cellpadding="0" cellspacing="0">
? <tr>
?????
??? <td width="311" height="162" align="center"> 您還沒有登錄，請先登錄<br>
??????? <table width="155" border="0" cellpadding="0" cellspacing="5" class="font12">
??<form? name="loginfrm" action="weblogin.jsp" method="post"? id="loginfrm" onSubmit="return checkfrm();">
????????? <tr>
??????????? <td width="41" height="33" valign="bottom">帳 號：</td>
??????????? <td width="99" valign="bottom"><input name="userid" type="text" class="textstyle" id="userid" size="12" style="height:20"></td>
????????? </tr>
????????? <tr>
??????????? <td>密 碼：</td>
??????????? <td><input name="password" type="password" class="textstyle" id="password" size="12" style="height:20;width:94"></td>
????????? </tr>
????????? <tr align="center" valign="bottom">
??????????? <td height="21" colspan="2"> <input type="submit" name="Submit" value="登錄">
????????????? <a href="reg.jsp" target="_blank">沒有注冊</a> </td>
????????? </tr>
????????? <tr align="center">
??????????? <td colspan="2" class="font14"> <strong>
<a href="#" onclick="MM_openBrWindow('requestpwd.jsp','pwd','width=300,height=200');return false;">找回密碼</a></strong></td>
????????? </tr>
??? <input name="url" type="hidden" value="<%=url%>"><!--這里要有個hidden來保存一下，不然提交就沒了 -->
????
??? </form>
??????? </table>????
??? </td>
? </tr>
</table>
<%
}
%>
---------------------------------------------------------------
myRedirect.java
package com.util;
import javax.servlet.http.HttpServletRequest;
import java.util.Enumeration;
public class myRedirect??? //對url的轉換類
{
?public static String dealurl(HttpServletRequest request)
?{
??String url = "";
??url = request.getRequestURL()+"?";
??url +=param(request);
??if(url.indexOf("&")>-1)
???url=url.replaceAll("&","@#@");//實際上就是把有&的字符轉化成了@#@
??return url;
?}
?public static String geturl(String url)//這個是還原方法
?{
??if(url.indexOf("@#@")>-1)
???url=url.replaceAll("@#@","&");
??return url;?????
?}
?public static String param(HttpServletRequest request)
?{
??String url = "";
??Enumeration param = request.getParameterNames();//得到所有參數名
??while(param.hasMoreElements())
??{
???String pname = param.nextElement().toString();
???url += pname+"="+request.getParameter(pname)+"&";
??}
??if(url.endsWith("&"))
??{
???url = url.substring(0,url.lastIndexOf("&"));
??}
??return url;
?}
}