<a href ="test.jsp?p=fuck">跳转到test2</a>

test2.jsp=======================

<%@ page language="java" import="java.util.*" pageEncoding="gb2312"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

out.println("basePath:"+basePath);
out.println("<br/>");
out.println("getContextPath:"+request.getContextPath());
out.println("<br/>");
out.println("getServletPath:"+request.getServletPath());
out.println("<br/>");
out.println("getRequestURI:"+request.getRequestURI());
out.println("<br/>");
out.println("getRequestURL:"+request.getRequestURL());
out.println("<br/>");
out.println("getRealPath:"+request.getRealPath("/"));
out.println("<br/>");
out.println("getServletContext().getRealPath:"+getServletContext().getRealPath("/"));
out.println("<br/>");
out.println("getQueryString:"+request.getQueryString());

%>

请求路径:
http://localhost:8080/test/test.jsp?p=fuck

显示结果：

basePath:http://localhost:8080/test/

getContextPath:/test 
getServletPath:/test.jsp 
getRequestURI:/test/test.jsp 
getRequestURL:http://localhost:8080/test/test.jsp 
getRealPath:D:\Tomcat 6.0\webapps\test\ 
getServletContext().getRealPath:D:\Tomcat 6.0\webapps\test\ 
getQueryString:p=fuck

在一些应用中，未登录用户请求了必须登录的资源时，提示用户登录，此时要记住用户访问的当前页面的URL，当他登录成功后根据记住的URL跳回用户最后访问的页面：

String lastAccessUrl = request.getRequestURL() + "?" + request.getQueryString();

from : http://www.cnblogs.com/JemBai/archive/2010/11/10/1873764.html