String path = request.getContextPath(); 
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; 
String remoteAddress=request.getRemoteAddr(); 
String servletPath=request.getServletPath(); 
String realPath=request.getRealPath("/"); 
String remoteUser=request.getRemoteUser(); 
String requestURI=request.getRequestURI(); 
out.println("path:"+path+"<br>"); 
out.println("basePath:"+basePath+"<br>"); 
out.println("remoteAddr:"+remoteAddress+"<br>"); 
out.println("servletPath:"+servletPath+"<br>"); 
out.println("realPath:"+realPath+"<br>"); 
out.println("remoteUser:"+remoteUser+"<br>"); 
out.println("requestURI:"+requestURI+"<br>"); 

path:/WebDemo 
basePath:http://localhost:8683/WebDemo/ 
remoteAddr:127.0.0.1 
servletPath:/index.jsp 
realPath:D:\apache-tomcat-6.0.13\webapps\WebDemo\ 
remoteUser:null 
requestURI:/WebDemo/index.jsp 

request.getRealPath("url");//虚拟目录映射为实际目录 
request.getRealPath("./");//网页所在的目录 
request.getRealPath("../");//网页所在目录的上一层目录 

request.getContextPath() => /uploading 
request.getServletPath() => /load.jsp 
request.getRequestURL() => http://localhost:8080/uploading/load.jsp 
request.getRealPath("/") =>  F:\learn\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\uploading\ 

ServletContext.getRealPath(java.lang.String) instead. 
request.getSession().getServletContext().getRealPath() 得到工程文件的实际物理路径,也就是绝对地址 

//Returns the part of this request's URL from the protocol name up to the query string in the first line of the HTTP request 
// eg./manage/editExam.domethod=goExamSet&type=U 
String url = request.getRequestURI();  
//The returned URL contains a protocol, server name, port number, and server path, but it does not include query string parameters 
//eg. http://127.0.0.1:8080/manage/editExam.domethod=goExamSet&type=U 
StringBuffer url_buffer = request.getRequestURL(); 

 String queryString = request.getQueryString(); 
ring fullPath = url + queryString;  // 或者是url_buffer.toString()+queryString;