System.out.println( " 根目录所对应的绝对路径: "   +  request.getServletPath()  +   "" ); 
String strPathFile 
=  request.getSession().getServletContext().getRealPath(request.getRequestURI()); 
System.out.println(
" 文件的绝对路径: "   +  strPathFile  +   "" ); 
String strDirPath 
=   new  File(request.getSession().getServletContext().getRealPath(request.getRequestURI())).getParent(); 
System.out.println(
" 目录的绝对路径: "   +  strDirPath  +   "" ); 
    this.getServlet().getServletContext().getRealPath("/");//在struts的action中取得当前系统的根目录

 举例:http://localhost:7001/myservlet/somepath/test?someparam=somevalue
request.getPathInfo():返回
/ somepath / test
request.getRequestURL():返回http:
// localhost:7001/myservlet/somepath/test
request.getRequestURI():返回 / myservlet / somepath / test
request.getServletPath():返回
/ myservlet
request.getQueryString():返回someparam
= somevalue
    request.getContextPath();  返回项目名/myservlet