jsp Request獲取url信息的各類方法比較

從Request對象中能夠獲取各類路徑信息，如下例子：
假設請求的頁面是index.jsp,項目是WebDemo，則在index.jsp中獲取有關request對象的各類路徑信息以下
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>");
結果：
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
從上不難看出request各個對應方法所表明的含義

從request獲取各類路徑總結：
request.getRealPath("url");//虛擬目錄映射爲實際目錄
request.getRealPath("./");//網頁所在的目錄
request.getRealPath("../");//網頁所在目錄的上一層目錄
假定你的web application(web應用)名稱爲news，你的瀏覽器中輸入請求路徑：http://localhost:8080/uploading/load.jsp
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\
如今request.getRealPath("/") 這個方法已經不推薦使用了
能夠使用
ServletContext.getRealPath(java.lang.String)  instead.
request.getSession().getServletContext().getRealPath() 獲得工程文件的實際物理路徑,也就是絕對地址

      //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();
  HttpServletRequest 的這兩種方法都只能獲得不包含參數的請求url，區別以下：
1 前者返回相對路徑，後者返回完整路徑
2 前者返回string ，後者返回stringbuffer
獲得完整請求url能夠經過以下方法，getQueryString()獲得的是url後面的參數串，和前者相加就是帶參數的請求路徑了
  String queryString = request.getQueryString();
ring fullPath = url + queryString;   // 或者是url_buffer.toString()+queryString;