jsp Request获取url信息的各种方法比较

     从Request对象中可以获取各种路径信息，以下例子：
     假设请求的页面是index.jsp,项目是WebDemo，则在index.jsp中获取有关request对象的各种路径信息如下
     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>");
     结果：
     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
     从上不难看出request各个对应方法所代表的含义  

     从request获取各种路径总结：
     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
     假定你的web application(web应用)名称为news，你的浏览器中输入请求路径：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\
     现在request.getRealPath("/") 这个方法已经不推荐使用了
     可以使用
     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();
  HttpServletRequest 的这两种方法都只能得到不包含参数的请求url，区别如下：
1 前者返回相对路径，后者返回完整路径
2 前者返回string ，后者返回stringbuffer
得到完整请求url可以通过如下方法，getQueryString()得到的是url后面的参数串，和前者相加就是带参数的请求路径了
  String queryString = request.getQueryString();
ring fullPath = url + queryString;   // 或者是url_buffer.toString()+queryString;