Request获取url信息的各种方法比较

1、request.getRequestURL()

返回的是完整的url，包括Http协议，端口号，servlet名字和映射路径，但它不包含请求参数。
2、request.getRequestURI()

得到的是request URL的部分值，并且web容器没有decode过的

3、request.getContextPath() 
返回 the context of the request.

4、request.getServletPath() 
返回调用servlet的部分url.

5、request.getQueryString() 
返回url路径后面的查询字符串

示例：

当前url：http://localhost:8080/CarsiLogCenter_new/idpstat.jsp?action=idp.sptopn

request.getRequestURL() http://localhost:8080/CarsiLogCenter_new/idpstat.jsp
request.getRequestURI() /CarsiLogCenter_new/idpstat.jsp
request.getContextPath()/CarsiLogCenter_new
request.getServletPath() /idpstat.jsp

request.getQueryString()action=idp.sptopn

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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
要想得到完整请求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();
String fullPath = url + queryString;   // 或者是url_buffer.toString()+queryString;