Web应用中request获取path，URI，URL

Web应用中有各种获取path或URI，URL的方法，假设网页访问地址:

http://localhost:8080/tradeload/TestServlet

Web应用context: /tradeload

各路径鉴定如下：

1. request.getContextPath()= /tradeload
2. request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort()= http://localhost:8080
3. request.getRequestURL() = http://localhost:8080/tradeload/TestServlet
4. request.getRequestURI() = /tradeload/TestServlet
5. request.getPathInfo() = null
6. request.getServletPath() = /TestServlet
7. getServletContext().getRealPath('/') = C:\server\glassfish\domains\domain1\applications\j2ee-modules\tradeload\

其中的servletpath就是web.xml中配置的url-pattern。

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假定你的web application 名称为news,你在浏览器中输入请求路径：
http://localhost:8080/news/main/list.jsp 
则执行下面向行代码后打印出如下结果：

1、System.out.println(request.getContextPath());

打印结果：/news

2、System.out.println(request.getServletPath());

打印结果：/main/list.jsp

3、System.out.println(request.getRequestURI());

打印结果：/news/main/list.jsp

4、System.out.println(request.getRealPath("/"));

打印结果：F:\Tomcat 6.0\webapps\news\test

String path = request.getContextPath();

String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

out.println("basePath:"+basePath);

out.println("<br/>");

out.println("getContextPath:"+request.getContextPath());

out.println("<br/>");

out.println("getServletPath:"+request.getServletPath());

out.println("<br/>");

out.println("getRequestURI:"+request.getRequestURI());

out.println("<br/>");

out.println("getRequestURL:"+request.getRequestURL());

out.println("<br/>");

out.println("getRealPath:"+request.getRealPath("/"));

out.println("<br/>");

out.println("getServletContext().getRealPath:"+getServletContext().getRealPath("/"));

out.println("<br/>");

out.println("getQueryString:"+request.getQueryString());

显示结果：

basePath:http://localhost:8080/test/

getContextPath:/test
getServletPath:/test.jsp
getRequestURI:/test/test.jsp
getRequestURL:http://localhost:8080/test/test.jsp
getRealPath:D:\Tomcat 6.0\webapps\test\
getServletContext().getRealPath:D:\Tomcat 6.0\webapps\test\
getQueryString:p=fuck

在一些应用中，未登录用户请求了必须登录的资源时，提示用户登录，此时要记住用户访问的当前页面的URL，当他登录成功后根据记住的URL跳回用户最后访问的页面：

String lastAccessUrl = request.getRequestURL() + "?" + request.getQueryString();