参考url:http://203.75.156.21:91/udap/
获取协议名: http
request.getScheme();
端口: 8080
request.getServerPort();
服务器: localhost
request.getServerName();
项目名: udap
request.getContextPath();
ServletPath: servlet/DemoServlet
request.getServletPath();
整个请求路径:” http://localhost:8080/kefuwebsocket/servlet/DemoServlet
request.getRequestURL()
项目的路径:”D:\Tomcat7.0\webapps\kefuwebsocket”
request.getSession().getServletContext().getRealPath(“”)