有关getRealPath()的问题

<%@ page contentType="text/html;charset=GBK" %>;
<%@ page session="true" import="java.util.*" %>;

<%
String strEnvs[][] =
 {
 {"CONTENT_LENGTH",String.valueOf(request.getContentLength())},
 {"CONTENT_TYPE",request.getContentType()},
 {"SERVER_PROTOCOL",request.getProtocol()},
 // {"SERVER_SOFTWARE",getServletContext().getServerInfo()},
{"SERVER_SOFTWARE",application.getServerInfo()},
{"SERVER_CLASSPATH",System.getProperty( "java.class.path" )},
{"REMOTE_ADDR",request.getRemoteAddr()},
 {"REMOTE_HOST",request.getRemoteHost()},
 {"REMOTE_USER",request.getRemoteUser()},
{"SERVER_NAME",request.getServerName()},
 {"SERVER_PORT",String.valueOf(request.getServerPort())},
 {"AUTH_TYPE",request.getAuthType()},
 {"REQUEST_METHOD",request.getMethod()},
 {"

ATH_INFO",request.getPathInfo()},
{"

ATH_TRANSLATED",request.getPathTranslated()},
         {"QUERY_STRING",request.getQueryString()},
         {"REQUEST_URI",request.getRequestURI()},
{"SCRIPT_NAME",request.getServletPath()},
      // {"DOCUMENT_ROOT",getServletContext().getRealPath("/"

}
{"DOCUMENT_ROOT",application.getRealPath("/"

}
 };
Enumeration enumNames;
String strName,strValue;
int i;
%>;

<html>;
<head>;

<title>;JSP例程 - 获取各种CGI环境变量</title>;
</head>;
<body>;;<CENTER>;JSP例程 - 获取各种CGI环境变量</CENTER>;
<table border=2 cellspacing=0 cellpadding=0 align=center>;
<tr>;
 <th>;;Name</th>;
 <th>;;Value</th>;
</tr>;
<%
enumNames = request.getHeaderNames();
while(enumNames.hasMoreElements()){
strName = (String)enumNames.nextElement();
strValue = request.getHeader(strName);
%>;
<tr>;
 <td>;&nbsp;;<%=strName%>;</td>;
 <td>;&nbsp;;<%=strValue%>;</td>;
</tr>;
<%
}
%>;
<tr>;
 <th>;;Name</th>;
 <th>;;Value</th>;
</tr>;
<%
for(i=0;i<strEnvs.length;i++){
%>;
<tr>;
 <td>;&nbsp;;<%=strEnvs[0]%>;</td>;
 <td>;&nbsp;;<%=strEnvs[1]%>;</td>;
</tr>;
<%
}
%>;
;;</table>;
</body>;
</html>;