Accessing File System from JSP Pages

JSP Tutorials - Herong's Tutorial Examples

∟Accessing File System from JSP Pages

This section provides a tutorial example on how to access the file system from JSP pages using 3 different reference points: Current Directory, Physical Root Directory, and Virtual Root Directory.

The next area I want to test is about how to generate non-HTML response body and set response header lines to match the body. But before writing any testing JSP pages, I need to figure out how to read files on the Tomcat server within JSP pages in order to build non-HTML response body.

Reading files on the Tomcat server requires a good understanding of the file system from the JSP page point of view. With the default configuration, the Tomcat 7 server gives you 3 path name reference points into the file system:

Current Directory - Reference point for a physical relative path name, which can be used directly in java.io.* classes. For example, (File = new File(".\test\hello.pdf");).
Physical Root Directory - Reference point for a physical absolute path name, which can also be used directly in java.io.* classes. For example, (File = new File("\herong\test\hello.pdf");).
Virtual Root Directory - Reference point for a virtual absolute path name, which can be used indirectly in java.io.* classes through the application.getRealPath() method. For example, (File = new File(application.getRealPath("/data/hello.pdf"));).

To find out where are those reference points located in the file system, I wrote this JSP tutorial example, CheckPathName.jspx:

<?xml version="1.0"?>
<jsp:root xmlns:jsp="http://java.sun.com/JSP/Page" version="2.1">
<!-- CheckPathName.jspx
 - Copyright (c) 2012, HerongYang.com, All Rights Reserved.
-->
 <jsp:directive.page session="false" import="java.io.*" />
 <jsp:scriptlet><![CDATA[
   String text = "<html><body><pre>";

   try {
      File d = new File(".");
      text += "\n Current Directory: "+d.getAbsolutePath();
      text += "\n Can Execute: "+d.canExecute();
      text += "\n Can Read: "+d.canRead();
      text += "\n Can Write: "+d.canWrite();
      text += "\n";
 
      File p = new File("\\");
      text += "\n Physical Root Directory: "+p.getAbsolutePath();
      text += "\n Can Execute: "+p.canExecute();
      text += "\n Can Read: "+p.canRead();
      text += "\n Can Write: "+p.canWrite();
      text += "\n";

      File v = new File(application.getRealPath("/"));
      text += "\n Virtual Root Directory: "+v.getAbsolutePath();
      text += "\n Can Execute: "+v.canExecute();
      text += "\n Can Read: "+v.canRead();
      text += "\n Can Write: "+v.canWrite();
      text += "\n";
   } catch (Exception e) {
      text += "\n Exception: "+e.toString();
   }

   text += "</pre></body></html>";
   response.setContentType("text/html;charset=UTF-8");
   response.setContentLength(text.length());
   out.print(text);
 ]]></jsp:scriptlet>
</jsp:root>

Deploy this JSP page to the default application on the Tomcat 7 server, and visit it with a Web browser, you should see the following output:

 Current Directory: C:\Users\herong\.
 Can Execute: true
 Can Read: true
 Can Write: true

 Physical Root Directory: C:\
 Can Execute: true
 Can Read: true
 Can Write: true

 Virtual Root Directory: C:\local\apache-tomcat-7.0.32\webapps\ROOT
 Can Execute: true
 Can Read: true
 Can Write: true

Based on the output, we can conclude that:

"Current Directory" of a Tomcat 7 server on a Windows 7 system is the login user home directory.
"Physical Root Directory" of a Tomcat 7 server is the root directory of the physical disk drive.
"Virtual Root Directory" of a Tomcat 7 server application is the home directory of the application on the Tomcat 7 server. "Virtual Root Directory" is the recommended reference point when specifying path names to access the file system in JSP pages.

Note that on older versions, for example Tomcat 5, "Current Directory" is actually having the same location as "Virtual Root Directory". So if you have old JSP pages that use "Current Directory", you might have problems upgrading to Tomcat 7.

Last update: 2012.

Table of Contents

About This Book

JSP (JavaServer Pages) Overview

Tomcat 7 Installation on Windows Systems

JSP Scripting Elements

Java Servlet Introduction

JSP Implicit Objects

Syntax of JSP Pages and JSP Documents

JSP Application Session

Managing Cookies in JSP Pages

JavaBean Objects and "useBean" Action Elements