Code 4 - Save File - UploadSave.jspx

JSP Tutorials - Herong's Tutorial Examples

∟Code 4 - Save File - UploadSave.jspx

This section provides a tutorial example of a JSP page, UploadSave.jspx, that reads the uploaded file and saves it on the Web server. The key logic is the request.getInputStream() call.

As you can see from the previous section, dumping uploaded files back to the browser is easy. But saving uploaded files on the server machine correctly is not so easy. I wrote the following JSP program, UploadSave.jsp, that scans the HTTP request body and saves uploaded files if there are any:

<?xml version="1.0"?>
<jsp:root xmlns:jsp="http://java.sun.com/JSP/Page" version="2.1">
<!-- UploadSave.jspx
 - Copyright (c) 2012, HerongYang.com, All Rights Reserved.
-->
<jsp:directive.page contentType="text/html"/>
<jsp:directive.page import="java.io.*"/>
<html><body>
<p>
<jsp:scriptlet><![CDATA[
   out.println("<pre>");
   ServletInputStream in = request.getInputStream();
   byte[] line = new byte[128];
   byte[] crlf = {(byte) 0x0D, (byte) 0x0A}; // \r\n
   String sLine = null;
   String enctype = null;
   String boundary = null;
   String status = null;
   String fName = null;
   FileOutputStream file = null;
   int i = in.readLine(line, 0, 128);
   boolean holdNewLine = false;
   while (i != -1) {
      boolean hasNewLine = i>=2 && line[i-1]==crlf[1] 
         && line[i-2]== crlf[0];
      if (hasNewLine) i = i-2;
      sLine = new String(line, 0, i);
      if (enctype==null) {
         // try to determine the encryption type
         if (i>3 && sLine.startsWith("--")) {
            enctype = "form-data";
            boundary = sLine;
            status = "boundary";
         } else {
            enctype = "x-www-form-urlencoded";
         }
         out.println(sLine);
      } else if (enctype.equals("x-www-form-urlencoded")) {
         out.println(sLine);
      } else if (enctype.equals("form-data")) {
         // Calculating the status of the current line
         if (status.equals("boundary")) {
            // Expecting the "Content-Disposition:" line
            status = "disposition";
         } else if (status.equals("disposition")) {
            // Expecting the "Content-Type:" line or a blank line
            if (sLine.startsWith("Content-Type:")) {
               status = "type";
            } else {
               status = "blank";
            }
         } else if (status.equals("type")) {
            // Expecting a blank line
            status = "blank";
         } else if (status.equals("blank")||status.equals("data")) {
            // Expecting the data or boundary
            if (sLine.startsWith(boundary)) {
               status = "boundary";
            } else {
               status = "data";
            }
         }
         // Now "status" is updated. Let's do the saving and echoing
         if (status.equals("disposition")) {
            // Getting the file name and open a file for saving
            int l = sLine.indexOf("filename=");
            if (l>=0) { 
               fName = sLine.substring(l+9);
               fName = fName.replaceAll("\"",""); 
               l = fName.lastIndexOf("\\");
               if (l>=0) fName = fName.substring(l+1);
               if (fName.length()>0) 
                  file = new FileOutputStream(
                     application.getRealPath("/upload/"+fName));
            } 
         } else if (status.equals("boundary")) {
            fName = null;
            if (file!=null) {
               file.close();
               file = null;
            }
         }
         if (status.equals("data")) {
            if (file!=null) {
               if (holdNewLine) file.write(crlf);
               file.write(line,0,i);
               holdNewLine = hasNewLine;
            } else {
               out.println(status+": "+fName+": "+sLine);
               holdNewLine = false;
            }
         } else {
            out.println(status+": "+fName+": "+sLine);
            holdNewLine = false;
         }
      }
      i = in.readLine(line, 0, 128);
   }
   out.println("</pre>");
]]></jsp:scriptlet>
</p>
</body></html>
</jsp:root>

Note that I am planning to save uploaded files in the .\upload directory under the Tomcat application document directory: \local\apache-tomcat-7.0.32\webapps\ROOT. So I have to create the .\upload directory first.

More notes are provided in later sections.

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