How to make file download in JSP ?

Question

Friends,
i am using following code :
// LISTING FILES IN DIR
        out.println("<br>");
        File dir = new File(dirName);
        String[] children = dir.list();
             if (children == null)
        // Either dir does not exist or is not a directory
             else
                %>
                <table border="1" cellpadding="0" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" width="68%" id="AutoNumber1">
                <tr>
                    <td width="50%" align="center"><font face="Verdana">File</font></td>
                    <td width="50%" align="center"><font face="Verdana">Action</font></td>
                      </tr>   
                    <%
                    for (int i=0; i<children.length; i++)
                    // Get filename of file or directory
                    String filename = children;
//out.println(filename);
%>
<tr>
<td width="50%">
<p align="center"><font face="Verdana"><%=filename %></font></td>
<td width="50%">
<p align="center"><font face="Verdana"><a href="<%= children[i %">">View</a></font></td>
</tr>
<%
out.println("<br>");
%>
SInce i am not able to download file from link.
link shows path correct but why its not working ??
HELP ME.
*i don't want to show real path( physical location of file) on file donwload link.*
Example :
*it will not allow to show like following :*
*C:\project\webUpload\build\web\fuploads\file2.jpg*
*it may allow like :*
*\webUpload\fuploads\file2.jpg*
Thanks</a>

Answer 1

My friend you are getting it all wrong here...
Here we would be taking help of a dedicated servlet to locate and download a file(which would be the output the respective concent of depeding of the fineName or fileId you send in).
Please find some time and try to consider the below case...
Say i have a Servlet which takes a Request of detailed filePath and would give output as file itself....
and you prompt you give a link to that servlet from you JSP to download that file...
Checkout the below Code snippets to get some idea
DownloadPrompting.JSP:
==================
<a href="FileServlet?fileName=C:\fileuploaded\image1.jpg" title="C:\fileuploaded\image1.jpg">Click Here to download Image1 JPEG File</a>
<c:forEach var="fileName" items="${sessionScope.fileNames}">
   <a href="FileServlet?fileName=<c:uri value="${fileName}"/>" title="<c:out value="${fileName}"/>">Click Here to download</a>
</c:forEach>
-------------------------------------------------------------------------FileServlet.java
===========
package com;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.URLConnection
public class FileServlet extends HttpServlet{
  private void processAction(HttpServletRequest request,HttpServletResponse response) throws Exception{
       // getting fileName which user is requesting for
       String fileName = request.getParameter("fileName").replace('\\','/');
       boolean exists = new File(fileName).exists();
       // Checking whether the file Exists or not      
       if(exists){
        FileInputStream input = null;
        BufferedOutputStream output = null; 
        int contentLength = 0;
        try{
            // Getting the Mime-Type
            String contentType = URLConnection.guessContentTypeFromName(fileName); 
            if(contentType == null)        
               contentType = "application/octet-stream";
            input = new FileInputStream(fileName);
            contentLength = input.available();
            // Enables us to specify of what kind of content we are trying to download.
            response.setContentType(contentType);
            // Specifes How much amountof data we straming & trying to download
            response.setContentLength(contentLength);
            // Adding Content Disposition header so that it cud enable us to get OPEN/SAVE  after clicking on the link 
            response.setHeader("Content-Disposition","attachment;filename="+fileName+"\");
            // Initializing File Streaming Response via a Servlet
            output = new BufferedOutputStream(response.getOutputStream());
            // Placing each byte on to the stream after reading it from the file
            while ( contentLength-- > 0 ) {
               output.write(input.read());
             // Flushing the stream.         
             output.flush();
          }catch(IOException e) {
                 System.err.println("Exception Occured:"+e.getMessage());
             System.err.println("Exception Localized Message:"+e.getLocalizedMessage());
          } finally {
               // Closing the INPUT stream 
               if (input != null) {
                   try {
                      input.close();
                  } catch (IOException ie) {
                      System.err.println("Exception Occured:"+e.getMessage());
                         System.err.println("Exception Localized Message:"+e.getLocalizedMessage());                      
               // Closing the OUTPUT stream 
               if (output != null) {
                   try {
                      output.close();
                  } catch (IOException ie) {
                      System.err.println("Exception Occured:"+e.getMessage());
                         System.err.println("Exception Localized Message:"+e.getLocalizedMessage());                      
       }else{
         response.sendRedirect("/errorPage.html");
  public void doPost(HttpServletRequest request,HttpServletResponse response) throws Exception{       
        processAction(request,response); 
  public void doGet(HttpServletRequest request,HttpServletResponse response) throws Exception{
        processAction(request,response); 
}And if you are thinking of hiding filepath & all...
Here is a hint for you...
Try to maintain a properties file which has a key value pairs of that something like.
112345678=C:\\uploadfile\\image1.jpg
122142637=C:\\uploadfile\\image2.jpg
or create a Database table which which an autogenerated primany key with some Id and holds the complete filePath.
and in this case you would access the file something like the one below from your jsp
<a href="FileServlet?fileId=112345678" title="112345678">Click Here to download Image1 JPEG File</a>
<c:forEach var="fileId" items="${sessionScope.fileNames}">
   <a href="FileServlet?fileId=<c:uri value="${fileId}"/>" title="<c:out value="${fileId}"/>">Click Here to download</a>
</c:forEach>
-------------------------------------------------------------------------and in the fileServlet you might have to change the below part to
// getting fileName which user is requesting for
       String fileName = request.getParameter("fileName").replace('\\','/');to something like
// getting fileName which user is requesting for
       String fileId = request.getParameter("fileId");
   /*Querying the database or reading the Properties file to findout the correspoding filePath associated with the fileId something like*/
    String fileName = ResourceDelegate.getInstance().getFile("fileId").replace('\\','/');
NOTE:* The idea is similar to what my fellow poster is trying to explain you in all his posts.
Hope that might help :)
REGARDS,
RaHuL