how to download file from server through servlet

[subodh varshney]

i want to download a file from server through servlet using inputstream.
if any one have any code plz help me.

[David O'Meara]

What are your requirements? You just want them to make a request to a servlet and the servlet sends them the file?

There was a similar discussion here, but the solution I quite liked was to use the RequestDiospatcher. You may need to set the filename and content type first.

Otherwise you can read from a FileInputStream and write to the OutputStream, but you would still need the filename and content type to be set.

[David O'Meara]

It is better to continue conversations here rather than emailing people. You were lucky, I usually don't check that address for days at a time...

--------------------------------------
From email:
i have download this code but i don't know how to use this.

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.MalformedURLException;
import java.net.SocketException;
import java.net.URL;
 
import javax.servlet.ServletException;
import javax.servlet.UnavailableException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
public class TestServ extends HttpServlet
{
    Exception exception;
 
    public void doGet(HttpServletRequest req, HttpServletResponse res)
        throws ServletException, IOException, UnavailableException
    {
 
        int bytesRead = 0;
        int count = 0;
        byte[] buff = new byte[1];
 
        OutputStream out = res.getOutputStream();
 
        //---------------------------------------------------------------
        // Set the output data's mime type
        //---------------------------------------------------------------
 
        res.setContentType("application/pdf");//application/pdf" ); // MIME
                                              // type for pdf doc
 
        //---------------------------------------------------------------
        // create an input stream from fileURL
        //---------------------------------------------------------------
 
        String fileURL = "http://localhost:7001/soap.pdf";
 
        //------------------------------------------------------------
        // Content-disposition header - don't open in browser and
        // set the "Save As..." filename.
        // *There is reportedly a bug in IE4.0 which ignores this...
        //------------------------------------------------------------
 
        //-----------------------------------------------------------------
        // PROXY_HOST and PROXY_PORT should be your proxy host and port
        // that will let you go through the firewall without authentication.
        // Otherwise set the system properties and use
        // URLConnection.getInputStream().
        //-----------------------------------------------------------------
        BufferedInputStream bis = null;
        BufferedOutputStream bos = null;
        boolean download = false;
 
        res.setHeader("Content-disposition", "attachment; filename=xml.pdf;");
 
        try
        {
 
            URL url = new URL(fileURL);
            bis = new BufferedInputStream(url.openStream());
            bos = new BufferedOutputStream(out);
 
            while (-1 != (bytesRead = bis.read(buff, 0, buff.length)))
            {
                try
                {
                    bos.write(bytesRead);
                    bos.flush();
                }//end of try for while loop
                catch (SocketException e)
                {
                    setError(e);
                    break;
                }
                catch (Exception e)
                {
                    System.out.println("Exception in while of TestServlet is " + e.getMessage());
                    if (e != null)
                    {
                        System.out.println("File not downloaded properly");
 
                        setError(e);
                        break;
 
                    }//if ends
 
                }//end of catch for while loop
 
            }//while ends
 
            Exception eError = getError();
 
            if (eError != null)
            {
 
                System.out.println("\n\n\n\nFile Not DownLoaded properly\n\n\n\n");
            }
            else if (bytesRead == -1)
            {
                System.out.println("\n\n\n\ndownload successful\n\n\n\n");
 
            }
            else
            {
                System.out.println("\n\n\n\ndownload not successful\n\n\n\n");
            }
 
        }
        catch (MalformedURLException e)
        {
            System.out.println("Exception inside TestServlet is " + e.getMessage());
 
        }
        catch (IOException e)
        {
            System.out.println("IOException inside TestServlet is " + e.getMessage());
        }
 
        finally
        {
            try
            {
                if (bis != null)
                    bis.close();
                if (bos != null)
                    bos.close();
            }
            catch (Exception e)
            {
                System.out.println("here =" + e);
            }
        }
 
    }//doPost ends
 
    public void setError(Exception e)
    {
        exception = e;
        System.out.println("\n\n\nException occurred is " + e + "\n\n\n");
 
    }
 
    public Exception getError()
    {
        return exception;
    }
}//class ends

I have formatted the code and cleaned it a little. There are some key problems with this code, I suggest you don't use it.

The bits you are interested in look like this:

    public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException
    {
        int bytesRead = 0;
        byte[] buff = new byte[2048];
 
        OutputStream out = response.getOutputStream();
 
        response.setContentType("application/pdf");
        BufferedInputStream bis = null;
        BufferedOutputStream bos = null;
 
        response.setHeader("Content-disposition", "attachment; filename=xml.pdf;");
 
        try
        {
            bis = new BufferedInputStream(new FileInputStream("file name here!"));
            bos = new BufferedOutputStream(out);
 
            while (-1 != (bytesRead = bis.read(buff, 0, buff.length)))
            {
                bos.write(bytesRead);
                bos.flush();
            }
        }
        finally
        {
            if (bis != null)
                bis.close();
            if (bos != null)
                bos.close();
        }
    }

[David O'Meara]

Essentially you set the content type and 'filename' on the response. The lines for these should be obvious. You use a FileInputStream of some other type of stream to suck in a file, then pump it down the OutputStream. When you run out of data, stop.

Actually there is a bug in the bos.write(bytesRead) line, that's not right at all. Icky code.

[David O'Meara]

If the file is available on the context, you could also try:

public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException
{
    response.setContentType("application/pdf");
    response.setHeader("Content-disposition", "attachment; filename=xml.pdf;");
    request.getRequestDispatcher("/xml.pdf").include(request, response);
}

I haven't tried this, but it appeals to me.