Problem with returning images from a servlet

[Pete Neu]

Hello,

I trying to return an image from a servlet as attachment. I know this question has been asked before but I couldn't find an answer on the forum.
The code to do this I copied from here: [ UD: removed link to copyrighted material ]

  
ByteArrayOutputStream out = new ByteArrayOutputStream();
response.addHeader("content-disposition",    "attachment;filename=Zeichnung.gif");
response.setContentType("image/gif");
String filePath = getServletContext().getRealPath("/images/mail.gif");
File f = new File(filePath);
FileInputStream fis = new FileInputStream(f);
byte[] buf = new byte[10 * 1024];  // 4K buffer
int bytesRead;
        while ((bytesRead = fis.read(buf)) != -1) {
 
            out.write(buf, 0, bytesRead);
        }
   

When I run the code I get no error. But when I open the attachmend dialogue I get the error that no file exists. The file is empty. I did some debugging but found no error. The picture has a size of 3k. The picture is in place under the path on the server.

Does anyone have an idea what's wrong?

cheers,
Pete
[ August 03, 2007: Message edited by: Ulf Dittmer ]

[Carl Trusiak]

Try flushing the output stream and closing it. It could be cached in the server and not sent.

        byte[] buf = new byte[10 * 1024];  // 4K buffer
        int bytesRead;
        while ((bytesRead = fis.read(buf)) != -1) {
            out.write(buf, 0, bytesRead);
        } 
        out.flush();
        out.close();

[ May 15, 2006: Message edited by: Carl Trusiak ]

[Ben Souther]

There are a couple things here..

I'm guessing the problem is that you're using a new instance of ByteArrayOutputStream. You might want to use a ServletOutputStream obtained with response.getOutputStream.

Also, if your file is kept within your web app, you might want to consider using context.getResourceAsStream instead of new File to read the image file.
The former will work regardless of how your application is deployed.
The getRealPath method will return null if your app is deployed from a packed war file.

Here is the code from one of my example apps:

 
package us.souther.simple;
                                                                                             
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.ServletException;
import java.io.*;
                                                                                             
public class StreamServlet  extends HttpServlet{
                                                                                             
                                                                                             
    public void doGet(HttpServletRequest  request,
                      HttpServletResponse response)
                             throws ServletException, IOException{
                                                                                             
        //
        // Parse URI to find the filename
        //
        String uri = request.getRequestURI();
        String[] tokens = uri.split("/");
        String filename = "";
        for(int i = 2; i < tokens.length; i++)
            filename += ("/" + tokens[i]);
                                                                                             
                                                                                             
        //
        // Set Content type
        //
        String contentType;
        if(filename.toLowerCase().endsWith(".png"))
            contentType = "image/png";
        else if(filename.toLowerCase().endsWith(".gif"))
            contentType = "image/gif";
        else
            contentType = "image/jpg";
                                                                                             
        //
        // Stream Image
        //
        BufferedInputStream in = null;
        try{
            in = new BufferedInputStream(
                getServletContext().
                    getResourceAsStream("WEB-INF" + filename));
                                                                                             
            response.setContentType(contentType);
            response.setHeader("Content-Disposition",
                               " inline; filename=" + filename);
                                                                                             
            ServletOutputStream out = response.getOutputStream();
                                                                                             
            byte[] buffer = new byte[4 * 1024];
                                                                                             
            int data;
            while((data = in.read(buffer)) != -1){
                out.write(buffer, 0, data);
            }
            out.flush();
        }catch(Exception e){
           return;
        }
    }
}