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The moose likes Servlets and the fly likes loading image Big Moose Saloon
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loading image

Bob Moranski
Ranch Hand

Joined: Nov 22, 2000
Posts: 177
import java.awt.*;
import javax.servlet.*;
import javax.servlet.http.*;
import Acme.JPM.Encoders.GifEncoder;
public class Confidentializer extends HttpServlet {
Frame frame = null;
Graphics g = null;
public void init(ServletConfig config) throws ServletException {
// Construct a reusable unshown frame
frame = new Frame();
public void doGet(HttpServletRequest req,
HttpServletResponse res)
throws ServletException, IOException {
ServletOutputStream out = res.getOutputStream();
try {
// Get the image location from the path info
String source = req.getPathTranslated();
if (source == null) {
throw new ServletException("Extra path information " +
"must point to an image");
// Load the image (from bytes to an Image object)
MediaTracker mt = new MediaTracker(frame);
// frame acts as an ImageObserver
Image image = Toolkit.getDefaultToolkit().getImage(source);
mt.addImage(image, 0);
try {
catch (InterruptedException e) {
getServletContext().log(e, "Interrupted while loading image");
throw new ServletException(e.getMessage());
// Construct a matching-size off screen graphics context
int w = image.getWidth(frame);
int h = image.getHeight(frame);
Image offscreen = frame.createImage(w, h);
g = offscreen.getGraphics();
// Draw the image to the off screen graphics context
g.drawImage(image, 0, 0, frame);
// Encode the off screen graphics into a GIF and send it to
// the client
GifEncoder encoder = new GifEncoder(offscreen, out);
finally {
// Clean up resources
if (g != null) g.dispose();
public void destroy() {
// Clean up resources
if (frame != null) frame.removeNotify();
Hi, I tried to invoke the above servlet with a gif file but the browser shows blank. Can someone please help me explain what the problem might be?
William Brogden
Author and all-around good cowpoke

Joined: Mar 22, 2000
Posts: 13028
Try setting the content length - some browsers are very picky about this. You will have to output to a ByteArrayOutputStream first in order to get that length. That will give you an additional chance to check that everything is working since you can also write that byte array to a file.

author of:
Bob Moranski
Ranch Hand

Joined: Nov 22, 2000
Posts: 177
Thank you so much Bill!
I agree. Here's the link:
subject: loading image
jQuery in Action, 3rd edition