javax.imageio.ImageIO Problem creating ImageInputStream

Question

I have a Servlet in Tomcat 5.5 that reads local images sitting on a folder. The image is then sent back to an Applet.

I'm getting this "javax.imageio.IIOException: Can't create an ImageInputStream!" error and not sure whats causing it.

Has anyone had this problem before? Could this be a Thread issue in the ImageIO? I can't reproduce this issue since it occurs about 3 times for every 1000 requests.

EDIT: This is the Servlet code that reads the image. I just use the ImageIO.read(File) in its static form inside the Servlet's doPost method the same way below:

    doPost(req,resp){
       ...
        BufferedImage image = ImageIO.read(imageFile);
       ...
    }

Here is the source code for javax.imageio.ImageIO.read(File):

    public static BufferedImage read(File input) throws IOException {
    if (input == null) {
        throw new IllegalArgumentException("input == null!");
    }
    if (!input.canRead()) {
        throw new IIOException("Can't read input file!");
    }

    ImageInputStream stream = createImageInputStream(input);
    if (stream == null) {
        throw new IIOException("Can't create an ImageInputStream!");
    }
    BufferedImage bi = read(stream);
    if (bi == null) {
        stream.close();
    }
    return bi;
    }

Answer 1

If the sole functional requirement is to read images from local disk and return it unmodified to the HTTP response using a servlet, then you do not need the ImageIO at all. It only adds unnecessary overhead and other problems like you're having now.

Get rid of the ImageIO stuff and just stream the raw image straight from disk to HTTP response, along a set of proper response headers. For example,

String name = request.getParameter("name");
File file = new File("/path/to/images", name);

response.setContentType(getServletContext().getMimeType(file.getName()));
response.setHeader("Content-Length", String.valueOf(file.length()));
response.setHeader("Content-Disposition", "inline; filename=\"" + file.getName() + "\"");

InputStream input = null;
OutputStream output = null;

try {
    input = new BufferedInputStream(new FileInputStream(file));
    output = new BufferedOutputStream(response.getOutputStream());
    byte[] buffer = new byte[8192];

    for (int length; (length = input.read(buffer)) > 0;) {
        output.write(buffer, 0, length);
    }
} finally {
    if (output != null) try { output.close(); } catch (IOException logOrIgnore) {}
    if (input != null) try { input.close(); } catch (IOException logOrIgnore) {}
}

That's all. You only need ImageIO whenever you would like to manipulate the image in server's memory before returning it, e.g. resizing, transforming or something.

Another, more robust, example of such a servlet can be found here and a more advanced one here.