Create and show thumbnail (byte[]) in JSF

Question

I\'m uploading image to server and when image is uploaded it should show me a thumb of uploaded image. Thumbnail is not saved on hard disc I use InputStream and OutputStream

Answer 1

The images counts each as a separate request. You cannot process both the HTML response (of JSF) and the image in a single request/response cycle. You need to store the image/thumb somewhere in a datastore which lives longer than a request, e.g. the server's local disk file system (temp folder? webcontent folder?), or a database (temp table?), or in the session.

First, replace

by

so that it get generated as

(the src should namely point to a valid URL)

Then, create a HttpServlet which is mapped on an url-pattern of /thumbs/* and implement doGet() roughly like follows:

Long thumbId = Long.valueOf(request.getPathInfo().substring(1)); // 123
byte[] thumb = getItFromDiskOrDatabaseOrSessionByThumbId(thumbId);
String filename = getOriginalFilenameOfUploadedImageOrInventOne();

response.setContentType(getServletContext().getMimeType(filename));
response.setContentLength(thumb.length);
response.setHeader("Content-Disposition", "inline; filename=\"" + filename + "\"");

BufferedInputStream input = null;
BufferedOutputStream output = null;

try {
    input = new BufferedInputStream(new ByteArrayInputStream(thumb));
    output = new BufferedOutputStream(response.getOutputStream());
    byte[] buffer = new byte[8192];
    int length;
    while ((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 it. More servlet hints can be found in this article.