Hi Wicket Team and Wicket Mailinglist!


As this is my first post on this list, I would like to introduce myself. My name is Sebastian and I am working on a university project, comparing Java web frameworks. As you might guess, my primary topic is the Wicket framework ;). I am not what one would call a programmer or coder, I guess. Rather someone familiar with the underling concepts, but sometimes a bit lots with the actual implementations of a certain language. So please excuse me, if my questions are stupid ;).


My problem at this moment is the following. I need to implement a feature in wicket that lets me upload images to a webpage and then use those images to be displayed on certain pages. It doesn’t really matter if the images are stored on the file system or in a database. I am not looking for a solution to an explicit problem but rather for a best practice that shows how the wicket framework supports such a feature.


I have tried to read up on anything I could find addressing such a feature. But everything I got so far is either way beyond my scope of understanding, not offering enough to archive the goal or just not working as I understand it should.


I have tried to read the example in the wiki (http://www.wicket-wiki.org.uk/wiki/index.php/UploadDownload), but I can not really follow it. Too many libraries used that are not included and overall to confusing for a non professional like myself.

I did understand the example for the upload in the wikiexamples though. No problems writing files to disk or even to database, following that example code.


My attempt to store images in the Database is looking something like this:


To write to the Database, I use this code sniped:


            public final void onSubmit()




                        // get the content of the upload field

                        final FileUpload upload_image = upload.getFileUpload();


                        // create a byte array of the uploaded item

                        byte[] bild = upload_image.getBytes();


                        if(upload_image != null)


                          *write byte[] to database*                  



                  catch (Exception e) { }



So far so good. Got my byte array stored. The source file is a jpeg image. I am not sure if I miss some kind cast here to let the system know what *sort* of byte array it should use.


When I try to retrieve the image from the database, I use the following code:


      public ResourceReference getImage()


            return new ResourceReference(some.class, "bild")


                  public BufferedDynamicImageResource newResource()




// get the byte[] from DB

                             byte[] bild = a.getBild();


// create a buffered image template

                             BufferedDynamicImageResource resource = new BufferedDynamicImageResource();

                             BufferedImage image = new BufferedImage(200, 200, BufferedImage.TYPE_INT_RGB);


// transform the byte[] back to an image (does it work that way? How does

// java know it was a jpeg before and not a gif for example?)

                             java.awt.Image i = Toolkit.getDefaultToolkit().createImage(bild);


                             // convert image to buffered image

                             image.getGraphics().drawImage(i, 0, 0, null);


                             Graphics g = image.getGraphics();

                             g.drawImage(i, 0, 0, null);



// return the image


                             return resource;


                        catch (Exception e) { }





This leads to a black box in the place my image is supposed to be. So I guess somewhere along the way I lose my image information. My best guess is, that the problem lies in the image conversion. Jpeg isn’t a java.awt.image, I suppose.


But still leaves the question, does wicket offer anything more to me to help me here? To make things (even) simpler for me?



The next attempt I took was storing images on the file system. This went pretty well, as it pretty much is covered by the upload example from the wicket examples. I was able to put the files in pretty much any directory I liked, following that code. The problems started once again, when I tried to retrieve and reuse the stored data. In the past I did a bit of PHP programming and was used to just store my things anywhere on the web server as a file and access them again via URL. This doesn’t really work for me in the java world (using jboss application server, ejb3, wicket), as the resources are stored in archives and not easily written to archives at runtime (at least to my current knowledge – please correct me if wicket offers a way to do such a thing).

I understand that wicket uses resource references to stream resources not in the actual “environment” of the core application. But I cannot seem to get that concept working correctly. I guess, my closest attempt to reference a resource outside an archive would be this one:



            java.io.File f = new java.io.File("d:/someimage.jpg");

            File ff = new File(f);


            FileResourceStream frs = new FileResourceStream(ff);


            ResourceStreamRequestTarget resource = new ResourceStreamRequestTarget(frs, frs.getContentType());


            String url = "">


            WebMarkupContainer bild = new WebMarkupContainer("bild");


            bild.add(new SimpleAttributeModifier("src", url));



which just leads to a runtime exception, I fail to understand. Something about not being able to stream the object, I think.


Once again, I am sure the problem is just based on my lack of java skills, rather then by anything wicket does, but never the less the question stands: Is there anything wicket can do for me in that situation to make my life easier and maybe even get the things done I want to do? What would be the best practice to archive the goal, using wicket? My current solution is a second webserver to which I upload the imagefiles and then refer them via URL in wicket, pretty much like I would, using PHP. But I guess that cannot be it, can it?


Thanks in advance for anyone taking the time to read this or even give me a few pointers. Sorry if my lack of java knowledge causes most of my problems. Please feel free to point me to any resource filling me in on what I am missing.



Sebastian Pflugbeil




















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