Upload multiple files at once using GWT

I'm desperately trying to enable the multiple-property to users of my webside. User should be able to upload a bunch of PDF-files to my server without choosing each file separately. I'm using gwt-upload for my uploads. Sadly the

MultiUploader

does not actually lets the user select several files at once, but you have to click the "Browse"-Button for every file again and select in in the browser.

I researched and realised that I need to have something like this

<input name='uploads[]' type="file" multiple>

Setting the "multiple"-property at the input created from gwt-upload does the trick so far that the opening file-dialog lets me select several files, but then the upload does not start / work anymore.

I could not find any example using a multi-file-input with gwt. It would be perfect if there is a way to do this with gwt-upload because I do not really want to implement the whole upload logic by myself again!

Thanks a lot!

The solution is pretty simple. gwt-upload has a class Uploader which is able to do multiple uploads. The servlet code suggested in the wiki of gwt-upload is already capable of handling multiple uploads.

I had to change somethings in the Uploader class (source is fully available, so I just copied it and replaced the parts I needed). To access filenames and filesizes of the selected files I created a simple native method:

private static native String getFilesSelected() /*-{
    var count = $wnd.$('input:file')[0].files.length;

    var out = "";

    for (i = 0; i < count; i++) {
        var file = $wnd.$('input:file')[0].files[i];
        out += file.name + ';' + file.size + ";";
    }
    return out;
}-*/;

whichs return value I split by ; to get the needed results.

And you need to replace the uploaders FileInput (setFileInput()) with a custom one, which sets the multiple property to the input. I use a wrapper class like this:

public class MyFileInput implements IFileInput {

    private final FileUpload fu;

    public MyFileInput() {
        fu = new FileUpload();
        DOM.setElementProperty(fu.getElement(), "multiple", "multiple");    
    }
}

you obviously need to implement the other methods of IFileInput, I linked them all through to fu. Two had no equivalent method, but I dont use them, so no problem here ...