Uploading files with RAP 1.4

One of the new things in RAP 1.4 is the FileUpload widget in RWT, that replaces the old Upload widget from the sandbox. And there’s some more new upload stuff in the RAP Incubator. Here’s how to use the new features to upload files with RAP 1.4.

The FileUpload is a new widget that wraps the HTML file selection tag. It looks like a button, and when it’s pressed, a native file dialog opens up that lets users select a file from their local file system. On file selection, a SelectionEvent will be fired. You can then programmatically upload the selected file to an http server using FileUpload.submit( URL ).

In order to receive and store the uploaded files on the server, you also need a server-side component. We created such an upload server component in the RAP Incubator. It’s called FileUploadHandler and it uses the Apache fileupload component internally. It’s included in the bundle org.eclipse.rap.rwt.supplemental.fileupload. This handler accepts file uploads to a certain URL (FileUploadHandler.getUploadUrl()) and delegates the data to a FileUploadReceiver. You can either use the provided DiskFileUploadReceiver or create your own receiver to do whatever you like with the uploaded data: put it into a database, or simple analyze the data and discard it.

Sounds complicated? Well, there’s a much easier way to upload files with RAP 1.4! We’ve encapsulated the entire upload process in an implementation of the SWT FileDialog, which is also available in the incubator.

To make it easy to use, we now provide an update site for the Incubator. To use the FileDialog in your application, all you have to do is to:

1. include the bundles from the RAP Incubator repository https://download.eclipse.org/rt/rap/1.4/incubator/ in your RAP 1.4 target platform, and
2. add a bundle dependency to org.eclipse.rap.rwt.supplemental.filedialog to your project (yes, you have to use Require-Bundle here because this bundle contributes a class to the org.eclipse.swt.widgets package, effectively creating a split-package).

That’s all. Now you can use the FileDialog just like in SWT:

  FileDialog fileDialog = new FileDialog( shell, SWT.TITLE | SWT.MULTI );
  fileDialog.setText( "Upload Files" );?
  fileDialog.setAutoUpload( true ); // This API will change, see below!
  fileDialog.open();
  String[] fileNames = fileDialog.getFileNames();

After uploading, the dialog closes and the variable fileNames contains the absolute file names of the uploaded files on the server’s file system. There’s an auto-upload feature that is really nice (I think it should be the default) - with autoUpload on, the upload starts immediately after file selection. A user can still press Cancel to prevent the application from using the uploaded files.

Note: Please note that this stuff is in the incubator and not part of the 1.4 release. The API and implementation may (and will) have to change and mature over time. However, if you use the latest version from 1.4/incubator site, you’ll always get a file dialog that will work with RAP 1.4. The server-side upload receiver and the required Apache bundles are also included.

We hope you enjoy these new features. Please try them out, tell us what you think, open bugs for the new stuff, and help us improving them.

Kudos to our new RAP committers Austin Riddle and Cole Markham who created this great new feature!

Update: I mistakenly left out the “.rwt.” from the bundle namespace in the original post, the bundle names are fixed now in the text.

Update: The 1.4 incubator repository has been updated with a newer version of the file dialog that is compatible with RAP 1.4. This update fixes the problem with missing file names mentioned in the comments.