noteworthy/2.3/_news-M2.html

<div>

  <h3>Heads up: Webkit bug, affects Chrome, Safari and Opera</h3>

  <p>
    Recently, a <a href="https://bugs.webkit.org/show_bug.cgi?id=125070">bug</a> has been introduced
    in WebKit that leads to RAP UIs becoming partly invisible when a Canvas widget is included.
    This problem also affects earlier versions of RAP running in recent WebKit-based browsers.
    A workaround is outlined in <?=bug(428717)?>, but didn't make it into this milestone.
    We're confident to include it in M3. For older versions of RAP, please visit the
    <a href="https://wiki.eclipse.org/RAP/FAQ#Widgets_disappearing_in_Google_Chrome.2C_Safari_or_Opera">FAQ</a>
    for workarounds that you can apply yourself.
  </p>

  <h3>Drag&amp;Drop Support for Client Files</h3>

  <p>
    You can now allow users to upload files from their desktop by dropping them onto a widget.
    To do so, you use the SWT Drag&amp;Drop API with the transfer type
    <code>ClientFileTransfer</code>.
    The following example shows how to enable a Label to accept files:
  </p>

<pre lang="java">
Label dropLabel = new Label( parent, SWT.BORDER );
dropLabel.setText( &quot;Drop files here&quot; );
DropTarget dropTarget = new DropTarget( dropLabel, DND.DROP_MOVE );
dropTarget.setTransfer( new Transfer[]{ ClientFileTransfer.getInstance() } );
dropTarget.addDropListener( new DropTargetAdapter() {
  @Override
  public void drop( DropTargetEvent event ) {
    filesDropped( (ClientFile[])event.data );
  }
} );
</pre>

  <p>
    The <code>event.data</code> field will contain an array of <code>ClientFile</code>s, that
    provide information on the dropped files.
    It's an array because the user can also select and drag multiple files.
    To actually upload the dropped files, the new client service <code>ClientFileUploader</code>
    can be used:
  </p>

<pre>
ClientFileUploader uploader = RWT.getClient().getService( ClientFileUploader.class );
uploader.submit( uploadUrl, clientFiles );
</pre>

  <p>
    Finally, you have to accept and store the files on the server.
    The fileupload component in the <a href="http://eclipse.org/rap/incubator/">RAP Incubator</a>
    can be used to handle uploads in RAP easily.
    The <code>FileDialog</code>, also in the RAP Incubator, now also accepts dropped files.
  </p>

  <h3>New API for Singletons</h3>

  <p>
    We already provide the class <em>SingletonUtil</em> to facilitate the conversion of classic
    singletons to UISession-scoped singletons for use in RAP's multi-user environment.
    This class has a new method named <em>getUniqueInstance</em> that accepts a UISession instance
    as a parameter. You can obtain a unique instance of a given class for the current UISession like so:
  </p>

<pre lang="java">
public static MySingleton getInstance() {
  UISession uiSession = RWT.getUISession();
  return SingletonUtil.getUniqueInstance( MySingleton.class, uiSession );
}
</pre>

  <p>
    In this case, the method is equivalent to the existing method <code>getSessionInstance()</code>.
    However, with the additional parameter, it allows you to obtain the singleton instance
    for a given UISession <em>even from another thread</em> without having to wrap your code
    in a runnable and pass it to <code>uiSession.exec()</code>.
    To prepare your singleton for access from background threads, you may consider adding a
    parameter to the getInstance method as shown below.
    This pattern also allows for better unit tests.
  </p>

<pre lang="java">
private static MySingleton getInstance( UISession uiSession ) {
  return SingletonUtil.getUniqueInstance( MySingleton.class, uiSession );
}
</pre>

  <p>
    The old method <code>getSessionInstance()</code> still exists and delegates to the new one,
    so you should be able to adjust your code using an “Inline Method” refactoring.
  </p>

  <h3>Support for Application Singletons</h3>

  <p>
    Similar to UISession singletons, you can now also create singletons with application scope.
    Whenever you run multiple RAP applications in a single VM, there may be classes in a shared
    bundle that should have exactly one instance per application.
  </p>

<pre lang="java">
ApplicationContext context = RWT.getApplicationContext();
SingletonUtil.getUniqueInstance( MySingleton.class, applicationContext );
</pre>

</div>