Check out the Errai project which offers CDI integration with GWT.

I really recommend Vaadin. It's built on top of GWT and can be easily integrated into CDI.

Vaadin is great but I can't recommend to use it with CDI.  I've been playing with it a bit and it appears that you have to access all CDI components through your application class and it has to be done using the thread local pattern.  This doesn't make for a very modular design.

From what I can tell you can't simply sprinkle @Injects throughout Vaadin-based code.  I've tried @Injecting UI components instead of newing them but this is awkward at times and appears to run into problems when you get more than a few levels deep.

I definitely could be doing it wrong and I'd be pleased as punch to see an example where @Injection is being done throughout the application instead of just in the Application class.