MyUI.scala

import java.io._
import java.util
import javax.servlet.annotation.WebServlet


import com.vaadin.annotations.{Push, Theme, VaadinServletConfiguration}
import com.vaadin.server.StreamResource.StreamSource
import com.vaadin.server.{FileDownloader, StreamResource, VaadinRequest, VaadinServlet}
import com.vaadin.ui.Button.ClickEvent
import com.vaadin.ui.{Label, UI, TabSheet, Upload}
import com.vaadin.ui.Upload.{Receiver, SucceededEvent, FinishedEvent, SucceededListener}

@Theme("mytheme") object MyUI {
  @WebServlet(urlPatterns = Array("/*"), name = "MyUIServlet", asyncSupported = true)
  @VaadinServletConfiguration(ui = classOf[MyUI], productionMode = false) class MyUIServlet extends VaadinServlet {
    override def servletInitialized() = {
    }
  }
}

@Push
@Theme("mytheme")
class MyUI extends UI {
  
  protected def init(vaadinRequest: VaadinRequest) {
    val t = new TabSheet
    val os = new ByteArrayOutputStream()
    val upload = new Upload
    upload.setReceiver((s: String, s1: String) => {
      os
    })
    upload.addFinishedListener((event: FinishedEvent) => {
    	//t.setSelectedTab(1)
    })
    upload.addSucceededListener((event: SucceededEvent) => {
      t.setSelectedTab(1)
    })
    
    
    t.addComponent(upload)
    t.addComponent(new Label("Second tab"))
    
    setContent(t)
  }
}