title: Vaadin combobox getValue() not getting what i want
body: <p>So i'm trying to get the selected value from a combobox  that holds register numbers for cars. So that the user can choose AAA-111, BBB-222 and so on. </p>
  
  <p>Now i would like to be able to get a hold of which value the the user has chosen in the combobox, but i can't seem to find a way to get it in the "AAA-111" form. Vaadin wants to give it as "entiteetit.Korjaustiedot@4024af35" when I use getValue(). And i have no use of that. </p>
  
  <p>I would like to be able to code it so its like: ok, "AAA-111" is chosen, now get AAA-111's info on the screen at the press of a button. Any ideas how to get the value from the combobox right?</p>
  
  <pre><code>ComboBox select = new ComboBox("Choose car");
  
  container = new BeanItemContainer&lt;Korjaustiedot&gt;(Korjaustiedot.class, korjaukset); // gets the data from my mysql database
  
      select.setContainerDataSource(container); //puts the data from the List &lt;Korjaustiedot&gt; into the container
  
      select.setItemCaptionPropertyId("registernumber"); //chooses the data from the column "registernumber"
  
      this.addComponent(select); 
  select.addValueChangeListener(event -&gt; // Java 8
      this.addComponent(new Label("Selected " +
          event.getProperty().getValue()))); 
  // this label only shows: Selected entiteetit.Korjaustiedot@4024af35
  </code></pre>