title: DropDownChoice wicket get value
body: <p>so I have my DropDownChoice in Wicket:</p>
  
  <pre><code>final DropDownChoice drop_down_status = new DropDownChoice&lt;String&gt;("status", new PropertyModel&lt;String&gt;(this,"selected_status"), STATUS_LIST);
  
       form.add(drop_down_status);
  </code></pre>
  
  <p>How to get the selected value? I have to get it after another button is pressed and prepare sql statement from it.</p>
  
  <p>drop_down_status.getRawInput()  and drop_down_status.getInput() return null ( at least in my case).</p>
  
  <p>cheers</p>