title: Spring Web Flow exception handling
body: <p>How to prevent exception, 
  if <code>requestParameters.sortBy</code> is passed as string (<code>java.lang.NumberFormatException</code>) or is missing (<code>java.lang.NullPointerException</code>)?</p>
  
  <pre><code>&lt;view-state id="journeySearch" model="journeyForm"&gt;
  
       ...
  
      &lt;transition on="sort"&gt;
          &lt;set name="journeyCriteria.sortBy" value="requestParameters.sortBy" type="int" /&gt;
          &lt;evaluate expression="bookingService.searchJourneys(journeyCriteria)" result="viewScope.journeys" /&gt; 
      &lt;/transition&gt;
  &lt;/view-state&gt;
  </code></pre>