title: Conditional dozer xml mapping
body: <p>In an object, i have two properties A and B. I want to map these properties based on condition to the target property T. I'm using xml based dozer mapping -</p>
  
  <pre><code>if(A != null)
    &lt;field&gt;
          &lt;a&gt;A&lt;/a&gt;
          &lt;b&gt;T&lt;/b&gt;
      &lt;/field&gt;
  else if (B != null)
     &lt;field&gt;
          &lt;a&gt;B&lt;/a&gt;
          &lt;b&gt;T&lt;/b&gt;
      &lt;/field&gt;
  </code></pre>
  
  <p>How to achieve this in xml ?</p>