title: How to use modelMapper to convert nested classes
body: <p>I have a simple class that I want to map to a DTO class using modelMapper.</p>
  
  <pre><code>class Source {
  
      private String name;
      private String address;
      List&lt;Thing&gt; things;
  
      // getters and setters follows
      }
  
      class Thing {
  
      private String thingCode;
      private String thingDescription;
  
      // getters and setters
  }
  </code></pre>
  
  <p>and I want to convert these to a sourceDTO that contains a list of ThingDTOs, for example</p>
  
  <pre><code>class sourceDTO {
  
      private String name;
      private String address;
      List&lt;ThingDTO&gt; things;
  
      // getters and setters.
      }
  
       class ThingDTO {
  
      private String thingCode;
      private String thingDescription;
  
      // getters and setters
  }
  </code></pre>
  
  <p>If I drop my list of Things and list of ThingsDTO then modelmapper is a delight to use, </p>
  
  <pre><code> modelMapper.map(source, SourceDTO.class);
  </code></pre>
  
  <p>But I can't work out how to get the mapper to convert the List of Things to List of ThingDTOs. From the documentation, I think I need to create a mapper class that extends PropertyMap but I can't work out how to configure it.</p>
  
  <p>Any pointers to the relevant documentation would be welcome</p>