title: Default value from DTD in xStream
body: <p>Geven XML file</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;!DOCTYPE ExternalRequestContext [
  &lt;!ELEMENT ExternalRequestContext EMPTY&gt;
  &lt;!ATTLIST ExternalRequestContext
   requestType CDATA #REQUIRED
   deepEnrichment (true | false) "false"
   channelMandatory (true | false) "true"&gt;
  ]
  &gt;
  
  &lt;ExternalRequestContext requestType="News" deepEnrichment="false" /&gt;
  </code></pre>
  
  <p>And xStream code</p>
  
  <pre><code>@XStreamAlias("ExternalRequestContext")
  class ERC {
   private String requestType;
   private boolean deepEnrichment;
   private boolean channelMandatory;
  }
  ...
  XStream x = new XStream();
  x.processAnnotations(ERC.class);
  ERC erc = (ERC)x.fromXML(new FileReader("C:/Projects/Forwarder/Test.xml"));
  x.toXML(erc, System.out);
  </code></pre>
  
  <p>My browser renders it as following:</p>
  
  <pre><code>&lt;ExternalRequestContext requestType="News" deepEnrichment="false" channelMandatory="true" /&gt;
  </code></pre>
  
  <p>Note that <strong>channelMandatory="true"</strong> (browser processed the DTD instruction)</p>
  
  <p>while xStream produces</p>
  
  <pre><code>&lt;ExternalRequestContext&gt;
    &lt;deepEnrichment&gt;false&lt;/deepEnrichment&gt;
    &lt;channelMandatory&gt;false&lt;/channelMandatory&gt;
  &lt;/ExternalRequestContext&gt;
  </code></pre>
  
  <p>Here <strong>channelMandatory="false"</strong> (xStream ignored the "channelMandatory (true | false) "true"" DTD instruction)</p>
  
  <p>What do I miss? How to "tell" xStream to process DTD instructions?
  And how do I enable DTD validation in xStream?</p>