title: Using map of maps as Maven plugin parameters
body: <p>Is it possible to use a map of maps as a Maven plugin parameter?, e.g.</p>
  
  <pre class="lang-java prettyprint-override"><code>@Parameter
  private Map&lt;String, Map&lt;String, String&gt;&gt; converters;
  </code></pre>
  
  <p>and then to use it like </p>
  
  <pre><code>&lt;converters&gt;
    &lt;json&gt;
       &lt;indent&gt;true&lt;/indent&gt;
       &lt;strict&gt;true&lt;/strict&gt;
    &lt;/json&gt;
    &lt;yaml&gt;
        &lt;stripComments&gt;false&lt;/stripComments&gt;
    &lt;/yaml&gt;
  &lt;converters&gt;
  </code></pre>
  
  <p>If I use it like this, <code>converters</code> only contain the keys <code>json</code> and <code>yaml</code> with null as values.</p>
  
  <p>I know it is possible to have complex objects as values, but is it also somehow possible to use maps for variable element values like in this example?</p>