title: Add Json Creator to 3rd party library with final class that use a builder
body: <p>I need use Jackson to deserialize a final class without a default constructor of a third-party library. Instances of the class are constructed via a builder.</p>
  <p>I may use <code>@JsonCreator</code> because is an external library, but I can't use <code>MixIn</code> because is a final class...</p>
  <p>I have tried adding a new <code>JsonDeserializer</code>, which instantiates the object using the builder but Jackson does not populate any of the object's fields after creation.</p>
  <p>Is there any way to add an &quot;external&quot; <code>JsonCreator</code> or create a <code>JsonDeserializer</code> which, after instantiating the object, uses a default mechanism to populate the object's fields?</p>
  <p>This is the deserializer:</p>
  <pre class="lang-kotlin prettyprint-override"><code>class BlockDeserializer : JsonDeserializer&lt;Block&gt;() {      
      override fun deserialize(parser: JsonParser, context: DeserializationContext): Block {         
         return Block.builder().build()
     }  
  } 
  </code></pre>
  <p>I need add &quot;something&quot; to populate the block before return it.</p>