title: deserialize json using jackson with dynamic field name
body: <p>I'm trying to deserialize json using jackson, the problem is that field names are not always the same, for instance </p>
  
  <p>One call will give me </p>
  
  <pre><code>{
    id: "blabla"
    aFieldname : { an object if type A} 
  }
  
  Another call will give me 
  
  {
    id: "blabla"
    anotherName : { the same kind of object } 
  }
  </code></pre>
  
  <p>I can't predict the name of the field. is it even possible ?</p>