title: Get Jackson XMLMapper to set root element name in code
body: <p>How do I get Jackson's XMLMapper to set the name of the root xml element when serializing?</p>
  
  <p>There's an annotation to do it, if you're serializing a pojo: @XmlRootElement(name="blah"). But I'm serializing a generic Java class, LinkedHashMap, so I can't use an annotation.</p>
  
  <p>There's probably some switch somewhere to set it. Poking around in Jackson code, I see a class named SerializationConfig.withRootName(), but I've no clue how to use it.</p>