Annotation to make Jackson interpret field either as JSON array or JSON object

Question

I have this model:

class Platform {
   private List<ACL> acl;
}

Whereas the source from the server can be

{ "acl" : [{ "id" : 1 }, { "id" : 2 }] } 

or just a single Object

{ "acl" : "{ "id" : 1 } } 

Is there a way to program Jackson to interpret field either as JSON array or JSON object?