Question

Suppose I have a json object that looks like:

  {
    id: 1,
    name: "john doe"
    spouse: 2
  }

and the class I want it to deserialize it to:

class Person{

  private Long id;
  private String name;

  private Person spouse;

  //getters/setters
}

Is there any way to tell jackson to expand the spouse: 2 property into a new Person POJO with id=2 when deserializing the JSON?

I have run into this issue as a result of deserializing JSON into persistent entities and would like to be able to easily persist the relationships between these entities.

Answer 1

Aside from a full deserializer, there is a simpler way: define a POJO with a single int-arg constructor like so:

class Person {
   int id;
   public Person(int id) {
     this.id = id;
   }
}

This actually works, as Jackson will try to find limited number of special constructors (single-arg public constructors that that take String, int, long, double or boolean).

You can optionally also denote these with @JsonCreator — and if constructor is not public, you must do it, to make it discoverable. But for public ctors this is not needed.