How to instruct Jackson to serialize a field inside an Object instead of the Object it self?

Question

I have an Item class. There's an itemType field inside of that class which is of type ItemType.

roughly, something like this.

class Item {    int id;    ItemType itemType; }  class ItemType {    String name;    int somethingElse; } 

When I am serializing an object of type Item using Jackson ObjectMapper, it serializes the object ItemType as a sub-object. Which is expected, but not what I want.

{   "id": 4,     "itemType": {     "name": "Coupon",     "somethingElse": 1   } } 

What I would like to do is to show the itemType's name field instead when serialized.

Something like below.

{   "id": 4,     "itemType": "Coupon" } 

Is there anyway to instruct Jackson to do so?

Answer 1

Check out @JsonValue annotation.

EDIT: like this:

class ItemType {   @JsonValue   public String name;    public int somethingElse; } 

Answer 2

You need to create and use a custom serializer.

public class ItemTypeSerializer extends JsonSerializer<ItemType>  {     @Override     public void serialize(ItemType value, JsonGenerator jgen,                      SerializerProvider provider)                      throws IOException, JsonProcessingException      {         jgen.writeString(value.name);     }  }  @JsonSerialize(using = ItemTypeSerializer.class) class ItemType {     String name;     int somethingElse; }