Can you serialize object's property instead of a whole object in Spring REST? (object being a field of a class)

To clarify - I have some class in a Spring REST project which has an instance of some other class as one of its fields.

public class Event {

...
...
...

private Location location;
}

The location object has some id of type int. So when serializing Event object is it possible to somehow only attach the location.id field instead of the whole serialized location object?

If you are allowed to modify Location class, you can try @JsonValue annotation on the Location.id field:

public class Event {
    private String someField;
    private Location location;
}

public class Location {
    @JsonValue
    private int id;
}

It will get serilized to:

{
  "someFiled": "someValue",
  "location": 122
}

If you prefer different name of the serialized field, use @JsonProperty:

public class Event {
    private String someField;

    @JsonProperty("locationId")
    private Location location;
}

public class Location {
    @JsonValue
    private int id;
}

{
  "someFiled": "someValue",
  "locationId": 122
}

Another option I can think of would be using @JsonUnwrapped in conjunction with @JsonIgnoreProperties. The Location class doesn't need to be changed in this case, but all properties to be excluded need to be explicitly listed.

public static class Event {
    private String someField;

    @JsonUnwrapped(prefix = "location_")
    @JsonIgnoreProperties({"fieldA", "fieldB", ...})
    private Location location;

}

{
  "someFiled": "someValue",
  "location_id": 122
}

> Bare in mind that both solutions will break deserialization.

If you serialize the whole Event object I believe it is not possible to avoid serializing the location object too as it is one of its properties. You could, however, attempt to serialize the properties of the object and not the object itself, in which case you could serialize location.id and not the whole location object.

The only problem is that you would have to find some way to organize this data in the file that you serialize it to, or just create a different file for each property.