Spring Rest Controller Return Specific Fields

Question

I\'ve been going through my head the best way to design a JSON API using Spring MVC. As we all know IO is expensive, and thus I don\'t want to make the client make several A

Answer 1

This can be done by Spring Projections. Also works fine with Kotlin. Take a look here: https://www.baeldung.com/spring-data-jpa-projections

Answer 2

Instead of returning a Game object, you could serialize it as as a Map<String, Object>, where the map keys represent the attribute names. So you can add the values to your map based on the include parameter.

@ResponseBody
public Map<String, Object> getGame(@PathVariable("id") long id, String include) {

    Game game = service.loadGame(id);
    // check the `include` parameter and create a map containing only the required attributes
    Map<String, Object> gameMap = service.convertGameToMap(game, include);

    return gameMap;

}

As an example, if you have a Map<String, Object> like this:

gameMap.put("id", game.getId());
gameMap.put("title", game.getTitle());
gameMap.put("publishers", game.getPublishers());

It would be serialized like this:

{
  "id": 1,
  "title": "Call of Duty Advanced Warfare",
  "publishers": [
    {
        "id": 1,
        "name": "Activision"
    }
  ]
}

Answer 3

Being aware that my answer comes quite late: I'd recommend to look at Projections.

What you're asking for is what projections are about.

Since you're asking about Spring I'd give this one a try: https://docs.spring.io/spring-data/rest/docs/current/reference/html/#projections-excerpts