我在请求的主体中有以下 JSON 对象：
**JSON**
    {
        "nombre": "example",
        "number": 100,
        "listOfMeasurables": {
              "measurableOne": {
                  "positionOne": [0,3,0],
                  "positionTwo": [0,3,0]
              },
              "measurableTwo": {
                  "positionOne": [0,3]
              }
        }
    }
现在我有一个抽象类 Measurable，以及 MeasurableOne、MeasurableTwo 和 MeasurableThree 类，它们都继承自 Measurable。
**Measurable**
    public abstract class Measurable {
        public abstract String getType();
    }
**MeasurableOne**
    public class MeasurableOne extends Measurable {
        protected int [] positionOne;
        protected int [] positionTwo;
        public MeasurableOne(int [] positionOne, int [] positionTwo) {
            this.positionOne = positionOne;
            this.positionTwo = positionTwo;
        }
        @Override
        public String getType() {
            return "MeasurableOne";
        }
    }
**MeasurableTwo**
    public class MeasurableTwo extends Measurable {
        protected int [] positionOne;
        public MeasurableTwo(int [] positionOne) {
            this.positionOne = positionOne;
        }
        @Override
        public String getType() {
            return "MeasurableTwo";
        }
    }
**MeasurableThree**
    public class MeasurableThree extends Measurable {
        protected int [] positionOne;
        protected int [] positionTwo;
        protected int [] positionThree;
        public MeasurableThree(int [] positionOne, int [] positionTwo, int [] positionThree) {
            this.positionOne = positionOne;
            this.positionTwo = positionTwo;
            this.positionThree = positionThree;
        }
        @Override
        public String getType() {
            return "MeasurableThree";
        }
    }
现在，我有一个控制器，将接收此 JSON。listOfMeasurables 数组可以包含 measurableOne、measurableTwo、measurableThree 中的任意一个，也可以是其中的 1、2 或 3 个，顺序任意。如何让控制器知道可测量对象的类型，以便创建相应的对象？
    @PostMapping(path = "/createActivity")
    public ResponseEntity<String> createActivity(@RequestBody Activity activity) { // 在这里
    }
非常感谢您的帮助！谢谢

public class Activity {
    private String nombre;
    private Integer number;
    private ListOfMeasurables listOfMeasurables;
    // getter and setter
}
public class ListOfMeasurables {
    private MeasurableOne measurableOne;
    private MeasurableTwo measurableTwo;
    private MeasurableThree measurableThree;
    // getter and setter
}