background:
there is a member variable f in the model (Request) that receives client requests, which needs to be instantiated into different instances (An or B) for different business types (type).

    public abstract class Father {
    }
    public class A extends Father {
        private String a1;
        private String a2;
    }
    public class B extends Father {
        private String b1;
        private String b2;
    }
    public class Request {
        private Father f;
        private String type; // typefAB
    }

the current solution is to receive it directly with a JSONObject in the request model, and then convert it to a concrete instance.

public class Request {
    private JSONObject f;
    private String type; // typefAB
}

excuse me, how to configure (or how to do) in springboot so that the code of json- > A can be omitted? I cast it directly into a concrete instance in the rest of the business.
or is there any other better solution to deal with similar problems?

Thank you all for your generous advice.