How to use RestTemplate.exchange for different subclasses

Question

I have an Abstract base class A, and 2 subclasses (B and C) inherit from A.

Now I am currently using RestTemplate exchange to retrieve a list of objects from a REST API endpoint. But those objects can be either B or C. How do I do this using RestTemplate? The following if my code

ResponseEntity<B> response = restTemplate.exchange(
                endpointURL,
                HttpMethod.GET,
                request,
                new ParameterizedTypeReference<B>() {} );

Above is for B, but the responseEntity can be either B or C.

Answer 1

If your A class is abstract RestTemplate won't be able to instantiate it. There are possible solutions:

• Make A not abstract. You will be able to get A instance as a response but all of the B and C specific fields will be missed.
• Use String or Jackson's JsonNode as a response type and then manually check the properties to make sure that response is B or C and create your B / C instance using Jackson's ObjectMapper .