Define POJO for changing JSON responses

Question

I am using Java 8/Spring 5 to call a third-party API. I am using HttpClient which works well, and I have a POJO that works 99% of the time.

When I call this one service, the JSON looks like:

{"field1":"a",
 "field2":"b",
 "field3:"c"}

Based on different parameters it could come back as:

{"field1":"a",
 "field2":{
    "subfield1:"x",
    "subfield2:"y",
    "subfield3":"z"},
 "field3:"c"}

I am using the latest FastJacksonMapper to convert from JSON string to a Java POJO, and it works in the first instance, but not in the second instance.

I know it may be common for JSON to change based on requests, but I expect JSON to be a little more consistent.

Any thoughts on how I could tweak my POJO? Any JSON annotations I can use to fix this? Or, maybe create a separate POJO so that in case one fails, the other picks up?

Thanks!

Answer 1

So for the same URL and http method you can get different payloads? The same key "field2" might have a string value in option A and a different object in option B? IMHO that's bad design of API.

That third-party API having any description like swagger? Such description will help you generate correct POJO with proper annotations.

If such documentation is not available try to use generators like: http://www.jsonschema2pojo.org/

Answer 2

private static Either<Type1Obj, Type2Obj> getPojoFromJson(String json) {
        try {
            // Type1Obj from json
            return Either.left(obj1);
        } catch (IOException e) {
            try {
                //Type2Obj from json
                return Either.right(obj2);
            } catch (IOException e1) {
                //fallback
            }
            e.printStackTrace();
        }

        return null;
}