Mapping GraphQL response to class in Java/Spring

Question

I'm having some trouble mapping a GraphQL response to a class and I'm probably missing something obvious so I need a second pair of eyes on my code I think.

I have a response that looks like this:

{
    "data": {
        "Area": [
            {
                "id": "1"
            },
            {
                "id": "2"
            }
        ]
    }
}

My consumer and client looks like this:

public class Consumer {

    private final WebClient webClient;

    private static final String QUERY = "query { Area { id }}";

    public Consumer(WebClient webClient) {
        this.webClient = webClient;
    }

    public AreaResponse.AreaData getAreas() {
        var request = new GraphQLRequest(QUERY, null);

        var res = webClient.post()
                .bodyValue(request)
                .retrieve()
                .bodyToMono(AreaResponse.class)
                .block();

        return res.getData();
    }
}

And finally my response dto:

@Data
public class AreaResponse {
    private AreaData data;

    @Data
    public class AreaData{
        private Collection<Area> Area;

        @Data
        public class Area{
            private String id;
        }
    }
}

If I map the response to String.class I get the same data as in Postman so there's nothing wrong with the query or the endpoint. But when I try to map to AreaResponse the Area object is null. I am not sure if the hierarchy in my response class is correct or if I should move the Collection a step down?

please don't use block to retrieve a value from a publisher like this. you instantly turned your application to be not reactive anymore, so you can just write it procedurally. — thinkgruen
– thinkgruen, Commented Aug 10, 2021 at 7:22

thinkgruen · Accepted Answer · 2021-08-10 08:27:17Z

1

I think the problem comes from the use of upper-case Area in the response. By default, Jackson will try to map all of the stuff to a lower-case version of the class name (or lower-camelcase).

One way to fix it:

@JsonProperty("Area")
private Collection<Area> Area;

P.S. nested/ inner classes can be static, so public static class AreaData etc.

edited Aug 10, 2021 at 8:27

answered Aug 10, 2021 at 7:51

thinkgruen

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