JsonMappingException: Not a map, not an array or not an enum

[Matej]

Hello,

I am working on a rest api application and i have some problems with the code. Part of code that is problematic is:

    @JsonValue

    public String serialize() throws JsonProcessingException {

        ObjectMapper mapper = new ObjectMapper();

        return mapper.writeValueAsString(this);

    }

This returns not an enum. The current object is an extend of avro schema. I also tried:

    @JsonValue

    public String serialize() throws JsonProcessingException {

        ObjectMapper mapper = new ObjectMapper();

        return mapper.writeValueAsString(getUserData());

    }

Where user data is an actual avro object. I dont understand what do these error mean. Can someone explain? Also, is there a better way to return an avro object combined with other parameters?

Thanks

[Matej]

Here is the full example:

public class PaginatedUserData extends UserDataAvro {

    @JsonValue
    public String serialize() throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();

        HashMap<String, String> map = new HashMap<>();
        map.put("test", "5");
        return mapper.writeValueAsString(map);
    }
}

Returns:

Could not write JSON: Not an array