How to ignore unknown fields on field level?

Question

I am using a class from another module in my request.

public class KeyInput {
  @NotNull
  private Long id;
  @NotNull
  private String startValue;
  @NotNull
  private String endValue;
}

I cannot put @JsonIgnoreProperties(ignoreUnknown = true) annotation on this class, since the module does not contain jackson library.

Putting it on field level where I used it on my request class didn't work out.

@JsonIgnoreProperties(ignoreUnknown = true)
private List<KeyInput> keys;

Here is the incoming request. Notice the source of the problem, the two fields (name and type), which are not declared in KeyInput class.

{
    "id": 166,
    "name": "inceptionDate",
    "type": "DATE",
    "startValue": "22",
    "endValue": "24"
}

How am I supposed to tell the jackson to ignore the unknown fields if the class is not in my package?

P.S: I know I can get the keys as json string and serialize it using ObjectMapper (by setting the configuration DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES to false), but I am looking for a cleaner solution here.

Also putting those fields in my class and never use it, is another dirty solution.

Answer 1

Two ways come to my mind.

Method 1

Create an empty child class that inherit from KeyInput class. This is the easiest method.

@JsonIgnoreProperties(ignoreUnknown = true)
public class InheritedKeyInput extends KeyInput{}

Method 2

Create a custom de-serializer for KeyInput class.

public class KeyInputDeserializer extends JsonDeserializer<KeyInput> {

    @Override
    public KeyInput deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException, JsonProcessingException {
        JsonNode node = jsonParser.getCodec().readTree(jsonParser);
        KeyInput keyInput = new KeyInput();
        keyInput.setId(node.get("id").asLong());
        keyInput.setEndValue(node.get("startValue").textValue());
        keyInput.setStartValue(node.get("startValue").textValue());
        return keyInput;
    }
}

Bind this de-serializer to KeyInput using a configuration class

@Configuration
public class JacksonConfig implements Jackson2ObjectMapperBuilderCustomizer {

    @Override
    public void customize(Jackson2ObjectMapperBuilder builder) {
        builder.failOnEmptyBeans(false)
                .deserializerByType(KeyInput.class, new KeyInputDeserializer());
    }
}