The return value of an enumeration variable may be empty！

[jouzitong]

I discovered during actual application that when the enumeration of the return value is empty, an exception is thrown.

Caused by: com.fasterxml.jackson.databind.exc.InvalidFormatException: Cannot coerce empty String ("") to `xyz.felh.okx.v5.enumeration.TriggerPxType` value (but could if coercion was enabled using `CoercionConfig`)
 at [Source: (okio.RealBufferedSource$inputStream$1); line: 1, column: 625] (through reference chain: ai.zzt.okx.okx_client.client.vo.RList["data"]->java.util.ArrayList[0]->ai.zzt.okx.okx_client.client.resp.AlgoOrder["slTriggerPxType"])
    at com.fasterxml.jackson.databind.exc.InvalidFormatException.from(InvalidFormatException.java:67) ~[jackson-databind-2.15.4.jar:2.15.4]
    at com.fasterxml.jackson.databind.DeserializationContext.reportBadCoercion(DeserializationContext.java:1817) ~[jackson-databind-2.15.4.jar:2.15.4]
    at com.fasterxml.jackson.databind.deser.std.StdDeserializer._checkCoercionFail(StdDeserializer.java:1662) ~[jackson-databind-2.15.4.jar:2.15.4]
    at com.fasterxml.jackson.databind.deser.std.EnumDeserializer._deserializeAltString(EnumDeserializer.java:364) ~[jackson-databind-2.15.4.jar:2.15.4]
    at com.fasterxml.jackson.databind.deser.std.EnumDeserializer._fromString(EnumDeserializer.java:279) ~[jackson-databind-2.15.4.jar:2.15.4]
    at com.fasterxml.jackson.databind.deser.std.EnumDeserializer.deserialize(EnumDeserializer.java:248) ~[jackson-databind-2.15.4.jar:2.15.4]
    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:129) ~[jackson-databind-2.15.4.jar:2.15.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:314) ~[jackson-databind-2.15.4.jar:2.15.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:177) ~[jackson-databind-2.15.4.jar:2.15.4]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer._deserializeFromArray(CollectionDeserializer.java:359) ~[jackson-databind-2.15.4.jar:2.15.4]

[jouzitong]

You can refer to the registerModule method in com.fasterxml.jackson.databind.ObjectMapper. Enumeration values can be processed uniformly here. I simply implemented a Module interface, you can also refer to it:

public class CustomEnumModule extends SimpleModule {

    public CustomEnumModule() {
        addDeserializer(Enum.class, new StatusDeserializer());
    }

    private static class StatusDeserializer extends JsonDeserializer<Enum> {
        @Override
        public Enum deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
            JsonNode node = p.getCodec().readTree(p);
            if (node.isNull()) {
                return null; // Return UNKNOWN for null value
            }
            String value = node.asText();
            if (value==null||value.isEmpty()) {
                return null; // Return UNKNOWN for empty value
            }

            Object currentValue = ctxt.getParser().getParsingContext().getCurrentValue();
            String currentName = ctxt.getParser().getParsingContext().getCurrentName();
            Class<?> valueClass = currentValue.getClass();
            Class<?> type;
            try {
                Field declaredField = valueClass.getDeclaredField(currentName);
                type = declaredField.getType();
            } catch (NoSuchFieldException e) {
                throw new RuntimeException(e);
            }
            if (!type.isEnum()) {
                throw new RuntimeException("type is not enum");
            }
            Class<Enum> enumClass = (Class<Enum>) type;

            Enum[] enumConstants = enumClass.getEnumConstants();
            for (Enum enumConstant : enumConstants) {
                if (enumConstant.name().equals(value)) {
                    return enumConstant;
                }
            }
            return null;
        }
    }
}

[forestwanglin]

I cannot reproduce what you sent above.

I get slTriggerPxType = null even if I pass slTriggerPxType: 'ABC' that is not a value of TriggerPxType.

Could you please paste your case there?

[jouzitong]

OkxApiService uses ObjectMapper when serializing objects. That problem also lies in serialization, so the main problem is to solve the enumeration serialization problem. Look at the example below：

 public static ObjectMapper defaultObjectMapper() {
        ObjectMapper mapper = new ObjectMapper();
        mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
        mapper.setPropertyNamingStrategy(PropertyNamingStrategies.SNAKE_CASE);
        return mapper;
    }

    public static void main(String[] args) throws JsonProcessingException {
        ObjectMapper objectMapper = defaultObjectMapper();
        Order order = objectMapper.readValue("{\"tpTriggerPxType\": \"\"}", Order.class);
        System.out.println(order);
    }

In this example, the same error can also be prompted.

[jouzitong]

The interface I implemented specifically is as follows: https://www.okx.com/docs-v5/zh/?shell#order-book-trading-algo-trading-get-algo-order-list. This interface will have many parameters, and there will also be many null-valued parameters.

[forestwanglin]

I tested it using websocket at first so I cannot reproduce your case.

I've fixed this issue in version 0.3.2024051001 when using rest api by adding configuration as below.

mapper.configure(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_AS_NULL, true);

The enumeration field will be set to NULL if any unknown string value, including "".