DynamoDb查詢枚舉

Question

我是dynamoDB的新手，這個問題可能是青少年問題。

我正在嘗試從表中查詢項目，但dynamo api無法將查詢json結果轉換為類實例，因為類中存在枚舉變量成員。

我的課程結構：[請注意，RequestStage是Enum成員]

@DynamoDBTable(tableName = "LoadInfoProvider")
@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public final class LoadInfoProvider {

/** The load request ID. */
@DynamoDBRangeKey
private String loadRequestID;

/** The load request creation id. */
@DynamoDBHashKey
private String loadRequestCreationId;

/** The carrier ID. */
private String carrierID;

/** The carrier pool. */
private String carrierPool;

/** The carrier details. */
private CarrierDetail carrierDetails;

/** The driver assignment required. */
private Boolean driverAssignmentRequired;

/** The driver pool. */
private String driverPool;

/** The trailer attachment required. */
private Boolean trailerAttachmentRequired;

/** The request type. */
private String requestType;

/** The request stage. */
private RequestStage requestStage;

/** The created time. */
private String createdTime;

/** The consumed time. */
private String consumedTime;

/** The provider status. */
private String providerStatus;

/** The is consumed. */
private Boolean isConsumed;

/** The request status. */
private RequestStatus requestStatus;

/** The trip. */
private Trip trip;
}

RequestStageEnum：

@NoArgsConstructor
@AllArgsConstructor(access = AccessLevel.PUBLIC)
@DynamoDBDocument
public enum RequestStage {

/** The initiated. */
INITIATED("initiated"),

/** The passed. */
PASSED("passed"),

/** The failed. */
FAILED("failed");

/** The value. */
@Getter
@Setter
private String value;

}

當我從該表中查詢某些內容時，出現以下錯誤。

線程“主”中的異常com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMappingException：無法在com.amazonaws.services.dynamodbv2.datamodeling.ConversionSchemas $ StandardItemConverter.createObject（ConversionSchemas.java:614）處實例化類的新實例。 .amazonaws.services.dynamodbv2.datamodeling.ConversionSchemas $ StandardItemConverter.unconvert（ConversionSchemas.java:414）位於com.amazonaws.services.dynamodbv2.datamodeling.unmarshallers.ObjectUnmarshaller.unmarshall（ObjectUnmarshaller.com.at:54） .dynamodbv2.datamodeling.unmarshallers.NullableUnmarshaller.unmarshall（NullableUnmarshaller.java:46）位於com.amazonaws.services.dynamodbv2.datamodeling.ConversionSchemas $ StandardItemConverter.unmarshall（ConversionSchemasmodelzon.data.zon.dy.na.dy.com。 .ConversionSchemas $ StandardItemConverter.unconvert（ConversionSchemas.java:426）在com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper.privateMarshallIntoObject（D ynamoDBMapper.java:630）在com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper.marshallIntoObjects（DynamoDBMapper.java:661）在com.amazonaws.services.dynamodbv2.datamodeling.PaginatedQueryList。（PaginatedQueryList。位於com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper.query（DynamoDBMapper.java:1844）的amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper.java:1856 com.amazon.optimus.dynamoHelper.DynamoDBUtil.main（DynamoDBUtil.java:164）上的queryRecord（DynamoDBUtil.java:112）原因：java.lang.InstantiationException：java.lang上的com.amazon.optimus.enums.RequestStage。 com.amazonaws.services.dynamodbv2.datamodeling.ConversionSchemas $ StandardItemConverter.createObject（ConversionSchemas.java:611）上的Class.newInstance（Class.java:427）... 12更多原因：java.lang.NoSuchMethodException：com.amazon JA的java.lang.Class.getConstructor0（Class.java:3082）的.optimus.enums.RequestStage。（） va.lang.Class.newInstance（Class.java:412）...還有13個

從異常可以明顯看出，java無法實例化枚舉。 我如何解決這個問題並使它正常工作？ 非常感謝您的幫助。

Answer 1

您需要使用@DynamoDBMarshalling注釋字段requestStage 。

假設RequestStage是一個enum ，則封送員可能是這樣的：

    public class RequestStageMarshaller implements DynamoDBMarshaller<RequestStage> {

        @Override
        public String marshall(RequestStage requestStage) {
            return requestStage.toString();
        }

        @Override
        public RequestStage unmarshall(Class<RequestStage> clazz, String 
requestStage) {
            return RequestStage.valueOf(requestStage);
        }

    }

然后，您可以這樣注釋您的requestStage字段：

@DynamoDBMarshalling(marshallerClass = RequestStageMarshaller.class)
private RequestStage requestStage