DynamoDb查询枚举

Question

我是dynamoDB的新手，这个问题可能是青少年问题。

我正在尝试从表中查询项目，但dynamo api无法将查询json结果转换为类实例，因为类中存在枚举变量成员。

我的课程结构：[请注意，RequestStage是Enum成员]

@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;

}

当我从该表中查询某些内容时，出现以下错误。

线程“主”中的异常com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMappingException：无法在com.amazonaws.services.dynamodbv2.datamodeling.ConversionSchemas $ StandardItemConverter.createObject（ConversionSchemas.java:614）处实例化类的新实例。 .amazonaws.services.dynamodbv2.datamodeling.ConversionSchemas $ StandardItemConverter.unconvert（ConversionSchemas.java:414）位于com.amazonaws.services.dynamodbv2.datamodeling.unmarshallers.ObjectUnmarshaller.unmarshall（ObjectUnmarshaller.com.at:54） .dynamodbv2.datamodeling.unmarshallers.NullableUnmarshaller.unmarshall（NullableUnmarshaller.java:46）位于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。位于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）...还有13个

从异常可以明显看出，java无法实例化枚举。 我如何解决这个问题并使它正常工作？ 非常感谢您的帮助。

Answer 1

您需要使用@DynamoDBMarshalling注释字段requestStage 。

假设RequestStage是一个enum ，则封送员可能是这样的：

    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，您可以这样注释您的requestStage字段：

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