Question

我是dynamoDB的新手，这个问题可能是少年。

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。

我的类结构：[注意RequestStage是一个枚举成员]

@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;

}

当我从这个表中查询某些内容时，我收到以下错误。

线程中的异常＆＃34; main＆＃34; com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMappingException：无法实例化新的类实例在com.amazonaws.services.dynamodbv2.datamodeling.ConversionSchemas $ StandardItemConverter.createObject（ConversionSchemas.java:614）在com.amazonaws.services.dynamodbv2.datamodeling.ConversionSchemas $ StandardItemConverter.unconvert（ConversionSchemas.java:414）在com.amazonaws.services.dynamodbv2.datamodeling.unmarshallers.ObjectUnmarshaller.unmarshall（ObjectUnmarshaller.java:54）在com.amazonaws.services.dynamodbv2.datamodeling.unmarshallers.NullableUnmarshaller.unmarshall（NullableUnmarshaller.java:46）在com.amazonaws.services.dynamodbv2.datamodeling.ConversionSchemas $ StandardItemConverter.unmarshall（ConversionSchemas.java:593）在com.amazonaws.services.dynamodbv2.datamodeling.ConversionSchemas $ StandardItemConverter.unconvert（ConversionSchemas.java:426）在com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper.privateMarshallIntoObject（DynamoDBMapper.java:630）在com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper.marshallIntoObjects（DynamoDBMapper.java:661）在com.amazonaws.services.dynamodbv2.datamodeling.PaginatedQueryList。（PaginatedQueryList.java:65）在com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper.query（DynamoDBMapper.java:1856）在com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper.query（DynamoDBMapper.java:1844）在com.amazon.optimus.dynamoHelper.DynamoDBUtil.queryRecord（DynamoDBUtil.java:112）在com.amazon.optimus.dynamoHelper.DynamoDBUtil.main（DynamoDBUtil.java:164）引起：java.lang.InstantiationException：com.amazon.optimus.enums.RequestStage 在java.lang.Class.newInstance（Class.java:427）在com.amazonaws.services.dynamodbv2.datamodeling.ConversionSchemas $ StandardItemConverter.createObject（ConversionSchemas.java:611） ......还有12个引起：java.lang.NoSuchMethodException：com.amazon.optimus.enums.RequestStage。（）在java.lang.Class.getConstructor0（Class.java:3082）在java.lang.Class.newInstance（Class.java:412） ......还有13个

从异常中可以清楚地看出，java无法实例化枚举。我如何解决这个问题并使其有效？感谢您的帮助。

Answer 1

您需要使用requestStage为您的字段@DynamoDBMarshalling添加注释。

假设RequestStage是enum，这就是你的编组员的样子：

    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);
        }

    }

然后你会像这样注释你的requestStage字段：

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

DynamoDb查询枚举

1 个答案: