我正在尝试使用DynamoDbMapper和最新的aws android sdk从dynamodb表映射json对象:com.amazonaws:aws-android-sdk-ddb-mapper:2.13.0,我看到此异常:“ DynamoDBMappingException :预期的S值...

我表中的json对象具有3个属性,其中2个是字符串,第三个是复杂对象列表。我已经使用@DynamoDbDocument注释为复杂对象创建了一个对象,并使用了正确的封送处理注释,但是它似乎并未将json对象正确封送为java对象。
复杂对象是采用以下格式的json对象:

{
  "allCitiesList": [
    {
      "city": "Auckland, New Zealand",
      "times": {
        "recTimes": [
          "Jan1",
          "Jan2"
        ]
      }
    }
}


public class CitiesDO {
    private String city;
    private String country;
    private List<AllCitiesObject> allCitiesList;
...get/setters for other fields...

    @DynamoDBMarshalling(marshallerClass =
    AllCitiesJSONMarshaller.class)
    public List<AllCitiesObject> getAllCitiesList() {
        return allCitiesList;
    }

    public void setAllCitiesList(List<AllCitiesObject> allCitiesList) {
        this.allCitiesList = allCitiesList;
    }
}


@DynamoDBDocument
public class AllCitiesObject {
    @DynamoDBAttribute(attributeName = "allCitiesList")
    private String data;

    public AllCitiesObject(){}

    public String getData() {
        return data.toString();
    }

    public void setData(String data) {
        this.data = data;
    }
}


class AllCitiesJSONMarshaller extends JsonMarshaller<AllCitiesObject> {}

还尝试过使用自定义编组器处理此方法,但没有成功:

public class MyCustomMarshaller implements DynamoDBMarshaller<List<AllCitiesObject>> {

    private static final ObjectMapper mapper = new ObjectMapper();
    private static final ObjectWriter writer = mapper.writer();

    @Override
    public String marshall(List<AllCitiesObject> obj) {

        try {
            return writer.writeValueAsString(obj);
        } catch (JsonProcessingException e) {
            throw new RuntimeException(
                    "Unable to marshall the instance of " + obj.getClass()
                            + "into a string", e);
        }
    }

    @Override
    public List<AllCitiesObject> unmarshall(Class<List<AllCitiesObject>> clazz, String json) {
        final CollectionType
                type =
                mapper.getTypeFactory().constructCollectionType(List.class, AllCitiesObject.class);
        try {
            return mapper.readValue(json, type);
        } catch (Exception e) {
            throw new RuntimeException("Unable to unmarshall the string " + json
                    + "into " + clazz, e);
        }
    }

}


例外是:
DynamoDBMappingException:期望的S值{L:[{M:{times = {M:{recTimes = {L:[{S:Jan1,},{S:Jan2,}

我很难将json解组为字符串,尽管我认为我已经正确设置了它。谁能帮助我了解我所缺少的内容以及如何解决此问题?我将衷心感谢您的帮助!

最佳答案

不推荐使用DynamoDBMarshalling,因此建议使用更新的DynamoDBTypeConverted批注。

Mapping Arbitrary Data上有一些有用的注释。

您还可以在this answer中查看我的示例

总之,您将创建一个AllCities纯Java对象。然后,您编写一个简单的转换器类,该类告诉DynamoDB如何将AllCities对象转换为字符串以进入DynamoDB。同样,转换器类告诉您的应用程序如何将字符串转换回Java对象。

07-24 09:36
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