Question

我正在尝试从dynamoDb中获取项目。但是，当我使用partiton键获取单个项目时，一切正常，但是当我尝试使用扫描获取dynamo db中的所有项目时，我会输入错误。以下是我要做的代码：

    public List<PageCmsDomain> getAllPages() {
    DynamoDBUtil dynamoDBUtil = new DynamoDBUtil();
    AmazonDynamoDB dynamoDBClient = dynamoDBUtil.getDynamoDBClient();
    DynamoDBMapper mapper = new DynamoDBMapper(dynamoDBClient);
    List<PageCmsDomain> scanResult = mapper.scan(PageCmsDomain.class, new 
    DynamoDBScanExpression());
    return scanResult;

执行此代码时出现以下错误：

com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMappingException: PageCmsDomain[restrictions]; could not unconvert attribute
at com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapperTableModel.unconvert(DynamoDBMapperTableModel.java:271)
at com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper.privateMarshallIntoObject(DynamoDBMapper.java:456)
at com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper.marshallIntoObjects(DynamoDBMapper.java:484)
at com.amazonaws.services.dynamodbv2.datamodeling.PaginatedScanList.<init>(PaginatedScanList.java:64)
at com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper.scan(DynamoDBMapper.java:1458)
at com.amazonaws.services.dynamodbv2.datamodeling.AbstractDynamoDBMapper.scan(AbstractDynamoDBMapper.java:216)
at com.astro.ott.dynamodb.cmsapi.impl.PageCmsDaoImpl.getAllPages(PageCmsDaoImpl.java:74)
at com.astro.ott.cmsapi.impl.PageCmsGetServiceImpl.getPages(PageCmsGetServiceImpl.java:41)
at com.astro.ott.cms_api.cms_api.PageCmsTestCase.get(PageCmsTestCase.java:81)

Caused by: com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMappingException: not supported; requires @DynamoDBTyped or @DynamoDBTypeConverted
at com.amazonaws.services.dynamodbv2.datamodeling.StandardModelFactories$Rules$NotSupported.get(StandardModelFactories.java:660)
at com.amazonaws.services.dynamodbv2.datamodeling.StandardModelFactories$Rules$NotSupported.get(StandardModelFactories.java:650)
at com.amazonaws.services.dynamodbv2.datamodeling.StandardModelFactories$AbstractRule.unconvert(StandardModelFactories.java:714)
at com.amazonaws.services.dynamodbv2.datamodeling.StandardModelFactories$AbstractRule.unconvert(StandardModelFactories.java:691)
at com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBTypeConverter$DelegateConverter.unconvert(DynamoDBTypeConverter.java:109)
at com.amazonaws.services.dynamodbv2.datamodeling.StandardTypeConverters$Vector$ToMap.unconvert(StandardTypeConverters.java:433)
at com.amazonaws.services.dynamodbv2.datamodeling.StandardTypeConverters$Vector$ToMap$1.unconvert(StandardTypeConverters.java:417)
at com.amazonaws.services.dynamodbv2.datamodeling.StandardTypeConverters$Vector$ToMap$1.unconvert(StandardTypeConverters.java:410)
at com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBTypeConverter$DelegateConverter.unconvert(DynamoDBTypeConverter.java:109)
at com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBTypeConverter$NullSafeConverter.unconvert(DynamoDBTypeConverter.java:128)
at com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBTypeConverter$ExtendedConverter.unconvert(DynamoDBTypeConverter.java:88)
at com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapperFieldModel.unconvert(DynamoDBMapperFieldModel.java:146)
at com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapperFieldModel.unconvertAndSet(DynamoDBMapperFieldModel.java:164)
at com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapperTableModel.unconvert(DynamoDBMapperTableModel.java:267)
... 32

我在获取单个项目时也使用相同的PageCmsDomain。

Answer 1

仅当restrictions字段为空或空映射时，指定的代码才有效。否则它将抛出异常，因为DynamoDB不允许保存或获取具有对象类型字段的对象（即使是泛型类型，在本例中为map的值类型Object）它应该具有特定类型（例如String, Integer, Map<String, Integer>）。

如果restrictions地图的值类型无法更改为特定的值，您可以通过添加DynamoDBTypeConvertedJson注释来存储restrictions字段的序列化值来解决此问题：

@DynamoDBAttribute(attributeName = "restrictions")
@DynamoDBTypeConvertedJson
private Map<String, Object> restrictions;

另一种选择是指定您自己的自定义转换器类和注释限制字段 @DynamoDBTypeConverted(converter = CustomConverter.class)

DynamoDb扫描无法正常工作

1 个答案: