Question

使用Custom Marshall将枚举类映射到DynamoDB对象非常简单。但是如何映射枚举列表？

枚举类

public enum Transport {
SMS,EMAIL,ALL;
}

DynamoDB映射器

public class Campaign{
   private List<Transport> transport;

   @DynamoDBAttribute(attributeName = "transport")
   public List<Transport> getTransport() {
       return transport;
   }

   public void setTransport(List<Transport> transport) {
      this.transport = transport;
   }
}

Answer 1

不推荐使用DynamoDBMarshaller。请改用DynamoDBTypeConverter。

示例：

枚举类

public static enum ValidationFailure {
    FRAUD, GENERAL_ERROR
}

DynamoDBTable类

 @DynamoDBTable(tableName = "receipt")
public class Receipt {

    private Long id;
    private List<ValidationFailure> validation;

    @DynamoDBHashKey(attributeName = "id")
    public Long getId() {
        return id;
    }

    @DynamoDBTypeConverted(converter = ValidationConverter.class)
    public List<ValidationFailure> getValidation() {
        return validation;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public void setValidation(List<ValidationFailure> validation) {
        this.validation = validation;
    }
}

转换器：

public class ValidationConverter implements DynamoDBTypeConverter<List<String>, List<ValidationFailure>> {

@Override
public List<String> convert(List<ValidationFailure> object) {
    List<String> result = new ArrayList<String>();
    if (object != null) {
        object.stream().forEach(e -> result.add(e.name()));
    }
    return result;
}

@Override
public List<ValidationFailure> unconvert(List<String> object) {
    List<ValidationFailure> result = new ArrayList<ValidationFailure>();
    if (object != null) {
        object.stream().forEach(e -> result.add(ValidationFailure.valueOf(e)));
    }
    return result;
}
}

Answer 2

它对我有用，我用过Set

@DynamoDBTyped(DynamoDBMapperFieldModel.DynamoDBAttributeType.SS)
var roles: MutableSet<Employee.Role>? = null

我认为对于DynamoDBAttributeType.L的List，同样的方法也适用

Answer 3

我自己找到了答案。我在下面创建了一个自定义的马歇尔。

public class TransportMarshaller implements DynamoDBMarshaller<List<Transport>> {

@Override
public String marshall(List<Transport> transports) {
    List<String>transportMap=new ArrayList<>();
    for(Transport transport:transports){
        transportMap.add(transport.name());
    }
    return transportMap.toString().replaceAll("\\[|\\]", "");//Save as comma separate value for the purpose of easiness to unmarshall
}

@Override
public List<Transport> unmarshall(Class<List<Transport>> aClass, String s) {
    List<String>map= Arrays.asList(s.split("\\s*,\\s*")); //split from comma and parse to List
    List<Transport>transports=new ArrayList<>();
    for (String st:map){
        transports.add(Transport.valueOf(st));
    }
    return transports;
}
}

DynamoDB映射枚举列表

3 个答案: