java DynamoDB - 对象到属性值
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DynamoDB - Object to AttributeValue
提问by BPm
I'm aware of DynamoDBMapper but in my case I can't use it because I don't know all the attributes beforehand.
我知道 DynamoDBMapper，但就我而言，我无法使用它，因为我事先不知道所有属性。
I have a JSON and it's parsed to a map of objects by using Hymansonparser:
我有一个 JSON，它使用Hymanson解析器解析为对象映射：
Map<String, Object> userData = mapper.readValue(new File("user.json"), Map.class);
Looping through each attribute, how can I convert the value to AttributeValuegiven that DynamoDB AttributeValuesupports Boolean, String, Number, Bytes, List, etc.
循环遍历每个属性，AttributeValue如果 DynamoDBAttributeValue支持布尔值、字符串、数字、字节、列表等，我如何将值转换为
Is there an efficient way to do this? Is there a library for this already? My naive approach is to check if each value is of type Boolean/String/Number/etc. and then call the appropriate AttributeValuemethod, e.g: new AttributeValue().withN(value.toString())- which gives me long lines of if, else if
有没有一种有效的方法来做到这一点？已经有图书馆了吗？我天真的方法是检查每个值是否属于布尔/字符串/数字/等类型。然后调用适当的AttributeValue方法，例如：new AttributeValue().withN(value.toString())- 这给了我很长的行if, else if
回答by BPm
Finally figured out by looking at how AWS parses the JSON
Basically, this is the code:
基本上，这是代码：
Item item = new Item().withJSON("document", jsonStr);
Map<String,AttributeValue> attributes = InternalUtils.toAttributeValues(item);
return attributes.get("document").getM();
Very neat.
非常整洁。
回答by Harsh
Following is a simple solution which can be applied to convert any DynamoDB Json to Simple JSON.
以下是一个简单的解决方案，可用于将任何 DynamoDB Json 转换为简单 JSON。
//passing the reponse.getItems()
public static Object getJson(List<Map<String,AttributeValue>> mapList) {
List<Object> finalJson= new ArrayList();
for(Map<String,AttributeValue> eachEntry : mapList) {
finalJson.add(mapToJson(eachEntry));
}
return finalJson;
}
//if the map is null then it add the key and value(string) in the finalKeyValueMap
public static Map<String,Object> mapToJson(Map<String,AttributeValue> keyValueMap){
Map<String,Object> finalKeyValueMap = new HashMap();
for(Map.Entry<String, AttributeValue> entry : keyValueMap.entrySet())
{
if(entry.getValue().getM() == null) {
finalKeyValueMap.put(entry.getKey(),entry.getValue().getS());
}
else {
finalKeyValueMap.put(entry.getKey(),mapToJson(entry.getValue().getM()));
}
}
return finalKeyValueMap;
}
This will produce your desired Json in the form of List<Map<String,Object>>which is subset of the object.
这将生成您想要的 Json，其形式List<Map<String,Object>>是object.
回答by Jay Patel
I used HymansonConverterImplto convert JsonNodeto Map<String, AttributeValue>
我使用HymansonConverterImpl转换JsonNode为Map<String, AttributeValue>
ObjectMapper objectMapper = new ObjectMapper();
JsonNode jsonNode = objectMapper.readValue(jsonString, JsonNode.class);
final HymansonConverter converter = new HymansonConverterImpl();
Map<String, AttributeValue> map = converter.jsonObjectToMap(jsonNode);
Hope this helps!
希望这可以帮助！
Thanks, Jay
谢谢，杰
