DynamoDbMapper: support additional/dynamic attributes on declared models

[estebistec]

Jackson has a feature whereby with @AnyGetter [1] and @AnySetter annotations a serializable bean can handle JSON properties that aren't accounted for in the modeled properties (while keeping the benefits of the defined model).

Currently, with DynamoDbMapper this is only supported with a fully custom marshaller. However, this means that you've lost the benefit of modeling the known attributes and their constraints. This is true for both table models and for embedded document models. Is it reasonable for DynamoDb to perhaps have a feature like Jackson's, to support documents that could have unknown data attributes (especially helpful for embedded JSON "blobs").

I'm not against working on a pull request when I can make the time, but I wanted to get the suggestion logged now.

Thanks!

[1] http://wiki.fasterxml.com/JacksonFeatureAnyGetter

[fernomac]

👍

[zhangzhx]

Thanks for reaching out to us and this is really a nice feature for DynamoDB Mapper. You are welcome to send us a PR and we'll be glad to take a look.

[yairzaslavsky]

@estebistec -
Won't @DynamoDBTypeConvertedJson annotation over a field that is map in your entity bean help in what you want to achieve?

[estebistec]

@yairzaslavsky that looks like it'd only work if you were okay with storing the entire object as a blob. The hope was to have the mapper still use dynamodb record attributes, but both for modeled and dynamic fields.

[yairzaslavsky]

@estebistec
I think I understand - if I use json terminology - if we use the annotation you suggested you end up with an internal map which will be serialized to run record.
What you want on the other hand is have the entries of the map (let's say 5 entries) being "serialized" as 5 separate records, similar to the Embeddable concept of Hibernate. Am I correct here?

[estebistec]

Err, no, not five records. One object is still one record (or embedded object in a containing record). I just want them to be discrete attributes (or fields) instead of one big JSON string.

[yairzaslavsky]

@estebistec

Yes! This is what I meant - 5 attributes ! Sorry for my confusion :)
A record is a row, I obviously meant 5 fields (5 columns ).

Thanks for explaining

[estebistec]

No problem! As you can tell, this hasn't risen to the top of my To-Do list yet :/

[yairzaslavsky]

I don't mind assisting with implementing a pull request for this.

[yairzaslavsky]

@estebistec

May I suggest that for the map field you will have for example something like this?

@DynamoDbEmbeddable
Map<String,Object> properties;

or use the "Annotation on getter" convention?
And have only one annotation and not two annotation as in the
case of the Jackson example you gave?

[yairzaslavsky]

This is just the beginning of my work on this issue.

DynamoDBFlattened looks similar to your request.

[satz03]

do we have a solution for this in DynamoDBMapper yet? I want a particular item to have one attribute that comes from an inner class which uses @DynamoDBDocument ,so it's saved as a json object, but the class needs to be pre-defined with attributes , I want that class to take any JsonObject actually,any suggestion?