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Unmarshalling Dynamo DB stream data to Json format

由 青春壹個敷衍的年華 提交于 2019-12-09 02:19:29

I am able to resolve it by 

var s = JSON.stringify(data.NewImage);
   s =  s.replace('"B":', '"S":');
   parserd_json = JSON.parse(s);
   unmarshalleddata = aws.DynamoDB.Converter.unmarshall(parserd_json);

If any one has any better solution. Please suggest.

The issue appears to be that the unmarshall function expects binary B values to already be a Buffer instance for some reason. If it is a string what it actually does is encodes the string as a Buffer containing the string's utf8 bytes.

To work around it in my project what I did was:

npm install deep-for-each

import * as deepForEach from 'deep-for-each';
import { DynamoDB } from 'aws-sdk';

export function eventImageUnmarhall(data: DynamoDB.AttributeMap): any {

    deepForEach(data, replaceBinaryBase64WithBuffer);
    return DynamoDB.Converter.unmarshall(data);
}

function replaceBinaryBase64WithBuffer(value: any, key: string | number, subject: any) {
    if (key === 'B' && typeof value === "string") {
        subject[key] = Buffer.from(<string>value, 'base64');
    }
}

Then you use it like this:

import {eventImageUnmarhall} from './dynamo-helpers';

//
//…
//

let unmarshalledData = eventImageUnmarhall(data.NewImage);
标签
javascript
node.js
amazon-dynamodb
aws-sdk-js
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