CODEWITHSUNDEEP
javajsonaws-sdkamazon-dynamodb-streams
Asanga Dewaguru
Asanga Dewaguru

Reputation: 1098

How to get the pure Json string from DynamoDB stream new image?

I've a Dynamodb table with streaming enabled. Also I've created a trigger for this table which calls an AWS Lambda function. Within this lambda function, I'm trying read the new image (Dynamodb item after the modification) from the Dynamodb stream and trying to get the pure json string out of it. My Question is how can i get the pure json string of the DynamoDB item that's been sent over the stream? I'm using the code snippet given below to get the new Image, but I've no clue how to get the json string out of it. Appreciate your help.

public class LambdaFunctionHandler implements RequestHandler<DynamodbEvent, Object> {

@Override
public Object handleRequest(DynamodbEvent input, Context context) {
    context.getLogger().log("Input: " + input);

    for (DynamodbStreamRecord record : input.getRecords()){

        context.getLogger().log(record.getEventID());
        context.getLogger().log(record.getEventName());
        context.getLogger().log(record.getDynamodb().toString());
        Map<String,AttributeValue> currentRecord = record.getDynamodb().getNewImage();

        //how to get the pure json string of the new image
        //..............................................
     }
     return "Successfully processed " + input.getRecords().size() + " records.";
}

}

Upvotes: 17

Views: 20929

Answers (8)

saiyam jain
saiyam jain

Reputation: 1

Below is the Method which converts DynamoDB JSON to normal JSON

/**
 * Converts DynamoDB JSON to normal JSON.
 *
 * @param map Input map of String to AttributeValue.
 * @return Returns an ObjectNode containing the normal JSON.
 */

public JsonObject toJsonObject(final Map<String, AttributeValue> map) {
        final JsonNode result = mapToJsonObject(map);
        final ObjectNode objectNode = (ObjectNode) result;
        final ObjectMapper objectMapper = new ObjectMapper();
        String recordObjectString;
        try {
            recordObjectString = objectMapper.writeValueAsString(objectNode);
        } catch (JsonProcessingException e) {
            throw new RuntimeException(e);
        }
        final JsonParser jsonParser = new JsonParser();
        final JsonObject jsonObject = jsonParser.parse(recordObjectString)
                                                .getAsJsonObject();
        return jsonObject;
    }

So in your Case simple call below method like this

// here record is of type DynamodbStreamRecord

toJsonObject(record.getDynamodb().getNewImage());

Upvotes: 0

jthreja
jthreja

Reputation: 11

For the ones facing issues with AttributeValue conversion refer the below code: https://github.com/aws/aws-lambda-java-libs/blob/master/aws-lambda-java-events-sdk-transformer/README.md

Map<String, AttributeValue> stringAttributeValueMap = DynamodbAttributeValueTransformer.toAttributeValueMapV1(dynamodb.getNewImage());

            List stringAttributeValueMapList = new ArrayList();
            stringAttributeValueMapList.add(stringAttributeValueMap);
            List<Item> listOfItem = InternalUtils.toItemList(stringAttributeValueMapList);
            Gson gson = new GsonBuilder().setPrettyPrinting().create();
            String updatedJSON = gson.toJson(listOfItem.get(0).asMap());

Upvotes: 0

blacelle
blacelle

Reputation: 2217

For those stuck with a Map<String, ?> where objects are plain Map, but not Attributes value, you can do the following:

Map<String, AttributeValue> dynamoDbAttributes = 
    objectMapper.convertValue(dynamoDbMap, new TypeReference<Map<String, AttributeValue>>() {});

and then convert this DynamoDB Map into a plain Map (equivalent to the json originally pushed into DynamoDb):

asMap = InternalUtils.toSimpleMapValue(dynamoDbAttributes);

Upvotes: 0

lost in binary
lost in binary

Reputation: 562

Just summarizing the answer of Himanshu Parmar:

Map<String, AttributeValue> newImage = record.getDynamodb().getNewImage();
List<Map<String, AttributeValue>> listOfMaps = new ArrayList<Map<String, AttributeValue>>();
listOfMaps.add(newImage);
List<Item> itemList = ItemUtils.toItemList(listOfMaps);
for (Item item : itemList) {
    String json = item.toJSON();
}

Upvotes: 3

Guru
Guru

Reputation: 175

In c# you can convert newImage to pure json by use of DynamoDB Document class

using Amazon.DynamoDBv2.DocumentModel;

var streamRecord = dynamoEvent.Records.First();

var jsonResult=Document.FromAttributeMap(streamRecord.Dynamodb.NewImage).ToJson();

and if you want to go further ahead to convert json to object you can use Newtonsoft

using Newtonsoft.Json;

TModel model = JsonConvert.DeserializeObject(jsonResult);

Upvotes: 4

Himanshu Parmar
Himanshu Parmar

Reputation: 437

Below is the complete code for converting from Dynamo JSON to Standard JSON:

import com.amazonaws.services.dynamodbv2.document.Item;
import com.amazonaws.services.dynamodbv2.document.internal.InternalUtils;
import com.amazonaws.services.dynamodbv2.model.AttributeValue;
import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.RequestHandler;
import com.amazonaws.services.lambda.runtime.events.DynamodbEvent;
import com.amazonaws.services.lambda.runtime.events.DynamodbEvent.DynamodbStreamRecord;
import com.google.gson.Gson;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

/**
 * Main Lambda class to receive event stream, parse it to Survey
 * and process them.
 */
public class SurveyEventProcessor implements
        RequestHandler<DynamodbEvent, String> {

    private static final String INSERT = "INSERT";

    private static final String MODIFY = "MODIFY";

    public String handleRequest(DynamodbEvent ddbEvent, Context context) {

        List<Item> listOfItem = new ArrayList<>();
        List<Map<String, AttributeValue>> listOfMaps = null;
        for (DynamodbStreamRecord record : ddbEvent.getRecords()) {

            if (INSERT.equals(record.getEventName()) || MODIFY.equals(record.getEventName())) {
                listOfMaps = new ArrayList<Map<String, AttributeValue>>();
                listOfMaps.add(record.getDynamodb().getNewImage());
                listOfItem = InternalUtils.toItemList(listOfMaps);
            }

            System.out.println(listOfItem);
            try {
               // String json = new ObjectMapper().writeValueAsString(listOfItem.get(0));
                Gson gson = new Gson();
                Item item = listOfItem.get(0);

                String json = gson.toJson(item.asMap());
                System.out.println("JSON is ");
                System.out.println(json);
            }catch (Exception e){
                e.printStackTrace();
            }
        }


        return "Successfully processed " + ddbEvent.getRecords().size() + " records.";
    }
}

Upvotes: 9

Marcus Ataide
Marcus Ataide

Reputation: 7530

This library do the job: dynamoDb-marshaler

var unmarshalJson = require('dynamodb-marshaler').unmarshalJson;

console.log('jsonItem Record: %j', unmarshalJson(record.dynamodb.NewImage));

Upvotes: -4

shailender arya
shailender arya

Reputation: 31

Found a way of doing it cleanly. Using InternalUtils from aws-java-sdk-dynamodb-1.11.15.jar

com.amazonaws.services.dynamodbv2.model.Record streamRecord = ((RecordAdapter) record).getInternalObject();
            // get order ready //
            OrderFinal order = Utils.mapO2Object(
                    InternalUtils.toSimpleMapValue(streamRecord.getDynamodb().getNewImage().get("document").getM()), 
                    OrderFinal.class );

Upvotes: 3

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