amazon web services - AWS DynamoDB trigger using Lambda in JAVA

Question

I am trying to trigger an AWS lambda function written in Java, on dynamodb stream events. Amazon has a guide for the same, using NodeJS here http://docs.aws.amazon.com/lambda/latest/dg/wt-ddb-create-test-function.html

The testing input for NodeJS (from the above link) looks like an SNS event, so I tried to use the corresponding SNSEvent class in Java as an input to my handler method.

import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.LambdaLogger;
import com.amazonaws.services.lambda.runtime.events.SNSEvent;
import com.amazonaws.services.lambda.runtime.events.SNSEvent.SNSRecord;
import java.util.List;

public class RecomFunction {

    public void handler(SNSEvent event, Context context) {

        LambdaLogger logger = context.getLogger();

        List<SNSRecord> records = event.getRecords();

        if (records != null) {
            for (SNSRecord record : records) {
                if (record != null) {
                    logger.log("SNS record: " + record.getSNS().getMessage());
                }
            }
        }
    }

}

Unfortunately, record.getSNS() returns NULL resulting to a NullPointer exception

There is a related question, however a specific answer was not given: Setup DynamoDB Trigger using Lambda

Answer 1

This code worked for me. You can use it to receive and process DynamoDB events in a Lambda function -

public class Handler implements RequestHandler<DynamodbEvent, Void> {

    @Override
    public Void handleRequest(DynamodbEvent dynamodbEvent, Context context) {

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

            if (record == null) {
                continue;
            }

            // Your code here
        }

        return null;
    }
}

Similarly, you can use SNSEvent and SNSRecord to handle Amazon SNS events.