Calling SNS services from Lambda - aws-lambda

Question

I need help with Java AWS-Lambda.
I am working on Lambda to update the database. There is cloudwatch event trigger and invoke Lambda for an update database based on some criteria. I want to send notification as soon as DB update. I want to invoke SNS services from Lambda.
I am using SNS account which running with multi-factor authentication. Please suggest how to create/setup lambda to send SNS.
Note: I am not looking at "how to trigger Lambda from SNS". I am looking at how to send SNS from the Lambda function IN JAVA.

Answer 1

This is a simple way of publishing a message to an SNS topic using aws java sdk.
To publish message with attributes use this java code sample Publish a Message with Attributes to an Amazon SNS Topic
You basically have to use the same code in your lambda handler.
you need to grant your Lambda IAM role permissions to publish to your SNS topic using appropriate IAM Policy.
// Publish a message to an Amazon SNS topic.
final String msg = "If you receive this message, publishing a message to an Amazon SNS topic works.";
final PublishRequest publishRequest = new PublishRequest(topicArn, msg);
final PublishResult publishResponse = snsClient.publish(publishRequest);
// Print the MessageId of the message.
System.out.println("MessageId: " + publishResponse.getMessageId());
This is how i have done in my project created a helperservice and used in my lambdahandler.
// my lambda handler
public ApiGatewayResponse handleRequest(ApiGatewayRequest request, Context context) {
try {
// call to the helperservice
PublishResult publishResult = helperService.publishMessage("Message to be published to sns topic");
//return response
return buildResponse(HttpStatus.SC_OK);
} catch(Exception e) {
this.logger.error(e.getMessage(), e);
return buildResponse(e.getMessage(), HttpStatus.SC_INTERNAL_SERVER_ERROR);
}
}
// HerperService class class
public class HelperService {
private final AmazonSNS snsClient;
private final Configuration config;
#Inject
public HelperService(
AmazonSNS snsClient,
Configuration config,
) {
this.snsClient = snsClient;
this.config = config;
}
public PublishResult publishMessage(String message) {
PublishRequest publishRequest = new PublishRequest(config.getAuditSNSTopicARN(), message);
return snsClient.publish(publishRequest);
}
}