step-5-notify-user-about-generated-invoice.md

Step 5: Notify user about generated invoice

Once invoice is generated, user should receive an SMS text message about it.

Add dependency to Spring Cloud AWS SNS integration

Add a dependency to build.gradle:

implementation 'io.awspring.cloud:spring-cloud-aws-starter-sns'

Send SMS

Spring Cloud AWS comes with a high level SnsSmsOperations for sending text messages.

Update OrderListener class to send a text message. Watch LocalStack logs to see if the integration works.

snsSmsOperations.send("+48555444333", "invoice ready");

Fan-Out from SNS to SQS

To support hypothetical other listeners for OrderCreated event, instead of publishing a message directly to SQS queue, publish it instead to order-created-topic with SnsOperations.

Solution

snsOperations.sendNotification("order-created-topic", SnsNotification.of(new OrderCreated(order.getOrderId())));

On the listener side, to tell the framework that this message comes with SNS, annotate event argument in OrderListener#handle with @SnsNotificationMessage and change the queue name to order-created-queue.

Solution

@SqsListener(queueNames = "order-created-queue")
void handle(@SnsNotificationMessage OrderCreated event) {
    ...
}

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