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# login with your google credentials
# you will be asked to either use an existing project or create a new one
# for this article, I created the project hello-spring-cloud-gcp
$ gcloud init

# enable the Pub/Sub API
$ gcloud services enable pubsub.googleapis.com

# create a new Pub/Sub topic
$ gcloud pubsub topics create hello-pubsub

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# create a new service account with a descriptive name
# I chose 'hello-spring-cloud-gcp-app' for mine, but it can be any name you like
# just know that a service account name must be between 6 and 30 characters (inclusive), must begin with
# a lowercase letter, and consist of lowercase alphanumeric characters that can be separated by hyphens.
$ gcloud iam service-accounts create hello-spring-cloud-gcp-app

# add the appropriate roles to your service account
# for more info on roles, check https://cloud.google.com/iam/docs/understanding-roles
# for our app, we only need the Pub/Sub Publisher and Subscriber roles

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/**
 * Send a message to Pub/Sub.
 */
public <T> ListenableFuture<String> publish(String topic, T payload);

/**
 * Add a callback method to an existing subscription.
 */
public Subscriber subscribe(String subscription, Consumer<BasicAcknowledgeablePubsubMessage> messageConsumer);

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public abstract class PubSubConsumer {

    /**
     * Name of an existing Pub/Sub subscription.
     */
    public abstract String subscription();

    /**
     * The actual consumer logic.
     *

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@Component
public class HelloPubSubConsumer extends PubSubConsumer {

    private static final Logger LOGGER = LoggerFactory.getLogger(HelloPubSubConsumer.class);

    @Override
    public String subscription() {
        return "hello-pubsub-subscription";
    }

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@Configuration
public class HelloPubSubSubscriberConfig {

    private static final Logger LOGGER = LoggerFactory.getLogger(HelloPubSubSubscriberConfig.class);

    private final PubSubTemplate pubSubTemplate;

    private final HelloPubSubConsumer helloPubSubConsumer;

    @Autowired

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s.SpringCloudGcpPubSubExampleApplication : Started SpringCloudGcpPubSubExampleApplication in 2.824 seconds (JVM running for 3.432)
b.c.q.s.c.HelloPubSubSubscriberConfig    : Subscribing HelloPubSubConsumer to hello-pubsub-subscription

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# list pub/sub topics (in case you don't remeber the your topic's name)
$ gcloud pubsub topics list

# setting up topic (just for readability purposes)
$ PUBSUB_TOPIC=projects/hello-spring-cloud-gcp/topics/hello-pubsub

# publish to topic
$ gcloud pubsub topics publish ${PUBSUB_TOPIC}\
    --message "Hello, Pub/Sub"

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public abstract class PubSubPublisher {

    private static final Logger LOGGER = LoggerFactory.getLogger(PubSubPublisher.class);

    private final PubSubTemplate pubSubTemplate;

    protected PubSubPublisher(PubSubTemplate pubSubTemplate) {
        this.pubSubTemplate = pubSubTemplate;
    }

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@Component
public class HelloPubSubPublisher extends PubSubPublisher {

    @Autowired
    public HelloPubSubPublisher(PubSubTemplate pubSubTemplate) {
        super(pubSubTemplate);
    }

    @Override
    protected String topic() {