This sample demonstrates how to use Google Cloud Pub/Sub from Google App Engine standard environment.

The home page of this application provides a form to publish messages using Google/Cloud PubSub. The application then receives these published messages over a push subscription endpoint and then stores in Google Cloud Datastore. The home page provides a view of the most recent messages persisted in storage.

Copy the sample apps to your local machine, and cd to the pubsub directory:

git clone https://github.com/GoogleCloudPlatform/java-docs-samples
cd java-docs-samples/appengine-java8/pubsub

• Make sure gcloud is installed and initialized:

   gcloud init

• If this is the first time you are creating an App Engine project

   gcloud app create

• For local development, set up authentication

• Enable Pub/Sub API

• Create a topic

gcloud pubsub topics create <your-topic-name>

• Create a push subscription, to send messages to a Google Cloud Project URL such as https://.appspot.com/push.

The verification token is used to ensure that the end point only handles requests that are sent matching the verification token. You can use uuidgen on MacOS X, Windows, and Linux to generate a unique verification token.

gcloud pubsub subscriptions create <your-subscription-name> \
  --topic <your-topic-name> \
  --push-endpoint \
  https://<your-project-id>.appspot.com/pubsub/push?token=<your-verification-token> \
  --ack-deadline 30

• Create a subscription for authenticated pushes to send messages to a Google Cloud Project URL such as https://.appspot.com/authenticated-push.

The push auth service account must have Service Account Token Creator Role assigned, which can be done in the Cloud Console IAM & admin UI. --push-auth-token-audience is optional. If set, remember to modify the audience field check in PubSubAuthenticatedPush.java.

gcloud pubsub subscriptions create <your-subscription-name> \
  --topic <your-topic-name> \
  --push-endpoint \
    https://<your-project-id>.appspot.com/pubsub/authenticated-push?token=<your-verification-token> \
  --ack-deadline 30 \
  --push-auth-service-account=[your-service-account-email] \
  --push-auth-token-audience=example.com

Set the following environment variables and run using shown Maven command. You can then direct your browser to http://localhost:8080/

export PUBSUB_TOPIC=<your-topic-name>
export PUBSUB_VERIFICATION_TOKEN=<your-verification-token>
mvn appengine:run

   curl -H "Content-Type: application/json" -i --data @sample_message.json
   "localhost:8080/pubsub/push?token=<your-token>"

Simulating authenticated push requests will fail because requests need to contain a Cloud Pub/Sub-generated JWT in the "Authorization" header.

   curl -H "Content-Type: application/json" -i --data @sample_message.json
   "localhost:8080/pubsub/authenticated-push?token=<your-token>"

Update the environment variables PUBSUB_TOPIC and PUBSUB_VERIFICATION_TOKEN in appengine-web.xml, then:

   mvn clean package appengine:deploy

Direct your browser to https://project-id.appspot.com.