GoogleCloudPlatform · nitesh-55 · Sep 10, 2025
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+# Using Google Cloud Pub/Sub on App Engine Standard Java 21 Environment
+
+<a href="https://console.cloud.google.com/cloudshell/open?git_repo=https://github.com/GoogleCloudPlatform/java-docs-samples&page=editor&open_in_editor=appengine-java21/pubsub/README.md">
+<img alt="Open in Cloud Shell" src ="http://gstatic.com/cloudssh/images/open-btn.png"></a>
+
+This sample demonstrates how to use [Google Cloud Pub/Sub][pubsub]
+from [Google App Engine standard environment][ae-docs].
+
+[pubsub]: https://cloud.google.com/pubsub/docs/
+[ae-docs]: https://cloud.google.com/appengine/docs/java/
+
+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.
+
+## Clone the sample app
+
+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-java21/ee8/pubsub
+```
+
+## Setup
+
+- Make sure [`gcloud`](https://cloud.google.com/sdk/docs/) 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](https://cloud.google.com/docs/authentication/getting-started) authentication
+- [Enable](https://console.cloud.google.com/launcher/details/google/pubsub.googleapis.com) 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://<your-project-id>.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://<your-project-id>.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](https://console.cloud.google.com/iam-admin/iam) UI.
+`--push-auth-token-audience` is optional. If set, remember to modify the audience field check in [PubSubAuthenticatedPush.java](src/main/java/com/example/appengine/pubsub/PubSubAuthenticatedPush.java#L48).
+
+```
+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
+```
+
+## Run locally
+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
+```
+
+## Send fake subscription push messages with:
+
+```
+   curl -H "Content-Type: application/json" -i --data @sample_message.json
+   "localhost:8080/pubsub/push?token=<your-token>"
+```
+
+### Authenticated push notifications
+
+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>"
+```
+
+## Deploy
+
+Update the environment variables `PUBSUB_TOPIC` and `PUBSUB_VERIFICATION_TOKEN` in
+[`appengine-web.xml`](src/main/webapp/WEB-INF/appengine-web.xml),
+then:
+
+```
+   mvn clean package appengine:deploy
+```
+
+Direct your browser to `https://project-id.appspot.com`.
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+<!--
+  Copyright 2017 Google LLC
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+-->
+<!-- [START project] -->
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <packaging>war</packaging>
+  <version>1.0-SNAPSHOT</version>
+  <groupId>com.example.appengine</groupId>
+  <artifactId>appengine-pubsub</artifactId>
+
+  <!--
+    The parent pom defines common style checks and testing strategies for our samples.
+    Removing or replacing it should not affect the execution of the samples in anyway.
+  -->
+  <parent>
+    <groupId>com.google.cloud.samples</groupId>
+    <artifactId>shared-configuration</artifactId>
+    <version>1.2.0</version>
+  </parent>
+
+  <properties>
+    <maven.compiler.target>1.8</maven.compiler.target>
+    <maven.compiler.source>1.8</maven.compiler.source>
+    <failOnMissingWebXml>false</failOnMissingWebXml>    <!-- REQUIRED -->
+  </properties>
+
+  <!-- [START dependencies] -->
+  <!--  Using libraries-bom to manage versions.
+  See https://github.com/GoogleCloudPlatform/cloud-opensource-java/wiki/The-Google-Cloud-Platform-Libraries-BOM -->
+  <dependencyManagement>
+    <dependencies>
+      <dependency>
+        <groupId>com.google.cloud</groupId>
+        <artifactId>libraries-bom</artifactId>
+        <version>26.28.0</version>
+        <type>pom</type>
+        <scope>import</scope>
+      </dependency>
+    </dependencies>
+  </dependencyManagement>
+
+  <dependencies>
+    <dependency>
+      <groupId>com.google.cloud</groupId>
+      <artifactId>google-cloud-pubsub</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>com.google.cloud</groupId>
+      <artifactId>google-cloud-datastore</artifactId>
+    </dependency>
+    <!-- [END dependencies] -->
+    <dependency>
+      <groupId>javax.servlet</groupId>
+      <artifactId>javax.servlet-api</artifactId>
+      <version>3.1.0</version>
+      <type>jar</type>
+      <scope>provided</scope>
+    </dependency>
+    <dependency>
+      <groupId>com.googlecode.jatl</groupId>
+      <artifactId>jatl</artifactId>
+      <version>0.2.3</version>
+    </dependency>
+    <!-- [START dependencies] -->
+  </dependencies>
+  <!-- [END dependencies] -->
+  <build>
+    <!-- for hot reload of the web application -->
+    <outputDirectory>${project.build.directory}/${project.build.finalName}/WEB-INF/classes</outputDirectory>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-war-plugin</artifactId>
+        <version>3.4.0</version>
+      </plugin>
+      <plugin>
+        <groupId>com.google.cloud.tools</groupId>
+        <artifactId>appengine-maven-plugin</artifactId>
+        <version>2.5.0</version>
+        <configuration>
+          <!-- deploy configuration -->
+          <projectId>GCLOUD_CONFIG</projectId>
+          <version>GCLOUD_CONFIG</version>
+        </configuration>
+      </plugin>
+      <!-- for local testing of web application -->
+      <plugin>
+        <groupId>org.eclipse.jetty</groupId>
+        <artifactId>jetty-maven-plugin</artifactId>
+        <version>9.4.53.v20231009</version>
+      </plugin>
+    </plugins>
+  </build>
+</project>
+<!-- [END project] -->
@@ -0,0 +1 @@
+{"message":{"data":"dGVzdA==","attributes":{},"messageId":"91010751788941","publishTime":"2017-09-25T23:16:42.302Z"}}
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+/*
+ * Copyright 2017 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.appengine.pubsub;
+
+/**
+ * A message captures information from the Pubsub message received over the push endpoint and is
+ * persisted in storage.
+ */
+public class Message {
+  private String messageId;
+  private String publishTime;
+  private String data;
+
+  public Message(String messageId) {
+    this.messageId = messageId;
+  }
+
+  public String getMessageId() {
+    return messageId;
+  }
+
+  public void setMessageId(String messageId) {
+    this.messageId = messageId;
+  }
+
+  public String getPublishTime() {
+    return publishTime;
+  }
+
+  public void setPublishTime(String publishTime) {
+    this.publishTime = publishTime;
+  }
+
+  public String getData() {
+    return data;
+  }
+
+  public void setData(String data) {
+    this.data = data;
+  }
+}
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+/*
+ * Copyright 2017 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.appengine.pubsub;
+
+import java.util.List;
+
+public interface MessageRepository {
+
+  /** Save message to persistent storage. */
+  void save(Message message);
+
+  /**
+   * Retrieve most recent stored messages.
+   *
+   * @param limit number of messages
+   * @return list of messages
+   */
+  List<Message> retrieve(int limit);
+
+  /** Save claim to persistent storage. */
+  void saveClaim(String claim);
+
+  /**
+   * Retrieve most recent stored claims.
+   *
+   * @param limit number of messages
+   * @return list of claims
+   */
+  List<String> retrieveClaims(int limit);
+
+  /** Save token to persistent storage. */
+  void saveToken(String token);
+
+  /**
+   * Retrieve most recent stored tokens.
+   *
+   * @param limit number of messages
+   * @return list of tokens
+   */
+  List<String> retrieveTokens(int limit);
+}
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		{"message":{"data":"dGVzdA==","attributes":{},"messageId":"91010751788941","publishTime":"2017-09-25T23:16:42.302Z"}}