Adding Pub/Sub App engine Java 8 sample (#865)

* Adding Pub/Sub app engine sample

* updating README

* removing unit tests
updating README based on review

appengine-java8/pom.xml

@@ -72,6 +72,8 @@
 
     <module>postgres</module>
 
+    <module>pubsub</module>
+
     <module>requests</module>
 
     <module>remote-client</module>

appengine-java8/pubsub/README.md

@@ -0,0 +1,80 @@
+# Using Google Cloud Pub/Sub on App Engine Standard Java 8 Environment
+
+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-java8/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 beta 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 beta 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
+```
+
+## 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>"
+```
+
+## 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 appengine:deploy
+```
+
+Direct your browser to `https://project-id.appspot.com`.

appengine-java8/pubsub/pom.xml

@@ -0,0 +1,76 @@
+<!--
+  Copyright 2017 Google Inc.
+
+  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>
+  <modelVersion>4.0.0</modelVersion>
+  <packaging>war</packaging>
+  <version>1.0-SNAPSHOT</version>
+  <groupId>com.example.flexible</groupId>
+  <artifactId>appengine-pubsub</artifactId>
+
+  <parent>
+    <artifactId>appengine-java8-samples</artifactId>
+    <groupId>com.google.cloud</groupId>
+    <version>1.0.0</version>
+    <relativePath>..</relativePath>
+  </parent>
+
+  <properties>
+    <maven.compiler.target>1.8</maven.compiler.target>
+    <maven.compiler.source>1.8</maven.compiler.source>
+    <failOnMissingWebXml>false</failOnMissingWebXml> <!-- REQUIRED -->
+    <appengine.maven.plugin>1.3.1</appengine.maven.plugin>
+    <jetty>9.4.4.v20170414</jetty>
+  </properties>
+
+  <dependencies>
+    <dependency>
+      <groupId>javax.servlet</groupId>
+      <artifactId>javax.servlet-api</artifactId>
+      <version>3.1.0</version>
+      <type>jar</type>
+      <scope>provided</scope>
+    </dependency>
+
+    <!-- [START dependencies] -->
+    <dependency>
+      <groupId>com.google.cloud</groupId>
+      <artifactId>google-cloud-pubsub</artifactId>
+      <version>0.24.0-beta</version>
+    </dependency>
+    <dependency>
+      <groupId>com.google.cloud</groupId>
+      <artifactId>google-cloud-datastore</artifactId>
+      <version>1.6.0</version>
+    </dependency>
+    <!-- [END dependencies] -->
+  </dependencies>
+  <build>
+    <!-- for hot reload of the web application -->
+    <outputDirectory>${project.build.directory}/${project.build.finalName}/WEB-INF/classes</outputDirectory>
+    <plugins>
+      <plugin>
+        <groupId>com.google.cloud.tools</groupId>
+        <artifactId>appengine-maven-plugin</artifactId>
+        <version>${appengine.maven.plugin}</version>
+        <configuration>
+          <!-- deploy configuration -->
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
+</project>
+<!-- [END project] -->

appengine-java8/pubsub/sample_message.json

@@ -0,0 +1 @@
+{"message":{"data":"dGVzdA==","attributes":{},"messageId":"91010751788941","publishTime":"2017-09-25T23:16:42.302Z"}}

appengine-java8/pubsub/src/main/java/com/example/appengine/pubsub/Message.java

@@ -0,0 +1,53 @@
+/**
+ * Copyright 2017 Google Inc.
+ *
+ * <p>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
+ *
+ * <p>http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * <p>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;
+  }
+}

appengine-java8/pubsub/src/main/java/com/example/appengine/pubsub/MessageRepository.java

@@ -0,0 +1,30 @@
+/**
+ * Copyright 2017 Google Inc.
+ *
+ * <p>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
+ *
+ * <p>http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * <p>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);
+}

appengine-java8/pubsub/src/main/java/com/example/appengine/pubsub/MessageRepositoryImpl.java

@@ -0,0 +1,98 @@
+/**
+ * Copyright 2017 Google Inc.
+ *
+ * <p>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
+ *
+ * <p>http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * <p>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 com.google.cloud.datastore.Datastore;
+import com.google.cloud.datastore.DatastoreOptions;
+import com.google.cloud.datastore.Entity;
+import com.google.cloud.datastore.Key;
+import com.google.cloud.datastore.KeyFactory;
+import com.google.cloud.datastore.Query;
+import com.google.cloud.datastore.QueryResults;
+import com.google.cloud.datastore.StructuredQuery;
+import java.util.ArrayList;
+import java.util.List;
+
+/** Storage for Message objects using Cloud Datastore. */
+public class MessageRepositoryImpl implements MessageRepository {
+
+  private static MessageRepositoryImpl instance;
+
+  private String messagesKind = "messages";
+  private KeyFactory keyFactory = getDatastoreInstance().newKeyFactory().setKind(messagesKind);
+
+  @Override
+  public void save(Message message) {
+    // Save message to "messages"
+    Datastore datastore = getDatastoreInstance();
+    Key key = datastore.allocateId(keyFactory.newKey());
+
+    Entity.Builder messageEntityBuilder = Entity.newBuilder(key)
+        .set("messageId", message.getMessageId());
+
+    if (message.getData() != null) {
+      messageEntityBuilder = messageEntityBuilder.set("data", message.getData());
+    }
+
+    if (message.getPublishTime() != null) {
+      messageEntityBuilder = messageEntityBuilder.set("publishTime", message.getPublishTime());
+    }
+    datastore.put(messageEntityBuilder.build());
+  }
+
+  @Override
+  public List<Message> retrieve(int limit) {
+    // Get Message saved in Datastore
+    Datastore datastore = getDatastoreInstance();
+    Query<Entity> query =
+        Query.newEntityQueryBuilder()
+            .setKind(messagesKind)
+            .setLimit(limit)
+            .addOrderBy(StructuredQuery.OrderBy.desc("publishTime"))
+            .build();
+    QueryResults<Entity> results = datastore.run(query);
+
+    List<Message> messages = new ArrayList<>();
+    while (results.hasNext()) {
+      Entity entity = results.next();
+      Message message = new Message(entity.getString("messageId"));
+      String data = entity.getString("data");
+      if (data != null) {
+        message.setData(data);
+      }
+      String publishTime = entity.getString("publishTime");
+      if (publishTime != null) {
+        message.setPublishTime(publishTime);
+      }
+      messages.add(message);
+    }
+    return messages;
+  }
+
+  private Datastore getDatastoreInstance() {
+    return DatastoreOptions.getDefaultInstance().getService();
+  }
+
+  private MessageRepositoryImpl() {
+  }
+
+  // retrieve a singleton instance
+  public static synchronized  MessageRepositoryImpl getInstance() {
+    if (instance == null) {
+      instance = new MessageRepositoryImpl();
+    }
+    return instance;
+  }
+}