WebSockets samples for Java

appengine/websockets/README.md

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+# App Engine Flexible Environment - Web Socket Example
+This sample demonstrates how to use [Websockets](https://tools.ietf.org/html/rfc6455) on [Google App Engine Flexible Environment](https://cloud.google.com/appengine/docs/flexible/java/) using Java.
+The sample uses the [JSR-356](https://www.jcp.org/en/jsr/detail?id=356) Java API for the Websocket [client](https://mvnrepository.com/artifact/org.eclipse.jetty.websocket/javax-websocket-client-impl).
+
+## Sample application workflow
+
+1. The sample application creates a server socket using the endpoint  `/echo`.
+1. The homepage (`/`) provides a form to submit a text message to the server socket. This creates a client-side socket
+and sends the message to the server.
+1. The server on receiving the message, echoes the message back to the client.
+1. The message received by the client is stored  in an in-memory cache and is viewable on the homepage.
+
+The sample also provides a Javascript [client](src/main/webapp/js_client.jsp)(`/js_client.jsp`) that you can use to test against the Websocket server.
+
+## Setup
+
+ - [Install](https://cloud.google.com/sdk/) and initialize GCloud SDK. This will
+ ```
+    gcloud init
+ ```
+-  If this is your first time creating an app engine application
+  ```
+    gcloud appengine create
+  ```
+
+## Local testing
+
+Run using the [Jetty Maven plugin](http://www.eclipse.org/jetty/documentation/9.4.x/jetty-maven-plugin.html).
+```
+mvn jetty:run
+```
+You can then direct your browser to `http://localhost:8080/`
+
+To test the Javascript client, access `http://localhost:8080/js_client.jsp`
+
+## App Engine Flex Deployment
+
+#### `app.yaml` Configuration
+
+App Engine Flex deployment configuration is provided in [app.yaml](src/main/appengine/app.yaml).
+
+Set the environment variable `JETTY_MODULES_ENABLE:websocket` to enable the Jetty websocket module on the Jetty server.
+
+Manual scaling is set to a single instance as we are using an in-memory cache of messages for this sample application.
+
+For more details on configuring your `app.yaml`, please refer to [this resource](https://cloud.google.com/appengine/docs/flexible/nodejs/configuring-your-app-with-app-yaml).
+
+#### Deploy
+
+The sample application is packaged as a war, and hence will be automatically run using the [Java 8/Jetty 9 with Servlet 3.1 Runtime](https://cloud.google.com/appengine/docs/flexible/java/dev-jetty9).
+
+```
+  mvn appengine:deploy
+```
+You can then direct your browser to `https://YOUR_PROJECT_ID.appspot.com/`
+
+To test the Javascript client, access `https://YOUR_PROJECT_ID.appspot.com/js_client.jsp`

appengine/websockets/pom.xml

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+<!--
+  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.
+-->
+<project>
+  <modelVersion>4.0.0</modelVersion>
+  <version>1.0-SNAPSHOT</version>
+  <groupId>com.example.flexible</groupId>
+  <artifactId>websocket</artifactId>
+  <packaging>war</packaging>
+
+  <parent>
+  <groupId>com.google.cloud</groupId>
+  <artifactId>appengine-flexible</artifactId>
+    <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.version>9.4.4.v20170414</jetty.version>
+  </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 maven-websocket-jsr356] -->
+    <!--Jetty JSR-356 Websocket client side dependency-->
+    <dependency>
+      <groupId>org.eclipse.jetty.websocket</groupId>
+      <artifactId>javax-websocket-client-impl</artifactId>
+      <version>${jetty.version}</version>
+    </dependency>
+    <!-- [END maven-websocket-jsr356] -->
+    <!--Optional dependency for SettableFuture, see com.example.flexible.websocket.jsr356.ServerSocket -->
+    <dependency>
+      <groupId>com.google.guava</groupId>
+      <artifactId>guava</artifactId>
+      <version>20.0</version>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <!-- for hot reload of the web application -->
+    <outputDirectory>${project.build.directory}/${project.build.finalName}/WEB-INF/classes
+    </outputDirectory>
+    <plugins>
+      <!-- for deployment of web application -->
+      <plugin>
+        <groupId>com.google.cloud.tools</groupId>
+        <artifactId>appengine-maven-plugin</artifactId>
+        <version>${appengine.maven.plugin}</version>
+        <configuration>
+        </configuration>
+      </plugin>
+      <!-- for local testing of web application -->
+      <plugin>
+        <groupId>org.eclipse.jetty</groupId>
+        <artifactId>jetty-maven-plugin</artifactId>
+        <version>${jetty.version}</version>
+      </plugin>
+    </plugins>
+  </build>
+</project>

appengine/websockets/src/main/appengine/app.yaml

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+# 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.
+
+runtime: java
+env: flex
+manual_scaling:
+  instances: 1
+
+handlers:
+- url: /.*
+  script: this field is required, but ignored
+
+env_variables:
+  JETTY_MODULES_ENABLE: websocket
+
+
+# For applications which can take advantage of session affinity                                                                                                                      
+# (where the load balancer will attempt to route multiple connections from  
+# the same user to the same App Engine instance), uncomment the folowing:
+
+# network:
+#   session_affinity: true
+

appengine/websockets/src/main/java/com/example/flexible/websocket/jsr356/ClientSocket.java

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+/*
+ * 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.
+ */
+
+package com.example.flexible.websocket.jsr356;
+
+import com.google.common.util.concurrent.SettableFuture;
+
+import java.net.URI;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.concurrent.ConcurrentLinkedDeque;
+import java.util.concurrent.ExecutionException;
+import java.util.logging.Logger;
+import javax.websocket.ClientEndpoint;
+import javax.websocket.CloseReason;
+import javax.websocket.ContainerProvider;
+import javax.websocket.OnClose;
+import javax.websocket.OnError;
+import javax.websocket.OnMessage;
+import javax.websocket.OnOpen;
+import javax.websocket.Session;
+import javax.websocket.WebSocketContainer;
+
+/**
+ * Web socket client example using JSR-356 Java WebSocket API. Sends a message to the server, and
+ * stores the echoed messages received from the server.
+ */
+@ClientEndpoint
+public class ClientSocket {
+
+  private static final Logger logger = Logger.getLogger(ClientSocket.class.getName());
+
+  // stores the messages in-memory.
+  // Note : this is currently an in-memory store for demonstration,
+  // not recommended for production use-cases.
+  private static Collection<String> messages = new ConcurrentLinkedDeque<>();
+
+  private SettableFuture<Boolean> future = SettableFuture.create();
+  private Session session;
+
+  ClientSocket(URI endpointUri) {
+    try {
+      WebSocketContainer container = ContainerProvider.getWebSocketContainer();
+      session = container.connectToServer(this, endpointUri);
+    } catch (Exception e) {
+      throw new RuntimeException(e);
+    }
+  }
+
+  @OnOpen
+  public void onOpen(Session session) {
+    future.set(true);
+  }
+
+  /**
+   * Handles message received from the server.
+   * @param message server message in String format
+   * @param session current session
+   */
+  @OnMessage
+  public void onMessage(String message, Session session) {
+    logger.fine("Received message from server : " + message);
+    messages.add(message);
+  }
+
+  boolean waitOnOpen() throws InterruptedException, ExecutionException {
+    // wait on handling onOpen
+    boolean opened = future.get();
+    logger.fine("Connected to server");
+    return opened;
+  }
+
+  @OnClose
+  public void onClose(CloseReason reason, Session session) {
+    logger.fine("Closing Web Socket: " + reason.getReasonPhrase());
+  }
+
+  void sendMessage(String str) {
+    try {
+      // Send a message to the server
+      logger.fine("Sending message : " + str);
+      session.getAsyncRemote().sendText(str);
+    } catch (Exception e) {
+      logger.severe("Error sending message : " + e.getMessage());
+    }
+  }
+
+  // Retrieve all received messages.
+  public static Collection<String> getReceivedMessages() {
+    return Collections.unmodifiableCollection(messages);
+  }
+
+  @OnError
+  public void logErrors(Throwable t) {
+    logger.severe(t.getMessage());
+  }
+}

appengine/websockets/src/main/java/com/example/flexible/websocket/jsr356/SendServlet.java

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+/*
+ * 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.
+ */
+
+package com.example.flexible.websocket.jsr356;
+
+import com.google.common.base.Preconditions;
+import java.io.IOException;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.util.logging.Logger;
+import javax.servlet.annotation.WebServlet;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import org.eclipse.jetty.http.HttpStatus;
+
+@WebServlet("/send")
+/** Servlet that converts the message sent over POST to be over websocket. */
+public class SendServlet extends HttpServlet {
+
+  private Logger logger = Logger.getLogger(SendServlet.class.getName());
+  private final String webSocketAddress = ServerSocket.getWebSocketAddress();
+  private ClientSocket clientSocket;
+
+  private void initializeWebSocket() throws Exception {
+    clientSocket = new ClientSocket(new URI(webSocketAddress));
+    clientSocket.waitOnOpen();
+    logger.info("REST service: open websocket client at " + webSocketAddress);
+  }
+
+  private void sendMessageOverWebSocket(String message) throws Exception {
+    if (clientSocket == null) {
+      try {
+        initializeWebSocket();
+      } catch (URISyntaxException e) {
+        e.printStackTrace();
+      }
+    }
+    clientSocket.sendMessage(message);
+  }
+
+  @Override
+  public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
+    String message = request.getParameter("message");
+    Preconditions.checkNotNull(message);
+    try {
+      sendMessageOverWebSocket(message);
+      response.sendRedirect("/");
+    } catch (Exception e) {
+      e.printStackTrace(response.getWriter());
+      response.setStatus(HttpStatus.INTERNAL_SERVER_ERROR_500);
+    }
+  }
+}