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 [native Jetty WebSocket Server API](http://www.eclipse.org/jetty/documentation/9.4.x/jetty-websocket-server-api.html) to create a server-side socket

and the [native Jetty WebSocket Client API](http://www.eclipse.org/jetty/documentation/9.4.x/jetty-websocket-client-api.html).

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.

- [Install](https://cloud.google.com/sdk/) and initialize GCloud SDK. This will

```

```

- If this is your first time creating an app engine application

```

```

Run using the [Jetty Maven plugin](http://www.eclipse.org/jetty/documentation/9.4.x/jetty-maven-plugin.html).

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 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).

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).

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`

Note: This application constructs a Web Socket URL using `getWebSocketAddress`

in the [SendServlet Class](src/main/java/com/example/flexible/websocket/jettynative/SendServlet.java)

. The application assumes the latest version of the service.

<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>

<groupId>org.eclipse.jetty.demo</groupId>

<artifactId>native-jetty-websocket-example</artifactId>

<version>1.0-SNAPSHOT</version>

<packaging>war</packaging>

<!--

<parent>

<groupId>com.google.cloud.samples</groupId>

<artifactId>shared-configuration</artifactId>

<version>1.0.10</version>

</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>

<!-- To run websockets client -->

<dependency>

<groupId>org.eclipse.jetty.websocket</groupId>

<artifactId>websocket-client</artifactId>

<version>${jetty.version}</version>

</dependency>

<dependency>

<groupId>org.eclipse.jetty.websocket</groupId>

<artifactId>websocket-servlet</artifactId>

<version>${jetty.version}</version>

<scope>provided</scope>

</dependency>

<dependency>

<groupId>com.google.guava</groupId>

<artifactId>guava</artifactId>

<version>23.0</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>

runtime: java

env: flex

manual_scaling:

instances: 1

handlers:

- url: /.*

script: this field is required, but ignored

env_variables:

JETTY_MODULES_ENABLE: websocket

package com.example.flexible.websocket.jettynative;

import java.util.Collection;

import java.util.Collections;

import java.util.concurrent.ConcurrentLinkedDeque;

import java.util.logging.Logger;

import org.eclipse.jetty.websocket.api.Session;

import org.eclipse.jetty.websocket.api.annotations.OnWebSocketClose;

import org.eclipse.jetty.websocket.api.annotations.OnWebSocketConnect;

import org.eclipse.jetty.websocket.api.annotations.OnWebSocketMessage;

import org.eclipse.jetty.websocket.api.annotations.WebSocket;

@WebSocket(maxTextMessageSize = 64 * 1024)

public class ClientSocket {

private Logger logger = Logger.getLogger(ClientSocket.class.getName());

private Session session;

// 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<>();

@OnWebSocketClose

public void onClose(int statusCode, String reason) {

logger.fine("Connection closed: " + statusCode + ":" + reason);

this.session = null;

}

@OnWebSocketConnect

public void onConnect(Session session) {

this.session = session;

}

@OnWebSocketMessage

public void onMessage(String msg) {

logger.fine("Message Received : " + msg);

messages.add(msg);

}

// Retrieve all received messages.

public static Collection<String> getReceivedMessages() {

return Collections.unmodifiableCollection(messages);

}

}

package com.example.flexible.websocket.jettynative;

import javax.servlet.annotation.WebServlet;

import org.eclipse.jetty.websocket.servlet.WebSocketServlet;

import org.eclipse.jetty.websocket.servlet.WebSocketServletFactory;

@SuppressWarnings("serial")

@WebServlet(name = "Echo WebSocket Servlet", urlPatterns = { "/echo" })

public class EchoServlet extends WebSocketServlet {

@Override

public void configure(WebSocketServletFactory factory) {

factory.register(ServerSocket.class);

}

}