gcloud-java example using Managed VMs & SparkJava

This app demonstrates how to use [`gcloud-java`'s Datastore client](https://github.com/GoogleCloudPlatform/gcloud-java/tree/master/gcloud-java-datastore#google-cloud-java-client-for-datastore) from within an [App Engine Managed VM](https://cloud.google.com/appengine/docs/java/managed-vms/) project using [SparkJava](http://sparkjava.com/). The app allows you to create and modify a database of "users", which contains their ID, name, and email information.

`gcloud-java` is an idiomatic Java client for [Google Cloud Platform](https://cloud.google.com/) services. Read more about the library [here](https://github.com/GoogleCloudPlatform/gcloud-java#google-cloud-java-client).

Setup

1. Create a Google Developers Console project with the Datastore API enabled. [Follow these instructions](https://cloud.google.com/docs/authentication#preparation) to get your project set up. If you wish to deploy this application, you will also need to [enable billing](https://support.google.com/cloud/?rd=2#topic=6288636).

2. Set up the local development environment by [installing the Google Cloud SDK](https://cloud.google.com/sdk/) and running the following commands in command line: `gcloud auth login` and `gcloud config set project [YOUR PROJECT ID]`.

3. Ensure that you have Maven installed. See installation instructions [here](https://maven.apache.org/install.html).

Running locally

Run the application on your local machine by typing the following into your command line from the `sparkjava` directory: `mvn clean package exec:java`. Navigate to `localhost:8080` to view and interact with the application.

Deploying

If you've enabled billing (step 1 in [Setup](#Setup)), you can deploy the application to the web by running `mvn gcloud:deploy` from your command line (from the `sparkjava` directory).

How does it work?

You'll notice that the source code is split into three folders: `appengine`, `java/com/google/appengine/sparkdemo`, and `resource/public`. The `appengine` folder contains a `Dockerfile` and an `app.yaml`, necessary files to [configure the VM environment](https://cloud.google.com/appengine/docs/managed-vms/config). The `java/com/google/appengine/sparkdemo` folder contains the controller code, which uses the `gcloud-java` library to modify the records in the Google Cloud Datastore. Finally, the `resource/public` folder contains the home webpage, which uses jQuery to send HTTP requests to create, remove, and update records.

Spark runs the [`main` method](https://github.com/GoogleCloudPlatform/java-docs-samples/blob/master/managedvms/sparkjava-demo/src/main/java/com/google/appengine/sparkdemo/Main.java) upon server startup. The `main` method creates the controller, [`UserController`](https://github.com/GoogleCloudPlatform/java-docs-samples/blob/master/managedvms/sparkjava-demo/src/main/java/com/google/appengine/sparkdemo/UserController.java). The URIs used to send HTTP requests in the [home page](https://github.com/GoogleCloudPlatform/java-docs-samples/blob/master/managedvms/sparkjava-demo/src/main/resources/public/index.html) correspond to methods in the `UserController` class. For example, the `index.html` code for `create` makes a `POST` request to the path `/api/users` with a body containing the name and email of a user to add. `UserController` contains the following code to process that request:

post("/api/users", (req, res) -> userService.createUser(

req.queryParams("name"),

req.queryParams("email),

<?xml version="1.0" encoding="UTF-8"?>

<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>com.google.appengine.sparkdemo</groupId>

<artifactId>sparkdemo</artifactId>

<version>1.0</version>

<dependencies>

<dependency>

<groupId>com.sparkjava</groupId>

<artifactId>spark-core</artifactId>

<version>2.3</version>

</dependency>

<dependency>

<groupId>org.slf4j</groupId>

<artifactId>slf4j-simple</artifactId>

<version>1.7.12</version>

</dependency>

<dependency>

<groupId>com.google.code.gson</groupId>

<artifactId>gson</artifactId>

<version>2.4</version>

</dependency>

<dependency>

<groupId>junit</groupId>

<artifactId>junit</artifactId>

<version>4.12</version>

</dependency>

<dependency>

<groupId>com.google.gcloud</groupId>

<artifactId>gcloud-java</artifactId>

<version>0.1.1</version>

</dependency>

</dependencies>

<build>

<plugins>

<plugin>

<groupId>org.apache.maven.plugins</groupId>

<artifactId>maven-compiler-plugin</artifactId>

<version>2.5.1</version>

<configuration>

<source>1.8</source>

<target>1.8</target>

</configuration>

</plugin>

<plugin>

<artifactId>maven-assembly-plugin</artifactId>

<executions>

<execution>

<phase>package</phase>

<goals>

<goal>single</goal>

</goals>

</execution>

</executions>

<configuration>

<descriptorRefs>

<descriptorRef>jar-with-dependencies</descriptorRef>

</descriptorRefs>

<archive>

<manifest>

<mainClass>com.google.appengine.sparkdemo.Main</mainClass>

</manifest>

</archive>

</configuration>

</plugin>

<plugin>

<groupId>org.codehaus.mojo</groupId>

<artifactId>exec-maven-plugin</artifactId>

<version>1.4.0</version>

<configuration>

<mainClass>com.google.appengine.sparkdemo.Main</mainClass>

<arguments>

<argument>-jar</argument>

<argument>target/sparkdemo-1.0-jar-with-dependencies.jar</argument>

</arguments>

</configuration>

</plugin>

<plugin>

<groupId>com.google.appengine</groupId>

<artifactId>gcloud-maven-plugin</artifactId>

<version>2.0.9.88.v20151125</version>

<configuration>

</configuration>

</plugin>

</plugins>

</build>

</project>

FROM gcr.io/google_appengine/openjdk8

VOLUME /tmp

ADD sparkdemo-1.0-jar-with-dependencies.jar app.jar

ENTRYPOINT [ "java","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]

runtime: custom

vm: true

package com.google.appengine.sparkdemo;

import static spark.Spark.port;

import com.google.gcloud.datastore.DatastoreOptions;

public class Main {

public static void main(String[] args) {

port(8080);

UserController userController =

new UserController(new UserService(DatastoreOptions.defaultInstance().service()));

}

}

package com.google.appengine.sparkdemo;

public class ResponseError {

private String message;

public ResponseError(String message, String... args) {

this.message = String.format(message, (Object) args);

}

public ResponseError(Exception e) {

this.message = e.getMessage();

}

}

package com.google.appengine.sparkdemo;

import java.util.UUID;

public class User {

private String id;

private String name;

private String email;

public User(String name, String email) {

this(UUID.randomUUID().toString(), name, email);

}

public User(String id, String name, String email) {

this.id = id;

this.email = email;

this.name = name;

}

public String getId() {

return id;

}

public String getName() {

return name;

}

public String getEmail() {

return email;

}

void setId(String id) {

this.id = id;

}

public void setName(String name) {

this.name = name;

}

public void setEmail(String email) {

this.email = email;

}

}

package com.google.appengine.sparkdemo;

import static spark.Spark.after;

import static spark.Spark.delete;

import static spark.Spark.exception;

import static spark.Spark.get;

import static spark.Spark.post;

import static spark.Spark.put;

import com.google.gson.Gson;

import spark.ResponseTransformer;

import spark.Spark;

public class UserController {

public UserController(final UserService userService) {

Spark.staticFileLocation("/public");

get("/api/users", (req, res) -> userService.getAllUsers(), UserController::toJson);

post("/api/users",

(req, res) -> userService.createUser(req.queryParams("name"), req.queryParams("email")),

json());

put("/api/users/:id", (req, res) -> userService.updateUser(

req.params(":id"),

req.queryParams("name"),

req.queryParams("email")

), json());

delete("/api/users/:id", (req, res) -> userService.deleteUser(req.params(":id")), json());

after((req, res) -> {

res.type("application/json");

});

exception(IllegalArgumentException.class, (e, req, res) -> {

res.status(400);

res.body(toJson(new ResponseError(e)));

});

}

private static String toJson(Object object) {

return new Gson().toJson(object);

}

private static ResponseTransformer json() {

return UserController::toJson;

}

}