===== Google Cloud Platform =====





==== Goolge App Engine ====

=== Maven ===
== Deploy the app to the Google server== 
<code>
mvn appengine:update
</code>
After deployment the app will be available under: PROJECTAME.appspot.com

== Start local development server== 
<code>
mvn appengine:devserver
</code>
available under localhost:8080/SERVLET/PATH/FROM/WEB/XML

e.g. http://localhost:8080/rest/

== Stops the server== 
<code>
mvn appengine:devserver_stop
</code>

=== Project ===
Use the HelloWorld project from here:
https://cloud.google.com/appengine/docs/java/

Create a Project on the "Google App Engine" using the online console:
https://console.cloud.google.com/project


=== Servlets ===
Inherit from **HttpServlet**.
Registered in **webapp/WEB-INF/web.xml**
<code>
  <servlet>
    <servlet-name>query</servlet-name>
    <servlet-class>de.projectname.servlet.QueryDbExamplesServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>query</servlet-name>
    <url-pattern>/rest/query/*</url-pattern>
  </servlet-mapping>
</code>

==== Google Datastore ====
The documentation for the datastore can be found here:
https://cloud.google.com/datastore/docs/how-to


=== Spring boots with datastore ===
The Codelabs tutorial about creation of a new Spring boot application for app engine
https://codelabs.developers.google.com/codelabs/cloud-app-engine-springboot/#0


=== Datastore dependencies ===
The maven dependencies are listed here
<code>
<dependency>
  <groupId>com.google.cloud</groupId>
  <artifactId>google-cloud-datastore</artifactId>
  <version>1.28.0</version>
</dependency>
</code>
https://cloud.google.com/datastore/docs/reference/libraries

For the time of writing - it is important to reference Guava directly.
Otherwise there will be MethodNotFOund exceptions, because wrong versions of Guava are referenced by transitive dependencies.
<code>
        <!--
            VERY IMPORTANT  the right version of Guava must be referenced here.
            Otherwise there will be a "NoSuchMethodException", because of transitive dependencies to older Guava libs.

        -->
        <dependency>                        <!-- Google Core Libraries for Java -->
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>  <!-- https://github.com/google/guava/wiki -->
            <version>23.0</version>
        </dependency>
</code>


=== Enable APIs ===
Enable the APIs like "Google Cloud Datastore API", as stated in the BookShelf application

https://github.com/GoogleCloudPlatform/getting-started-java/tree/master/bookshelf


=== Enable Web Credentials ===
The web credentials must be enabled, so that one can reach the API from the URS like 
  * http://PROJECTID.appspot.com
  * http://localhost:8080

How to do so is stated in the bookshelf example too:
https://github.com/GoogleCloudPlatform/getting-started-java/tree/master/bookshelf


=== Datastore usage ===

Create a JSON key using the online console: https://console.cloud.google.com/project/_/apiui/credential

Download the key e.g. as projectiname-e1234567891.p12 and put it into your WEB-INF folder, e.g. into Keys subfolder: \\
WEB-INF/keys/projectiname-e1234567891.json

<sxh java>
	public static final String PROJECT_ID = "projectiname";
	public static final String PATH_TO_JSON_KEY = "/WEB-INF/keys/projectiname-e1234567891.json";


	public static Datastore initDataStore(GenericServlet servlet) {
		try {
			URL theurl = servlet.getServletContext().getResource(PATH_TO_JSON_KEY);
			File file = new File(theurl.toURI());
			FileInputStream fileInputStreamKey = new FileInputStream(file);

			return DatastoreOptions.builder().projectId(PROJECT_ID)
					.authCredentials(AuthCredentials.createForJson(fileInputStreamKey)).build().service();
		} catch (URISyntaxException | IOException e1) {
			return null;
		}
	}
</sxh>

Now you can query the DB:

<sxh java>
			Datastore datastore = initDataStore(servlet);
			
			Builder queryBuilder = Query.entityQueryBuilder()
			.kind(FILM_DATA_KEY);

			// filter if imdbId is given
			if(imdbId!=null && !imdbId.isEmpty()){
				String imdbUrl = String.format("http://www.imdb.com/title/%s/", imdbId.replace("/", ""));
				Filter imdbUrlFilter =	PropertyFilter.eq("imdbUrl", imdbUrl);
				queryBuilder.filter(imdbUrlFilter);
			}
			
			// sort
			queryBuilder.orderBy(OrderBy.asc("created"));
			
			Query<Entity> query = queryBuilder.build();
			Iterator<Entity> iterator = datastore.run(query);
</sxh>


=== index ===
To query the DB an index for the queried Entity properties must be created. Here the properties are:
  * imdbUrl
  * created

The index is created in a index.yaml file, which is:
  * put into the WEB-INF folder
  * deployed together with the app

Example index.yaml
<code>
indexes:

- kind: FilmData
  ancestor: no
  properties:
  - name: imdbUrl
  - name: created
    direction: asc
</code>


=== appengine-web.xml ===
Dexcribes the app:

<code>
<appengine-web-app xmlns="http://appengine.google.com/ns/1.0">
	<application>projectiname</application>
	<version>1</version>
	<threadsafe>true</threadsafe>
	<system-properties>
		<property name="java.util.logging.config.file" value="WEB-INF/logging.properties" />
	</system-properties>
	<static-files>
		<include path="/static/">
			<http-header name="Access-Control-Allow-Origin" value="*" />
		</include>
	</static-files>
</appengine-web-app>
</code>


=== Logging ===
Described in a WEB-INF/logging.properties

<code>
# Set the default logging level for all loggers to WARNING
.level = INFO
</code>

The logs are visible in the console window, where the server is running.


==== Run in Intellij Idea ====
To run a Google App Engine applicaiton locally - use the "Google Cloud Tools" plugin.

{{https://lh3.googleusercontent.com/-e52Kv6jTYic/WxkCVjuO2iI/AAAAAAAAAKs/H6qhDysp7LA_6nr4B4NEQ1nEXuy_1YbBACHMYCw/s0/2018-06-07_12-00-58.png}}

After that a new launch configuration will be created:
{{https://lh3.googleusercontent.com/-ybUh61AVhvU/WxkCmUriifI/AAAAAAAAAK0/Kv-DZ1GFH_cSzMI4Ng0FAvIOvGZKpUutwCHMYCw/s0/2018-06-07_12-02-06.png}}


=== Importing a Gradle project to Idea ===


   * Import from github, directly via the Idea, via "VCS > Checkout from Version COntrol" as stated here https://github.com/GoogleCloudPlatform/google-cloud-intellij/issues/2027
   * add to Project Structure > Modules > youtube4kidz > youtube4kidz_main via "add" the item "Google App Engin Standard" if necessary
   * first build the project completele. Building is not part of the appengine-start process: build > rebuild project. Or you will receive a ClassNotFound / MethodNotFound
   * then start project via Run "Google AppEngine Dev"




==== gcloud  ====
The gcloud command-line interface is the primary CLI tool to create and manage Google Cloud resources.

Installation
https://cloud.google.com/sdk/docs/quickstart#deb