Add App Engine Datastore raw APIs sample.

These samples are pulled from the "projection query" https://cloud.google.com/appengine/docs/java/datastore/projectionqueries and "structuring for strong consistency" https://cloud.google.com/appengine/docs/java/datastore/structuring_for_strong_consistency pages. I will add additional code to this sample as I convert the other pages, as well.
GoogleCloudPlatform · Apr 21, 2016 · c2091ae · c2091ae
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diff --git a/appengine/datastore/README.md b/appengine/datastore/README.md
@@ -0,0 +1,19 @@
+# Google Cloud Datastore Sample
+
+This sample demonstrates how to use [Google Cloud Datastore][java-datastore]
+from [Google App Engine standard environment][ae-docs].
+
+[java-datastore]: https://cloud.google.com/appengine/docs/java/datastore/
+[ae-docs]: https://cloud.google.com/appengine/docs/java/
+
+## Setup
+1. Update the `<application>` tag in `src/main/webapp/WEB-INF/appengine-web.xml`
+   with your project name.
+1. Update the `<version>` tag in `src/main/webapp/WEB-INF/appengine-web.xml`
+   with your version name.
+
+## Running locally
+    $ mvn appengine:devserver
+
+## Deploying
+    $ mvn appengine:update
diff --git a/appengine/datastore/pom.xml b/appengine/datastore/pom.xml
@@ -0,0 +1,114 @@
+<!--
+Copyright 2016 Google Inc. All Rights Reserved.
+
+ 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>
+  <packaging>war</packaging>
+  <version>1.0-SNAPSHOT</version>
+  <groupId>com.example.appengine</groupId>
+  <artifactId>appengine-datastore</artifactId>
+  <parent>
+    <groupId>com.google.cloud</groupId>
+    <artifactId>doc-samples</artifactId>
+    <version>1.0.0</version>
+    <relativePath>../..</relativePath>
+  </parent>
+  <dependencies>
+    <dependency>
+      <groupId>com.google.appengine</groupId>
+      <artifactId>appengine-api-1.0-sdk</artifactId>
+      <version>${appengine.sdk.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>com.google.auto.value</groupId>
+      <artifactId>auto-value</artifactId>
+      <version>1.2</version>
+      <scope>provided</scope>
+    </dependency>
+    <dependency>
+      <groupId>com.google.code.findbugs</groupId>
+      <artifactId>jsr305</artifactId> <!-- @Nullable annotations -->
+      <version>3.0.1</version>
+    </dependency>
+
+    <dependency>
+      <groupId>com.google.guava</groupId>
+      <artifactId>guava</artifactId>
+      <version>19.0</version>
+    </dependency>
+
+    <dependency>
+      <groupId>javax.servlet</groupId>
+      <artifactId>servlet-api</artifactId>
+      <type>jar</type>
+      <scope>provided</scope>
+    </dependency>
+    <dependency>
+      <groupId>joda-time</groupId>
+      <artifactId>joda-time</artifactId>
+      <version>2.9.3</version>
+    </dependency>
+
+    <!-- Test Dependencies -->
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <version>4.10</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-all</artifactId>
+      <version>1.10.19</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>com.google.appengine</groupId>
+      <artifactId>appengine-testing</artifactId>
+      <version>${appengine.sdk.version}</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>com.google.appengine</groupId>
+      <artifactId>appengine-api-stubs</artifactId>
+      <version>${appengine.sdk.version}</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>com.google.appengine</groupId>
+      <artifactId>appengine-tools-sdk</artifactId>
+      <version>${appengine.sdk.version}</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>com.google.truth</groupId>
+      <artifactId>truth</artifactId>
+      <version>0.28</version>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+  <build>
+    <!-- for hot reload of the web application -->
+    <outputDirectory>${project.build.directory}/${project.build.finalName}/WEB-INF/classes</outputDirectory>
+    <plugins>
+      <!-- Parent POM defines ${appengine.sdk.version} (updates frequently). -->
+      <plugin>
+        <groupId>com.google.appengine</groupId>
+        <artifactId>appengine-maven-plugin</artifactId>
+        <version>${appengine.sdk.version}</version>
+      </plugin>
+    </plugins>
+  </build>
+</project>
diff --git a/appengine/datastore/src/main/java/com/example/appengine/AbstractGuestbook.java b/appengine/datastore/src/main/java/com/example/appengine/AbstractGuestbook.java
@@ -0,0 +1,83 @@
+/*
+ * Copyright 2016 Google Inc. All Rights Reserved.
+ *
+ * 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.appengine;
+
+import com.example.time.Clock;
+
+import com.google.appengine.api.datastore.DatastoreService;
+import com.google.appengine.api.datastore.DatastoreServiceFactory;
+import com.google.appengine.api.datastore.Entity;
+import com.google.appengine.api.users.User;
+import com.google.appengine.api.users.UserService;
+import com.google.appengine.api.users.UserServiceFactory;
+import com.google.common.collect.ImmutableList;
+
+import java.util.Date;
+import java.util.List;
+
+/**
+ * A log of notes left by users.
+ *
+ * <p>This is meant to be subclassed to demonstrate different storage structures in Datastore.
+ */
+abstract class AbstractGuestbook {
+  private final DatastoreService datastore;
+  private final UserService userService;
+  private final Clock clock;
+
+  AbstractGuestbook(Clock clock) {
+    this.datastore = DatastoreServiceFactory.getDatastoreService();
+    this.userService = UserServiceFactory.getUserService();
+    this.clock = clock;
+  }
+
+  /**
+   * Appends a new greeting to the guestbook and returns the {@link Entity} that was created.
+   */
+  public Greeting appendGreeting(String content) {
+    Greeting greeting =
+        Greeting.create(
+            createGreeting(
+                datastore,
+                userService.getCurrentUser(),
+                clock.now().toDate(),
+                content));
+    return greeting;
+  }
+
+  /**
+   * Write a greeting to Datastore.
+   */
+  protected abstract Entity createGreeting(
+      DatastoreService datastore, User user, Date date, String content);
+
+  /**
+   * Return a list of the most recent greetings.
+   */
+  public List<Greeting> listGreetings() {
+    ImmutableList.Builder<Greeting> greetings = ImmutableList.builder();
+    for (Entity entity : listGreetingEntities(datastore)) {
+      greetings.add(Greeting.create(entity));
+    }
+    return greetings.build();
+  }
+
+  /**
+   * Return a list of the most recent greetings.
+   */
+  protected abstract List<Entity> listGreetingEntities(DatastoreService datastore);
+}
diff --git a/appengine/datastore/src/main/java/com/example/appengine/AbstractGuestbookServlet.java b/appengine/datastore/src/main/java/com/example/appengine/AbstractGuestbookServlet.java
@@ -0,0 +1,59 @@
+/*
+ * Copyright 2016 Google Inc. All Rights Reserved.
+ *
+ * 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.appengine;
+
+import java.io.IOException;
+
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+abstract class AbstractGuestbookServlet extends HttpServlet {
+  private final AbstractGuestbook guestbook;
+
+  public AbstractGuestbookServlet(AbstractGuestbook guestbook) {
+    this.guestbook = guestbook;
+  }
+
+  private void renderGuestbook(HttpServletRequest req, HttpServletResponse resp)
+      throws IOException, ServletException {
+    resp.setContentType("text/html");
+    resp.setCharacterEncoding("UTF-8");
+    req.setAttribute("greetings", guestbook.listGreetings());
+    req.getRequestDispatcher("/guestbook.jsp").forward(req, resp);
+  }
+
+  @Override
+  public void doGet(HttpServletRequest req, HttpServletResponse resp)
+      throws IOException, ServletException {
+    renderGuestbook(req, resp);
+  }
+
+  @Override
+  public void doPost(HttpServletRequest req, HttpServletResponse resp)
+      throws IOException, ServletException {
+    String content = req.getParameter("content");
+    if (content == null || content.isEmpty()) {
+      resp.sendError(HttpServletResponse.SC_BAD_REQUEST, "missing content");
+      return;
+    }
+    guestbook.appendGreeting(content);
+    renderGuestbook(req, resp);
+  }
+}
+
diff --git a/appengine/datastore/src/main/java/com/example/appengine/Greeting.java b/appengine/datastore/src/main/java/com/example/appengine/Greeting.java
@@ -0,0 +1,43 @@
+/*
+ * Copyright 2016 Google Inc. All Rights Reserved.
+ *
+ * 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.appengine;
+
+import com.google.appengine.api.datastore.Entity;
+import com.google.appengine.api.users.User;
+import com.google.auto.value.AutoValue;
+import org.joda.time.Instant;
+
+import java.util.Date;
+
+import javax.annotation.Nullable;
+
+@AutoValue
+public abstract class Greeting {
+  static Greeting create(Entity entity) {
+    User user = (User) entity.getProperty("user");
+    Instant date = new Instant((Date) entity.getProperty("date"));
+    String content  = (String) entity.getProperty("content");
+    return new AutoValue_Greeting(user, date, content);
+  }
+
+  @Nullable
+  public abstract User getUser();
+
+  public abstract Instant getDate();
+
+  public abstract String getContent();
+}
diff --git a/appengine/datastore/src/main/java/com/example/appengine/Guestbook.java b/appengine/datastore/src/main/java/com/example/appengine/Guestbook.java
@@ -0,0 +1,66 @@
+/*
+ * Copyright 2016 Google Inc. All Rights Reserved.
+ *
+ * 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.appengine;
+
+import com.example.time.Clock;
+
+import com.google.appengine.api.datastore.DatastoreService;
+import com.google.appengine.api.datastore.Entity;
+import com.google.appengine.api.datastore.FetchOptions;
+import com.google.appengine.api.datastore.Query;
+import com.google.appengine.api.users.User;
+
+import java.util.Date;
+import java.util.List;
+
+/**
+ * A log of notes left by users.
+ *
+ * <p>This demonstrates the use of Google Cloud Datastore using the App Engine
+ * APIs. See the
+ * <a href="https://cloud.google.com/appengine/docs/java/datastore/">documentation</a>
+ * for more information.
+ */
+class Guestbook extends AbstractGuestbook {
+  Guestbook(Clock clock) {
+    super(clock);
+  }
+
+  @Override
+  protected Entity createGreeting(
+      DatastoreService datastore, User user, Date date, String content) {
+    // No parent key specified, so Greeting is a root entity.
+    Entity greeting = new Entity("Greeting");
+    greeting.setProperty("user", user);
+    greeting.setProperty("date", date);
+    greeting.setProperty("content", content);
+
+    datastore.put(greeting);
+    return greeting;
+  }
+
+  @Override
+  protected List<Entity> listGreetingEntities(DatastoreService datastore) {
+    Query query =
+        new Query("Greeting")
+            .addSort("date", Query.SortDirection.DESCENDING);
+    return datastore.prepare(query)
+        .asList(FetchOptions.Builder.withLimit(10));
+  }
+
+
+}