docs(sample): Add sample for native image support in Firestore

samples/native-image-sample/README.md

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+# Firestore Sample Application with Native Image
+
+This application uses the [Google Cloud Firestore client libraries](https://cloud.google.com/firestore/docs/quickstart-servers#java) and is compatible with Native Image compilation.
+
+This sample runs through basic operations of creating a new document, running queries, and then deleting the created resources.
+
+## Setup Instructions
+
+You will need to follow these prerequisite steps in order to run the samples:
+
+1. If you have not already, [create a Google Cloud Platform Project](https://cloud.google.com/resource-manager/docs/creating-managing-projects#creating_a_project).
+
+2. Install the [Google Cloud SDK](https://cloud.google.com/sdk/) which will allow you to run the sample with your project's credentials.
+
+   Once installed, log in with Application Default Credentials using the following command:
+
+    ```
+    gcloud auth application-default login
+    ```
+
+   **Note:** Authenticating with Application Default Credentials is convenient to use during development, but we recommend [alternate methods of authentication](https://cloud.google.com/docs/authentication/production) during production use.
+
+3. Install the GraalVM compiler.
+
+   You can follow the [official installation instructions](https://www.graalvm.org/docs/getting-started/#install-graalvm) from the GraalVM website.
+   After following the instructions, ensure that you install the native image extension installed by running:
+
+    ```
+    gu install native-image
+    ```
+
+   Once you finish following the instructions, verify that the default version of Java is set to the GraalVM version by running `java -version` in a terminal.
+
+   You will see something similar to the below output:
+
+    ```
+    $ java -version
+
+    openjdk version "11.0.7" 2020-04-14
+    OpenJDK Runtime Environment GraalVM CE 20.1.0 (build 11.0.7+10-jvmci-20.1-b02)
+    OpenJDK 64-Bit Server VM GraalVM CE 20.1.0 (build 11.0.7+10-jvmci-20.1-b02, mixed mode, sharing)
+    ```
+
+## Sample
+
+1. If you wish to run the application against the [Firestore emulator](https://cloud.google.com/sdk/gcloud/reference/beta/emulators/firestore), make sure that you have the [Google Cloud SDK](https://cloud.google.com/sdk) installed.
+
+   In a new terminal window, start the emulator via `gcloud`:
+
+    ```
+    gcloud beta emulators firestore start --host-port=localhost:9010
+    ```
+
+   Leave the emulator running in this terminal for now.
+   In the next section, we will run the sample application against the Firestore emulator instance.
+
+
+2. Navigate to this directory and compile the application with the Native Image compiler.
+
+    ```
+    mvn package -P native -DskipTests
+    ```
+
+3. **(Optional)** If you're using the emulator, export the `FIRESTORE_EMULATOR_HOST` as an environment variable in your terminal.
+
+    ```
+    export FIRESTORE_EMULATOR_HOST=localhost:9010
+    ``` 
+
+   The Firestore Client Libraries will detect this environment variable and automatically connect to the emulator instance if this variable is set.
+
+4. Run the application.
+
+    ```
+    ./target/native-image-sample
+    ```
+
+5. The application will run through some basic Firestore operations and log some output statements.
+
+    ```
+    Created user alovelace. Timestamp: 2020-12-15T20:19:28.444070000Z
+    The following users were saved:
+    Document: alovelace | Ada Lovelace born 1815
+    Number of users born before 1900: 1
+    Number of users born earlier after 1900: 0
+    Number of users whose first name is 'Ada': 0
+    ```
+
+## Sample Integration test with Native Image Support
+
+In order to run the sample integration test as a native image, call the following command:
+
+   ```
+   mvn test -Pnative
+   ```

samples/native-image-sample/pom.xml

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+<?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.example.firestore</groupId>
+  <artifactId>native-image-sample</artifactId>
+  <name>Native Image Sample</name>
+  <url>https://github.com/googleapis/java-firestore</url>
+
+  <!--
+    The parent pom defines common style checks and testing strategies for our samples.
+    Removing or replacing it should not affect the execution of the samples in anyway.
+  -->
+  <parent>
+    <groupId>com.google.cloud.samples</groupId>
+    <artifactId>shared-configuration</artifactId>
+    <version>1.2.0</version>
+  </parent>
+
+  <properties>
+    <maven.compiler.target>11</maven.compiler.target>
+    <maven.compiler.source>11</maven.compiler.source>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+  </properties>
+
+  <dependencyManagement>
+    <dependencies>
+      <dependency>
+        <groupId>com.google.cloud</groupId>
+        <artifactId>libraries-bom</artifactId>
+        <version>24.2.0</version>
+        <type>pom</type>
+        <scope>import</scope>
+      </dependency>
+    </dependencies>
+  </dependencyManagement>
+
+  <dependencies>
+    <dependency>
+      <groupId>com.google.cloud</groupId>
+      <artifactId>google-cloud-firestore</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <version>4.13.2</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>com.google.truth</groupId>
+      <artifactId>truth</artifactId>
+      <version>1.1.3</version>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-jar-plugin</artifactId>
+        <configuration>
+          <archive>
+            <manifest>
+              <mainClass>com.example.firestore.NativeImageFirestoreSample
+              </mainClass>
+            </manifest>
+          </archive>
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
+
+  <!-- Native Profile-->
+  <profiles>
+    <profile>
+      <id>native</id>
+
+      <dependencies>
+        <dependency>
+          <groupId>com.google.cloud</groupId>
+          <artifactId>native-image-support</artifactId>
+          <version>0.10.0</version>
+        </dependency>
+        <dependency>
+          <groupId>org.junit.vintage</groupId>
+          <artifactId>junit-vintage-engine</artifactId>
+          <version>5.8.2</version>
+          <scope>test</scope>
+        </dependency>
+        <dependency>
+          <groupId>org.graalvm.buildtools</groupId>
+          <artifactId>junit-platform-native</artifactId>
+          <version>0.9.9</version>
+          <scope>test</scope>
+        </dependency>
+      </dependencies>
+
+      <build>
+        <plugins>
+          <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-surefire-plugin
+            </artifactId> <!-- Must use older version of surefire plugin for native-image testing. -->
+            <version>2.22.2</version>
+            <configuration>
+              <includes>
+                <include>**/IT*</include>
+              </includes>
+            </configuration>
+          </plugin>
+          <plugin>
+            <groupId>org.graalvm.buildtools</groupId>
+            <artifactId>native-maven-plugin</artifactId>
+            <version>0.9.9</version>
+            <extensions>true</extensions>
+            <configuration>
+              <mainClass>com.example.firestore.NativeImageFirestoreSample
+              </mainClass>
+              <buildArgs>
+                <buildArg>--no-fallback</buildArg>
+                <buildArg>--no-server</buildArg>
+              </buildArgs>
+            </configuration>
+            <executions>
+              <execution>
+                <id>build-native</id>
+                <goals>
+                  <goal>build</goal>
+                  <goal>test</goal>
+                </goals>
+                <phase>package</phase>
+              </execution>
+              <execution>
+                <id>test-native</id>
+                <goals>
+                  <goal>test</goal>
+                </goals>
+                <phase>test</phase>
+              </execution>
+            </executions>
+          </plugin>
+        </plugins>
+      </build>
+    </profile>
+  </profiles>
+</project>

samples/native-image-sample/src/main/java/com/example/firestore/NativeImageFirestoreSample.java

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+/*
+ * Copyright 2020-2021 Google LLC
+ *
+ * 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
+ *
+ *     https://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.firestore;
+
+import com.google.api.core.ApiFuture;
+import com.google.cloud.firestore.CollectionReference;
+import com.google.cloud.firestore.DocumentReference;
+import com.google.cloud.firestore.FieldPath;
+import com.google.cloud.firestore.Firestore;
+import com.google.cloud.firestore.FirestoreOptions;
+import com.google.cloud.firestore.Query;
+import com.google.cloud.firestore.QueryDocumentSnapshot;
+import com.google.cloud.firestore.QuerySnapshot;
+import com.google.cloud.firestore.WriteResult;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Sample Firestore application demonstrating basic operations.
+ */
+public class NativeImageFirestoreSample {
+
+  private static final String USERS_COLLECTION = "nativeimage_test_users";
+
+  /**
+   * Entrypoint to the Firestore sample application.
+   */
+  public static void main(String[] args) throws Exception {
+    Instant startTime = Instant.now();
+    FirestoreOptions firestoreOptions = FirestoreOptions.getDefaultInstance();
+    Firestore db = firestoreOptions.getService();
+
+    deleteCollection(db);
+    createUserDocument(db);
+    createUserDocumentPojo(db);
+    readDocuments(db);
+    runSampleQueries(db);
+    Instant endTime = Instant.now();
+    Duration duration = Duration.between(startTime, endTime);
+    System.out.println("Duration: " + duration.toString());
+  }
+
+  static void deleteCollection(Firestore db) throws Exception {
+    Iterable<DocumentReference> documents = db.collection(USERS_COLLECTION).listDocuments();
+    for (DocumentReference doc : documents) {
+      doc.delete().get();
+    }
+  }
+
+  static void createUserDocument(Firestore db) throws Exception {
+    DocumentReference docRef = db.collection(USERS_COLLECTION).document("alovelace");
+    Map<String, Object> data = new HashMap<>();
+    data.put("id", "10");
+    data.put("first", "Ada");
+    data.put("last", "Lovelace");
+    data.put("born", 1815);
+
+    WriteResult result = docRef.set(data).get();
+    System.out.println("Created user " + docRef.getId() + ". Timestamp: " + result.getUpdateTime());
+  }
+
+  static void createUserDocumentPojo(Firestore db) throws Exception {
+    CollectionReference collectionReference = db.collection(USERS_COLLECTION);
+    WriteResult result =
+        collectionReference.document()
+            .set(new Person("Alan", "Turing", 1912))
+            .get();
+
+    System.out.println("Created user by POJO. Timestamp: " + result.getUpdateTime());
+  }
+
+  static void readDocuments(Firestore db) throws Exception {
+    ApiFuture<QuerySnapshot> query = db.collection(USERS_COLLECTION).get();
+    QuerySnapshot querySnapshot = query.get();
+    List<QueryDocumentSnapshot> documents = querySnapshot.getDocuments();
+    System.out.println("The following users were saved:");
+    printUsers(documents);
+  }
+
+  static void runSampleQueries(Firestore db) throws Exception {
+    List<QueryDocumentSnapshot> results =
+        runQuery(db.collection(USERS_COLLECTION).whereLessThan("born", 1900));
+    System.out.println("Number of users born before 1900: " + results.size());
+
+    results = runQuery(
+        db.collection(USERS_COLLECTION).whereGreaterThan(FieldPath.of("born"), 1900));
+    System.out.println("Number of users born earlier after 1900: " + results.size());
+
+    results = runQuery(
+        db.collection(USERS_COLLECTION).whereEqualTo("name", "Ada"));
+    System.out.println("Number of users whose first name is 'Ada': " + results.size());
+  }
+
+  private static List<QueryDocumentSnapshot> runQuery(Query query) throws Exception {
+    QuerySnapshot querySnapshot = query.get().get();
+    List<QueryDocumentSnapshot> documents = querySnapshot.getDocuments();
+    return documents;
+  }
+
+  private static void printUsers(Iterable<QueryDocumentSnapshot> documents) {
+    for (QueryDocumentSnapshot document : documents) {
+      System.out.printf(
+          "Document: %s | %s %s born %d\n",
+          document.getId(),
+          document.getString("first"),
+          document.getString("last"),
+          document.getLong("born"));
+    }
+  }
+}