Create a Java app in the App Engine flexible environment

Create a Java app in the App Engine flexible environment

Region ID

The REGION_ID is an abbreviated code that Google assigns based on the region you select when you create your app. The code does not correspond to a country or province, even though some region IDs may appear similar to commonly used country and province codes. For apps created after February 2020, REGION_ID.r is included in App Engine URLs. For existing apps created before this date, the region ID is optional in the URL.

Learn more about region IDs.

OK

Note: If you are deploying a new Java web service to Google Cloud, we recommend getting started with Cloud Run.

This quickstart demonstrates how to create and deploy an app that displays a short message. The sample application uses Java version 17.

Before you begin

This quickstart assumes that you have installed the Java SE 17 Development Kit (JDK) on your local machine.

1. Sign in to your Google Cloud account. If you're new to Google Cloud, create an account to evaluate how our products perform in real-world scenarios. New customers also get $300 in free credits to run, test, and deploy workloads.

2. In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

   Note: If you don't plan to keep the resources that you create in this procedure, create a project instead of selecting an existing project. After you finish these steps, you can delete the project, removing all resources associated with the project.

   Go to project selector

3. Make sure that billing is enabled for your Google Cloud project.

4. Enable the Cloud Build API.

   Enable the API

5. Install the Google Cloud CLI.

6. To initialize the gcloud CLI, run the following command:

   gcloud init

7. In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

   Note: If you don't plan to keep the resources that you create in this procedure, create a project instead of selecting an existing project. After you finish these steps, you can delete the project, removing all resources associated with the project.

   Go to project selector

8. Make sure that billing is enabled for your Google Cloud project.

9. Enable the Cloud Build API.

   Enable the API

10. Install the Google Cloud CLI.

11. To initialize the gcloud CLI, run the following command:

    gcloud init

Additional prerequisites

1. Initialize your App Engine app with your project and choose its region:

   gcloud app create --project=[YOUR_PROJECT_ID]
   

   When prompted, select the region where you want to locate your App Engine application.

   Caution: You cannot change an app's region once it has been set.

2. Install the following on your local machine:

   • Download and install Git.
   • Download and install Maven 3.5 or greater. This quickstart uses Apache Maven version 3.5 or greater to build and run the sample app on your computer.

App Engine locations

App Engine is regional, which means the infrastructure that runs your apps is located in a specific region, and Google manages it so that it is available redundantly across all of the zones within that region.

Meeting your latency, availability, or durability requirements are primary factors for selecting the region where your apps are run. You can generally select the region nearest to your app's users, but you should consider the locations where App Engine is available as well as the locations of the other Google Cloud products and services that your app uses. Using services across multiple locations can affect your app's latency as well as its pricing.

You cannot change an app's region after you set it.

Note: Two locations, which are called europe-west and us-central in App Engine commands and in the Google Cloud console, are called europe-west1 and us-central1, respectively, elsewhere in Google documentation.

If you already created an App Engine application, you can view its region by doing one of the following:

• Run the gcloud app describe command.

• Open the App Engine Dashboard in the Google Cloud console. The region appears near the top of the page.

OK

Download the Hello World app

We've created a Hello World app for App Engine so you can quickly get a feel for deploying an app to the Google Cloud.

1. Clone the Hello World sample app repository to your local machine.

   git clone https://github.com/GoogleCloudPlatform/java-docs-samples
   

   Alternatively, you can download the sample as a zip file and extract it.

2. Change to the directory that contains the sample code.

      cd java-docs-samples/flexible/java-17/micronaut-helloworld
   

Run Hello World on your local machine

To run the Hello World app on your local computer:

1. Run the following command:

   java -jar target/micronaut-helloworld-0.1.jar

2. In your web browser, enter the following address:

   http://localhost:8080

   If you are using Cloud Shell, in the toolbar, click Web Preview and select Preview on port 8080 instead.

The Hello World message from the sample app displays on the page. In your terminal window, press Ctrl+C to exit the web server.

Deploy and run Hello World on App Engine

To deploy your app to the App Engine flexible environment:

1. Deploy the Hello World app by running the following command from the java-17/micronaut-helloworld directory:

   mvn clean package appengine:deploy

2. Launch your browser to view the app at https://PROJECT_ID.REGION_ID.r.appspot.com

   gcloud app browse

   where PROJECT_ID represents your Google Cloud project ID.

This time, the page that displays the Hello World message is delivered by a web server running on an App Engine instance.

Congratulations! You've deployed your first App Engine app to the App Engine flexible environment!

If you encountered any errors deploying your application, check the troubleshooting tips.

See the following sections for information about cleaning up as well as links to possible next steps that you can take.

Clean up

To avoid incurring charges, you can delete your Google Cloud project to stop billing for all the resources used within that project.

Caution: Deleting a project has the following effects:
• Everything in the project is deleted. If you used an existing project for the tasks in this document, when you delete it, you also delete any other work you've done in the project.
• Custom project IDs are lost. When you created this project, you might have created a custom project ID that you want to use in the future. To preserve the URLs that use the project ID, such as an appspot.com URL, delete selected resources inside the project instead of deleting the whole project.
1. In the Google Cloud console, go to the Manage resources page.

   Go to Manage resources

2. In the project list, select the project that you want to delete, and then click Delete.
3. In the dialog, type the project ID, and then click Shut down to delete the project.

What's next

Learn the whole platform

Now that you know what it's like to develop and deploy App Engine apps, you can explore the rest of Google Cloud. You already have the Google Cloud CLI installed which gives you the tools to interact with products like Cloud SQL, Cloud Storage, Firestore, and more.

Learn about the App Engine flexible environment

Here are some topics to help continue your learning about App Engine:

• An overview of App Engine
• Request routing
• Request handling
• Managing instances

Hello World code review

Hello World is the simplest possible App Engine app, as it contains only one service, has only one version, and all of the code is located within the app's root directory. This section describes each of the app files in detail.

HelloControllerTest.java

The HelloControllerTest.java file specifies a URL pattern that describes where the app will listen for requests, and responds to any requests with the 'Hello World' message.

/*
 * Copyright 2023 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
 *
 * 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 static org.junit.Assert.assertEquals;

import io.micronaut.context.ApplicationContext;
import io.micronaut.http.HttpRequest;
import io.micronaut.http.client.HttpClient;
import io.micronaut.runtime.server.EmbeddedServer;
import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.Test;

public class HelloControllerTest {
  private static EmbeddedServer server;
  private static HttpClient client;

  @BeforeClass
  public static void setupServer() {

    server = ApplicationContext.run(EmbeddedServer.class);

    client = server.getApplicationContext().createBean(HttpClient.class, server.getURL());
  }

  @AfterClass
  public static void stopServer() {
    if (client != null) {
      client.stop();
    }
    if (server != null) {
      server.stop();
    }
  }

  @Test
  public void testHelloWorldResponse() {
    String response = client.toBlocking().retrieve(HttpRequest.GET("/"));
    assertEquals("Hello World!", response);
  }
}

app.yaml

The app.yaml file describes the following configuration for your app:

• Sets env: flex, indicating your app uses the App Engine flexible environment.

• Specifies the runtime used by the app.

  runtime: java
  env: flex
  runtime_config:
    operating_system: ubuntu22
    runtime_version: 17
  handlers:
  - url: /.*
    script: this field is required, but ignored
  
  manual_scaling:
    instances: 1

  • For more information on how the Java runtime works, see The Java runtime.

  pom.xml

  Hello World also includes a pom.xml file, which contains information about the project, such as its dependencies and the build target.

  <?xml version="1.0" encoding="UTF-8"?>
  <!--
    Copyright 2023 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
         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 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.appengine.flexible</groupId>
    <artifactId>micronaut-helloworld</artifactId>
    <version>0.1</version>
  
    <!--
    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>
      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <exec.mainClass>com.example.appengine.Application</exec.mainClass>
      <maven.compiler.target>11</maven.compiler.target>
      <maven.compiler.source>11</maven.compiler.source>
      <micronaut.version>3.10.3</micronaut.version>
    </properties>
  
    <dependencies>
      <dependency>
        <groupId>io.micronaut</groupId>
        <artifactId>micronaut-inject</artifactId>
        <version>${micronaut.version}</version>
        <scope>compile</scope>
      </dependency>
      <dependency>
        <groupId>io.micronaut</groupId>
        <artifactId>micronaut-validation</artifactId>
        <version>${micronaut.version}</version>
        <scope>compile</scope>
      </dependency>
      <dependency>
        <groupId>io.micronaut</groupId>
        <artifactId>micronaut-runtime</artifactId>
        <version>${micronaut.version}</version>
        <scope>compile</scope>
      </dependency>
      <dependency>
        <groupId>io.micronaut</groupId>
        <artifactId>micronaut-http-client</artifactId>
        <version>${micronaut.version}</version>
        <scope>compile</scope>
      </dependency>
      <dependency>
        <groupId>javax.annotation</groupId>
        <artifactId>javax.annotation-api</artifactId>
        <version>1.3.2</version>
        <scope>compile</scope>
      </dependency>
      <dependency>
        <groupId>io.micronaut</groupId>
        <artifactId>micronaut-http-server-netty</artifactId>
        <version>${micronaut.version}</version>
        <scope>compile</scope>
      </dependency>
      <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.13.2</version>
        <scope>test</scope>
      </dependency>
    </dependencies>
  
    <build>
      <plugins>
        <plugin>
          <groupId>com.google.cloud.tools</groupId>
          <artifactId>appengine-maven-plugin</artifactId>
          <version>2.8.0</version>
          <configuration>
            <projectId>GCLOUD_CONFIG</projectId>
            <version>micronaut-helloworld</version>
          </configuration>
        </plugin>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-shade-plugin</artifactId>
          <version>3.5.1</version>
          <executions>
            <execution>
              <phase>package</phase>
              <goals>
                <goal>shade</goal>
              </goals>
              <configuration>
                <transformers>
                  <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                    <mainClass>${exec.mainClass}</mainClass>
                  </transformer>
                  <transformer implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"/>
                </transformers>
              </configuration>
            </execution>
          </executions>
        </plugin>
        <plugin>
          <groupId>org.codehaus.mojo</groupId>
          <artifactId>exec-maven-plugin</artifactId>
          <version>3.1.1</version>
          <configuration>
            <executable>java</executable>
            <arguments>
              <argument>-noverify</argument>
              <argument>-XX:TieredStopAtLevel=1</argument>
              <argument>-Dcom.sun.management.jmxremote</argument>
              <argument>-classpath</argument>
              <classpath/>
              <argument>${exec.mainClass}</argument>
            </arguments>
          </configuration>
        </plugin>
        <plugin>
          <artifactId>maven-surefire-plugin</artifactId>
          <version>3.2.5</version>
        </plugin>
  
          <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.12.1</version>
            <configuration>
              <encoding>UTF-8</encoding>
              <compilerArgs>
                <arg>-parameters</arg>
              </compilerArgs>
              <annotationProcessorPaths>
                <path>
                  <groupId>io.micronaut</groupId>
                  <artifactId>micronaut-inject-java</artifactId>
                  <version>${micronaut.version}</version>
                </path>
                <path>
                  <groupId>io.micronaut</groupId>
                  <artifactId>micronaut-validation</artifactId>
                  <version>${micronaut.version}</version>
                </path>
              </annotationProcessorPaths>
            </configuration>
            <executions>
              <execution>
                <id>test-compile</id>
                <goals>
                  <goal>testCompile</goal>
                </goals>
                <configuration>
                  <compilerArgs>
                    <arg>-parameters</arg>
                  </compilerArgs>
                  <annotationProcessorPaths>
                    <path>
                      <groupId>io.micronaut</groupId>
                      <artifactId>micronaut-inject-java</artifactId>
                      <version>${micronaut.version}</version>
                    </path>
                    <path>
                      <groupId>io.micronaut</groupId>
                      <artifactId>micronaut-validation</artifactId>
                      <version>${micronaut.version}</version>
                    </path>
                  </annotationProcessorPaths>
                </configuration>
              </execution>
            </executions>
          </plugin>
        </plugins>
  
    </build>
  </project>
  

  • For more information about pom.xml files, see the Maven documentation.