Crea un'app Java nell'ambiente flessibile di App Engine

Revisione del codice Hello World

Hello World è l'app App Engine più semplice possibile, in quanto contiene un solo servizio, ha una sola versione e tutto il codice si trova nella directory principale dell'app. Questa sezione descrive in dettaglio ciascuno dei file dell'app.

HelloControllerTest.java

Il file HelloControllerTest.java specifica un pattern URL che descrive dove l'app ascolterà le richieste e risponde a qualsiasi richiesta con il messaggio "Hello World".

/*
 * 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

Il file app.yaml descrive la seguente configurazione per la tua app:

• Imposta env: flex, indicando che la tua app utilizza l'ambiente flessibile di App Engine.

• Specifica il runtime utilizzato dall'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

  • Per ulteriori informazioni sul funzionamento dell'ambiente di runtime Java, vedi L'ambiente di runtime Java.

  pom.xml

  Hello World include anche un file pom.xml, che contiene informazioni sul progetto, ad esempio le dipendenze e la destinazione di build.

  <?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>
  

  • Per saperne di più sui file pom.xml, consulta la documentazione di Maven.