Create and deploy an HTTP Cloud Run function by using Java (1st gen)

This guide takes you through the process of writing a Cloud Run function using the Java runtime. There are two types of Cloud Run functions:

  • An HTTP function, which you invoke from standard HTTP requests.
  • An event-driven function, which you use to handle events from your Cloud infrastructure, such as messages on a Pub/Sub topic, or changes in a Cloud Storage bucket.

The document shows how to create a simple HTTP function and build it using either Maven or Gradle.

Before you begin

  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.

    Roles required to select or create a project

    • Select a project: Selecting a project doesn't require a specific IAM role—you can select any project that you've been granted a role on.
    • Create a project: To create a project, you need the Project Creator role (roles/resourcemanager.projectCreator), which contains the resourcemanager.projects.create permission. Learn how to grant roles.

    Go to project selector

  3. Verify that billing is enabled for your Google Cloud project.

  4. Enable the Cloud Functions and Cloud Build APIs.

    Roles required to enable APIs

    To enable APIs, you need the Service Usage Admin IAM role (roles/serviceusage.serviceUsageAdmin), which contains the serviceusage.services.enable permission. Learn how to grant roles.

    Enable the APIs

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

    Roles required to select or create a project

    • Select a project: Selecting a project doesn't require a specific IAM role—you can select any project that you've been granted a role on.
    • Create a project: To create a project, you need the Project Creator role (roles/resourcemanager.projectCreator), which contains the resourcemanager.projects.create permission. Learn how to grant roles.

    Go to project selector

  6. Verify that billing is enabled for your Google Cloud project.

  7. Enable the Cloud Functions and Cloud Build APIs.

    Roles required to enable APIs

    To enable APIs, you need the Service Usage Admin IAM role (roles/serviceusage.serviceUsageAdmin), which contains the serviceusage.services.enable permission. Learn how to grant roles.

    Enable the APIs

    8.
  8. Install and initialize the Google Cloud SDK.
  9. Update and install gcloud components: 
    gcloud components update
  10. Prepare your development environment.

    Go to the Java setup guide

Create a function

This section describes how to create a function.

Maven

  1. Create a directory on your local system for the function code:

    Linux or Mac OS X:

     mkdir ~/helloworld  cd ~/helloworld

    Windows:

     mkdir %HOMEPATH%\helloworld  cd %HOMEPATH%\helloworld

  2. Create the project structure to contain the source directory and source file.

    mkdir -p src/main/java/functions touch src/main/java/functions/HelloWorld.java

  3. Add the following contents to the HelloWorld.java file:

     package functions; import com.google.cloud.functions.HttpFunction; import com.google.cloud.functions.HttpRequest; import com.google.cloud.functions.HttpResponse; import java.io.BufferedWriter; import java.io.IOException; public class HelloWorld implements HttpFunction {  // Simple function to return "Hello World"  @Override  public void service(HttpRequest request, HttpResponse response)  throws IOException {  BufferedWriter writer = response.getWriter();  writer.write("Hello World!");  } }

    This example function outputs the greeting "Hello World!"

Gradle

  1. Create a directory on your local system for the function code:

    Linux or Mac OS X:

     mkdir ~/helloworld-gradle  cd ~/helloworld-gradle

    Windows:

     mkdir %HOMEPATH%\helloworld-gradle  cd %HOMEPATH%\helloworld-gradle

  2. Create the project structure to contain the source directory and source file.

     mkdir -p src/main/java/functions  touch src/main/java/functions/HelloWorld.java

  3. Add the following contents to the HelloWorld.java file:

     package functions; import com.google.cloud.functions.HttpFunction; import com.google.cloud.functions.HttpRequest; import com.google.cloud.functions.HttpResponse; import java.io.BufferedWriter; import java.io.IOException; public class HelloWorld implements HttpFunction {  // Simple function to return "Hello World"  @Override  public void service(HttpRequest request, HttpResponse response)  throws IOException {  BufferedWriter writer = response.getWriter();  writer.write("Hello World!");  } }

    This example function outputs the greeting "Hello World!"

Specify dependencies

The next step is to set up dependencies:

Maven

Change directory to the helloworld directory you created above, and create a pom.xml file:

 cd ~/helloworld  touch pom.xml

To manage dependencies using Maven, specify the dependencies in the <dependencies> section inside the pom.xml file of your project. For this exercise, copy the following contents into your pom.xml file.

<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.functions</groupId>  <artifactId>functions-hello-world</artifactId>  <version>1.0.0-SNAPSHOT</version>  <properties>  <maven.compiler.target>11</maven.compiler.target>  <maven.compiler.source>11</maven.compiler.source>  </properties>  <dependencies>  <!-- Required for Function primitives -->  <dependency>  <groupId>com.google.cloud.functions</groupId>  <artifactId>functions-framework-api</artifactId>  <version>1.1.0</version>  <scope>provided</scope>  </dependency>  </dependencies>  <build>  <plugins>  <plugin>  <!--  Google Cloud Functions Framework Maven plugin  This plugin allows you to run Cloud Functions Java code  locally. Use the following terminal command to run a  given function locally:  mvn function:run -Drun.functionTarget=your.package.yourFunction  -->  <groupId>com.google.cloud.functions</groupId>  <artifactId>function-maven-plugin</artifactId>  <version>0.11.0</version>  <configuration>  <functionTarget>functions.HelloWorld</functionTarget>  </configuration>  </plugin>  </plugins>  </build> </project>

See helloworld for a complete sample based on Maven.

Gradle

Change directory to the helloworld-gradle directory you created above, and create a build.gradle file:

 cd ~/helloworld-gradle  touch build.gradle

To manage dependencies using Gradle, specify the dependencies in the build.gradle file of your project. For this exercise, copy the following contents into your build.gradle file. Note that this build.gradle file includes a custom task to help you run functions locally.

apply plugin: 'java' repositories {  jcenter()  mavenCentral() } configurations {  invoker } dependencies {  // Every function needs this dependency to get the Functions Framework API.  compileOnly 'com.google.cloud.functions:functions-framework-api:1.1.0'  // To run function locally using Functions Framework's local invoker  invoker 'com.google.cloud.functions.invoker:java-function-invoker:1.3.1'  // These dependencies are only used by the tests.  testImplementation 'com.google.cloud.functions:functions-framework-api:1.1.0'  testImplementation 'junit:junit:4.13.2'  testImplementation 'com.google.truth:truth:1.4.0'  testImplementation 'org.mockito:mockito-core:5.10.0' } // Register a "runFunction" task to run the function locally tasks.register("runFunction", JavaExec) {  main = 'com.google.cloud.functions.invoker.runner.Invoker'  classpath(configurations.invoker)  inputs.files(configurations.runtimeClasspath, sourceSets.main.output)  args(  '--target', project.findProperty('run.functionTarget') ?: '',  '--port', project.findProperty('run.port') ?: 8080  )  doFirst {  args('--classpath', files(configurations.runtimeClasspath, sourceSets.main.output).asPath)  } }

See helloworld-gradle for a complete sample based on Gradle.

Build and test locally

Before deploying the function, you can build and test it locally:

Maven

Run the following command to confirm that your function builds:

mvn compile

Another option is to use the mvn package command to compile your Java code, run any tests, and package the code up in a JAR file within the target directory. You can learn more about the Maven build lifecycle here.

To test the function, run the following command:

mvn function:run

Gradle

Run the following command to confirm that your function builds:

gradle build

To test the function, run the following command:

gradle runFunction -Prun.functionTarget=functions.HelloWorld

If testing completes successfully, it displays the URL you can visit in your web browser to see the function in action: http://localhost:8080/. You should see a Hello World! message.

Alternatively, you can send requests to this function using curl from another terminal window:

curl localhost:8080 # Output: Hello World!

Deploy the function

Maven

To deploy the function with an HTTP trigger, run the following command in the helloworld directory: 

gcloud functions deploy my-first-function --no-gen2 --entry-point functions.HelloWorld --runtime java17 --trigger-http --memory 512MB --allow-unauthenticated
 where my-first-function is the registered name by which your function will be identified in the Google Cloud console, and --entry-point specifies your function's fully qualified class name (FQN).

Gradle

To deploy the function with an HTTP trigger, run the following command in the helloworld-gradle directory: 

gcloud functions deploy my-first-function --no-gen2 --entry-point functions.HelloWorld --runtime java17 --trigger-http --memory 512MB --allow-unauthenticated
 where my-first-function is the registered name by which your function will be identified in the Google Cloud console, and --entry-point specifies your function's fully qualified class name (FQN).

Test the deployed function

  1. When the function finishes deploying, take note of the httpsTrigger.url property or find it using the following command: 

    gcloud functions describe my-first-function
     It should look like this:

    https://GCP_REGION-PROJECT_ID.cloudfunctions.net/my-first-function

  2. Visit this URL in your browser. You should see a Hello World! message.

View logs

Logs for Cloud Run functions are viewable using the Google Cloud CLI, and in the Cloud Logging UI.

Use the command-line tool

To view logs for your function with the gcloud CLI, use the logs read command, followed by the name of the function:

gcloud functions logs read my-first-function

The output should resemble the following:

LEVEL NAME EXECUTION_ID TIME_UTC LOG D my-first-function k2bqgroszo4u 2020-07-24 18:18:01.791 Function execution started D my-first-function k2bqgroszo4u 2020-07-24 18:18:01.958 Function execution took 168 ms, finished with status code: 200 ...

Use the Logging dashboard

You can also view logs for Cloud Run functions from the Google Cloud console.