The Java runtime

Your Cloud Run function runs in an environment consisting of an operating system version with add-on packages, language support, and the Java Functions Framework library that supports and invokes your function. This environment is identified by the language version, and is known as the runtime ID.

Function preparation

You can prepare a function directly from the Google Cloud console or write it on your local machine and upload it. To prepare your local machine for Java development, see Set up a Java development environment.

Supported Java runtimes and base images

Runtime Runtime ID Stacks Runtime base image
Java 21 java21
  • google-22 (default)
  • google-22-full
    		•
  • google-22/java21
  • google-22-full/java21
    		•
    Java 17 java17
  • google-22 (default)
  • google-22-full
    		•
  • google-22/java17
  • google-22-full/java17
    		•
    Java 11 java11 google-18-full google-18-full/java11

    Select your runtime

    You can select one of the supported Java runtimes for your function during deployment.

    You can select a runtime version using the Google Cloud console, or the gcloud CLI. Click the tab for instructions on using the tool of your choice:

    gcloud

    Specify the Java base image for your function using the --base-image flag, while deploying your function. For example:

    gcloud run deploy FUNCTION \
    --source . \
    --function FUNCTION_ENTRYPOINT \
    --base-image java21

    Replace:

    • FUNCTION with the name of the function you are deploying. You can omit this parameter entirely, but you will be prompted for the name if you omit it.

    • FUNCTION_ENTRYPOINT with the entry point to your function in your source code. This is the code Cloud Run executes when your function runs. The value of this flag must be a function name or fully-qualified class name that exists in your source code.

    For detailed instructions on deploying a function using the gcloud CLI, see Deploy functions in Cloud Run.

    Console

    You can select a runtime version when you create or update a Cloud Run function in the Google Cloud console. For detailed instructions on deploying a function, see Deploy functions in Cloud Run.

    To select a runtime in the Google Cloud console when you create a function, follow these steps:

    1. In the Google Cloud console, go to the Cloud Run page:

      Go to Cloud Run

    2. Click Write a function.

    3. In the Runtime list, select a Java runtime version.

    4. Click Create, and wait for Cloud Run to create the service using a placeholder revision.

    5. The console will redirect you to the Source tab where you can see the source code of your function. Click Save and redeploy.

    For detailed instructions on updating the runtime version after your function is deployed, see Re-deploy new source code.

    Source code structure

    For Cloud Run functions to find your function's definition, your source code must follow a specific structure. See Write Cloud Run functions for more information.

    Specifying dependencies

    You can specify dependencies for your function using Maven or Gradle. For more information, see Specify dependencies in Java.

    Environment variables

    Your Java runtime automatically sets certain environment variables for your function to use as needed. For details, see Configure environment variables.

    Execution ID

    For Java functions that use functions-framework version 1.4.0 or later, you can use the logging class java.util.logging.Logger to add a unique execution ID to log outputs. Using stdout or stderr (for example, System.println()) does not add the execution ID.

    Note that:

    • If you created your function using the Cloud Functions v2 API (for example, by using gcloud functions, the REST API, or Terraform), this execution ID is added automatically.

    • If you created your function using the Cloud Run Admin API (for example, by using Google Cloud console, gcloud run, the REST API, or Terraform), you need to set the LOG_EXECUTION_ID environment variable to true to use this feature.