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.
Select your runtime
Cloud Run functions supports several versions of Java, listed on the Supported language runtimes and base images page. You can select the preferred runtime for your function during deployment.
gcloud
To use Cloud Run functions to deploy an HTTP function using the gcloud CLI, see Deploy using the Google Cloud CLI.
Console
If you're using the Google Cloud console, select the runtime when you create and deploy your function. See the Google Cloud console quickstart for detailed instructions.
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.