In addition to Cloud Functions Framework for Java, the Micronaut framework, Spring Cloud Function project, and Quarkus now have out-of-the-box support for Cloud Functions. You can create both HTTP and background functions using the frameworks' programming models, including capabilities such as dependency injection.
Spring Cloud Functions
You can write a function using Spring Cloud Functions, and deploy it to Java 11 using the Cloud Functions adapter. For details, see the Spring Cloud documentation. Also see the Spring Cloud Functions sample.
You can write a function using Micronaut, and deploy it to Java 11 using Micronaut GCP's Cloud Functions support. For details, see the Micronaut documentation. Also see the Micronaut Cloud Functions sample.