Spring Cloud Function is a project with the following high-level goals:

  • Promote the implementation of business logic via functions.

  • Decouple the development lifecycle of business logic from any specific runtime target so that the same code can run as a web endpoint, a stream processor, or a task.

  • Support a uniform programming model across serverless providers, as well as the ability to run standalone (locally or in a PaaS).

  • Enable Spring Boot features (auto-configuration, dependency injection, metrics) on serverless providers.

It abstracts away all of the transport details and infrastructure, allowing the developer to keep all the familiar tools and processes, and focus firmly on business logic.

Here’s a complete, executable, testable Spring Boot application (implementing a simple string manipulation):

public class Application {

  public Function<String, String> uppercase() {
    return value -> value.toUpperCase();

  public static void main(String[] args) {, args);

It’s just a Spring Boot application, so it can be built, run and tested, locally and in a CI build, the same way as any other Spring Boot application. The Function is from java.util and Flux is a Reactive Streams Publisher from Project Reactor. The function can be accessed over HTTP or messaging.

Spring Cloud Function has the following features:

  • Choice of programming styles - reactive, imperative or hybrid.

  • Function composition and adaptation (e.g., composing imperative functions with reactive).

  • Support for reactive function with multiple inputs and outputs allowing merging, joining and other complex streaming operation to be handled by functions.

  • Transparent type conversion of inputs and outputs.

  • Packaging functions for deployments, specific to the target platform (e.g., Project Riff, AWS Lambda and more)

  • Adapters to expose function to the outside world as HTTP endpoints etc.

  • Deploying a JAR file containing such an application context with an isolated classloader, so that you can pack them together in a single JVM.

  • Adapters for AWS Lambda, Azure, Google Cloud Functions, and possibly other "serverless" service providers.