This post details bytebox, a dependency and runtime to get Java to run on Serverless Architecture via Cloudflare Workers. It uses TeaVM to compile Java into WebAssembly usable by the Cloudflare Workers runtime.
It comes in multiple forms: you can use it as a Gradle plugin to output a deployable worker or a WebAssembly module, and comes as a NPM module to assemble workers by hand. Java dependencies are available via Maven Central and the Gradle Plugin Portal.
An important note about Cloudflare Workers vs Java is that Cloudflare Workers is a single-threaded synchronous state, so all operations are blocking and concurrency is not possible from Java. java.util.concurrent and other threading operations are not included and will result in a compilation error from trying to use them. The GitHub repository lists the full scope of other platform limitations and out-of-scope items, including the use of Process and ProcessBuilder, dynamic class loading, and inbound TCP listening or UDP handlers with DatagramSocket or ServerSocket.
Currently supported are Java 21 and 25 LTS versions. Documentation for both the Java API and the TypeScript API is available at bytebox.gmitch215.dev.
Quick Start
