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Introduction

This repository demonstrates how to use NodeJS/npm modules directly from Java and Kotlin. Why is it useful:

• Gain access to unique JavaScript modules, like the Dat peer to peer file sharing framework shown in the samples.
• Combine your existing NodeJS and Java servers together, eliminating the overheads of REST, serialisation, two separate virtual machines. Simplify your microservices architecture into being a polyglot architecture instead.
• Use it to start porting NodeJS apps to the JVM world and languages, incrementally, one chunk at a time, whilst always having a runnable app. Or do the reverse.

How does it work?

GraalVM is a modified version of OpenJDK that includes the cutting edge Graal and Truffle compiler infrastructure. It provides an advanced JavaScript engine that has competitive performance with V8, and also a modified version of NodeJS 10 that swaps out V8 for this enhanced JVM. In this way you can fuse together NodeJS and the JVM, allowing apps to smoothly access both worlds simultaneously with full JIT compilation.

Known limitations

NodeJS really wants to load module files from the filesystem and nowhere else, so your Java app will need a node_modules directory from where it's started. There are tricks to work around this and allow bundling of JS into JAR files as libraries, but nothing done at the moment.

GraalVM uses NodeJS 10, not the latest versions.

You change java on the command line to nodejvm and that's all it needs, but many tools and IDEs expect the java launcher to always be called java.