Slides from my talk, "Server-Side JavaScript with Nashorn" from MidwestJS

1. Server-Side JavaScript
with Nashorn
Dan Woods
@danveloper

2. About Me
Author for InfoQ /danveloper
danielpwoods@gmail.com

3. Intro
My Experiences with PhotoZero!
!
• A client-side file encryption service
!
• Allowed clients to security unlock files/photos with
confidence
!
• Server never knew about the content or password
that a user was uploading, only its chunks in the
position
!
• Salted unlock keys were encrypted to double-down
on security

4. File
Intro
General PhotoZero Overview
Chunks
PZERO
Chunking
Engine
Chunk
Chunk
Chunk
Chunk
Server
Encryptor
Encryptor
Encryptor
Encryptor
DB
Backgrounding: https://github.com/danveloper/jquery-bqep-plugin

5. Intro
PhotoZero & How I came to Server-Side
JavaScript!
!
• Client entirely in HTML5 JavaScript
!
• Decorated with JQuery (some good, mostly bad)
!
• Server-side was implemented on the JVM (Grails)
!
• Non-common language between front-end and
back-end didn’t feel right

6. Intro
Rhino!
!
• Started by Netscape in 1997
!
• Originally designed as Netscape’s (ahem…)
Javagator
!
• Code generation, memory leaks, slow compilation
times

7. Intro
What is Nashorn?!
!
• The Better-than-Rhino JVM JavaScript Engine
!
• Comes out-of-the-box with Java 8 and above
!
• Replacement for Rhino

8. Intro
The Need for Nashorn!
!
• JVM is a polyglot platform
!
• Rhino is old
!
• Comparatively, Rhino is quite slow
!
• ECMAScript compliance

9. Intro
The How of Nashorn!
!
• Truly practical JavaScript on the JVM was not
possible until Java 7
!
• Java 7’s invokeDynamic gives static linking to
dynamic languages (incl. JavaScript)
!
• JVM dynamic languages have runtime support in
method dispatching, without runtime costs

10. Engine Features
Nashorn Features!
!
• 100% ECMAScript 5.1 compliance
!
• Support for a few extensions
• function expression closures - Mozilla 1.8,
• for-each expressions - Mozilla 1.6,
• Rhino constructor extensions
!
• Powerful CLI (jjs) for building command-line scripts!

11. Use Cases
Avatar.js and node.jar!
!
• Avatar is a web framework that brings Node-style
syntax and programming to the JVM
!
• Written by Oracle as a code-gen’d bridge to HTML5
apps
!
• Event-driven support for html web server, SSE
spec, websockets

12. Use Cases
Avatar.js and node.jar!
!
• Respects your Node modules paths, so you can
npm install in the same way
!
• Note: v8 and Nashorn have different ideas about
what the Error class does… I’ve built a “fix”

13. Use Cases
Java Interoperability!
!
• Java has a great modularity story, and its ability to
compose libraries is a huge value to JavaScript
!
• Java has a long history and has figured out
solutions to a lot of the problems of server-side
development
!
• Nashorn’s dynamic linking brings performance with
interoperability; JavaScript methods can be
seamlessly linked and vice-versa

14. Use Cases
What has Java Done Right?!
!
• For better or worse: databases and persistence
!
• Threads; we can’t just ignore these things! They’re
useful!
!
• Right Tool For The Job (tm) — JVM languages
!
• Embedded systems
!
• Build systems (Maven, Gradle, SBT, Ant, etc…)

15. Use Cases
Why Should I Care?!
!
• This platform of interop allows you to use best-of-
breed for the job
!
• Gives you an avenue to refactor existing code to
more sensible JavaScript
!
• Garner all the tooling and monitoring of JMX and
Java instrumentation

16. Use Cases
Server Side Scripting!
!
• Nashorn ships with a script runner (jjs)
!
• Allows server scripts to be written with JavaScript
!
• Special syntax for falling back to shell, and ability to
capture that output (very Perl-like)

17. Use Cases
Performance!
!
• Java 8 introduced practical JavaScript on the JVM
!
• Performance & Compliance is at the forefront, but
the former is still not quite there
!
• The near-term roadmap for the JVM brings
performance enhancements to Nashorn

18. Performance
Performance!
!
• Soon, JavaScript on the JVM will run at near-native
performance levels!
!
• This update will come as part of Java 8u40

19. The Future
The Future…!
!
• Nashorn will make the JVM a platform for
performant dynamic languages, targeting native-
like performance
!
• Java 8 will continue to improve upon JavaScript’s
server-side performance, and will offer other
languages the same performance