JavaScript Evented I/O & more
for the Java Enterprise Ecosystem

Niko Köbler (@dasniko)
{JavaScript}Training

Node.js on the JVM

What is Node.js?

• Server-side JavaScript platform built on Google V8 engine
• What JavaScript has done for the webbrowser,
  Node.js is doing for the backend server
• http://nodejs.org

• Asyncronous, non-blocking, evented I/O with JavaScript

The Event Loop

The cost of I/O

L1-cache              3 cycles
L2-cache             14 cycles
RAM                 250 cycles
Disk         41 000 000 cycles
Network     240 000 000 cycles

Why JavaScript?

Why Java?

With Java, we have...

And now, you wanna tell us
about this "brave" new (Node-)JS-world?

Speaking JavaScript

http://speakingjs.com

Node.js Advisory Board - October 23, 2014

Atwood's Law

http://blog.codinghorror.com/the-principle-of-least-power/

Integration

Integration

Integration

invoke

Nashorn

• JavaScript Enginge on the JVM
• based on invokedynamic feature
• competes with Google V8
• ECMAScript 5.1 compatible (ES6/ES2015 with Java 9)
• Seamless interoperability of Java and JavaScript
• Shell Scripting
• Language and API Extensions

http://openjdk.java.net/projects/nashorn/​

closures, collections & for each, multi-line string literals, string interpolation, __noSuchProperty__, __noSuchMethod__, typed arrays, binding properties, error extensions, conditional catch clause, String functions, and many, many more...

Java and JavaScript

...are similar than car and carpet are similar.

Nashorn

Command Line Client

$ $JAVA_HOME/bin/jjs
jjs> print('Hello Nashorn!');

Nashorn

Invoking JavaScript from Java

ScriptEngine engine = new ScriptEngineManager()
                              .getEngineByName("nashorn");
engine.eval("print('Hello Nashorn!');");

engine.eval(new FileReader("scriptfile.js"));

Invocable invocable = (Invocable) engine;
Object result = invocable.invokeFunction(
                              "jsSayHello", "Nashorn");

Nashorn

Invoking Java from JavaScript

package my.package;
public class MyJavaClass {
    static String sayHello(String name) {
        return String.format("Hello %s from Java!", name);
    }
}

var MyJavaClass = Java.type('my.package.MyJavaClass');
var result = MyJavaClass.sayHello('Nashorn');
print(result); // Hello Nashorn from Java!

Nashorn

Listing Docker Containers via REST-Call from Shell

#!/usr/bin/jjs -fv
var host = "DOCKER_HOST"
var dockerUri="http://${host}:5555/containers/json";
var command = "curl ${dockerUri}";
$EXEC(command);
var containers = JSON.parse($OUT);
for each(container in containers){
    print("${container.Image} / 
           ${container.Names[0]} / 
           ${container.Status}");
}

(by Adam Bien)

Avatar

The Oracle solution

Avatar 2.0

• Inter-thread communication

  • Message Bus

  • Shared State (Map API: Key-Value-Store)

• Model-Store-API

  • JPA (Eclipselink) / JDBC based

• https://avatar.java.net  /  https://avatar-js.java.net

Avatar 2.0

by project:odd @RedHat

http://nodyn.io

• http://dynjs.org
• also based on invokedynamic
• REPL / command line
• Java interaction / embedding

http://netty.io

Netty

Node.js Architecture

Nodyn Architecture

• http://vertx.io
• Polyglott*
• Simplicity
• Scalability
• Concurrency
• Distributed Event Bus**

*) Java, JavaScript, Ruby, Groovy, Python, Scala, Clojure, Ceylon

**) using Hazelcast In-Memory Data Grid (hazelcast.org)

vertx2-core

This module exposes the vert.x 2.x eventbus to node.js clients.

https://github.com/nodyn/vertx2-core

mod-nodyn

This supports running Node.js workloads inside of Vert.x.

https://github.com/nodyn/mod-nodyn

var http = require("http");
var vertx = require("vertx2-core");

var registration = vertx.eventbus.register("bar", function(message) {
  var amount = message.body.amount;
  console.log("BAR: Someone ordered " + amount + " beer(s).");
  message.reply({wait_time: amount * 1.75});
});

var server = http.createServer(function(request, response) {
  var parts = request.url.split("/");
  var amount = parts[1];

  vertx.eventbus.send("bar", {amount: amount}, function(message) {
    response.write(amount + " beer(s) will be ready in "
        + message.body.wait_time + " minutes");
    response.end();
  });
});

server.listen(9000, function() {
  console.log( "Beer-Server is listening on port 9000" );
});

beer-as-a-service.js

run with nodyn

var http = require("http");
var vertx = require("vertx2-core");

var server = http.createServer(function(request, response) {
  var parts = request.url.split("/");
  var amount = parts[1];

  vertx.eventbus.send("bar", {amount: amount}, function(message) {
    response.write(amount + " beer(s) will be ready in "
        + message.body.wait_time + " minutes");
    response.end();
  });
});

server.listen(9000, function() {
  console.log( "Beer-Server is listening on port 9000" );
});

beer-web.js

beer-bar.js

var eventBus = require("vertx/event_bus");

eventBus.registerHandler("bar", function(message, replier) {
  java.lang.System.err.println("BAR: Someone ordered " + message.amount + " beer(s)");
  replier({wait_time: message.amount * 1.75});
});

java.lang.System.err.println("The BAR is open!");

run with vertx in cluster mode