Nashorn: JavaScript Running on Java VM (English)

Copyright © 2014, Oracle and/or its affiliates. All rights reserved.1
JavaScript Running On
JavaVM: Nashorn
NISHIKAWA, Akihiro
Oracle Corporation Japan

The following is intended to outline our general product direction. It
is intended for information purposes only, and may not be
incorporated into any contract.
It is not a commitment to deliver any material, code, or functionality,
and should not be relied upon in making purchasing decisions. The
development, release, and timing of any features or functionality
described for Oracle’s products remains at the sole discretion of
Oracle.

Copyright © 2014, Oracle and/or its affiliates. All rights reserved.3 Copyright © 2013, Oracle and/or its affiliates. All rights reserved.
Agenda  Nashorn
 Server Side JavaScript
 Nashorn in the future

Nashorn

Nashorn
JavaScript Engine running on Java VM

Backgrounds
 Replacing Rhino
– Concerns about security, performance, and so on
 Proof of Concept for InvokeDynamic (JSR-292)
 Atwood's law
Any application that can be written in JavaScript will
eventually be written in JavaScript.

Scope of Project Nashorn
JEP 174
 ECMAScript-262 Edition 5.1 compliant
 Support for javax.script (JSR 223) API
 Interaction between Java and JavaScript
 Newly introduced command line tool (jjs)

Java VM
Scripting Engine
(Nashorn)
Scripting API
(JSR-223)
JavaScript codeJava code
Other runtime
Other APIs jjs

$JAVA_HOME/bin/jjs
$JAVA_HOME/jre/lib/ext/nashorn.jar

ECMAScript-262 Edition 5.1 compliant

Out of scope of Project Nashorn
 ECMAScript 6 (Harmony)
– Generators
– Destructuring assignment
– const, let, ...
 DOM/CSS and related libraries
– jQuery, Prototype, Dojo, …
 Browser API and browser emulator
– HTML5 canvas, HTML5 audio, WebGL, WebWorkers...

Examples

Invoke Nashorn from Java
ScriptEngineManager manager
= new ScriptEngineManager();
ScriptEngine engine
= manager.getEngineByName("nashorn");
engine.eval("print('hello world')");
engine.eval(new FileReader("hello.js"));

Invoke script function from Java
engine.eval("function hello(name) {
print('Hello, ' + name)}");
Invocable inv=(Invocable)engine;
Object obj=
inv.invokeFunction("hello","Taro");

Implement an interface with script function
engine.eval("function run(){
print('run() called’)
}");
Invocable inv =(Invocable)engine;
Runnable r=inv.getInterface(Runnable.class);
Thread th=new Threads(r);
th.start();
th.join();

Invoke Java/JavaFX from Nashorn
print(java.lang.System.currentTimeMillis());
jjs -fx ...

Nashorn for Scripting
Additional feature for scripting use
 -scripting option
 Here document
 Back quote
 String Interpolation
...

Nashorn Extensions

Nashorn Extensions
The following topics are covered in this session.
 How to get references of Java type
 How to access properties of Java objects
 Relationship among Lambda, SAM, and Script function
 Scope and context

Java type

How to get references of Java type
Expression in Rhino (This expression is valid in Nashorn)
var hashmap=new java.util.HashMap();
Or
var HashMap=java.util.HashMap;
var hashmap=new HashMap();

How to get references of Java type
Recommended expression in Nashorn
var HashMap=Java.type('java.util.HashMap');
var hashmap=new HashMap();

Java.type
Class or Package?
java.util.ArrayList
java.util.Arraylist

Java Array
Expression in Rhino
var intArray=
java.lang.reflect.Array.newInstance(
java.lang.Integer.TYPE, 5);
var Array=java.lang.reflect.Array;
var intClass=java.lang.Integer.TYPE;
var array=Array.newInstance(intClass, 5);

Java Array
Expression in Nashorn
var intArray=new(Java.type("int[]"))(5);
var intArrayType=Java.type("int[]");
var intArray=new intArrayType(5);

Access properties of
Java objects

Using getter and setter
var map=new HashMap();
map.put('size', 2);
print(map.get('size')); // 2

Directly
map.size=3;
print(map.size); // 3
print(map.size()); // 1

Using Associative Array
map['size']=4;
print(map['size']); // 4
print(map['size']()); // 1

Lambda, SAM,
and Script function

Lambda, SAM, and Script function
Nashorn converts a script function to a lambda object or any SAM
interface implementing object automatically.
var timer=new java.util.Timer();
timer.schedule(
function() { print('Tick') }, 0, 1000);
java.lang.Thread.sleep(5000);
timer.cancel();

Lambda, SAM, and Script function
Any Java object which is an instance of lambda type can be treated like a
script function.
var JFunction=
Java.type('java.util.function.Function');
var obj=new JFunction() {
// x->print(x*x)
apply: function(x) { print(x*x) }
}
print(typeof obj); //function
obj(9); // 81 like Script function

Scope and Context

Scope and Context
load and loadWithNewGlobal
 load
– Load scripts in the same global scope.
– If same name variables are in the original scripts and
loaded scripts, Corruption of each variable may happen.
 loadWithNewGlobal
– Load scripts in another global scope newly created.
– Even if same name variables are in the original scripts
and loaded scripts, Corruption of each variable may not
happen.

Scope and Context
ScriptContext contains one or more Bindings each associated each jsr223
"scope".
ScriptContext ctx=new SimpleScriptContext();
ctx.setBindings(engine.createBindings(),
ScriptContext.ENGINE_SCOPE);
Bindings engineScope=
ctx.getBindings(ScriptContext.ENGINE_SCOPE);
engineScope.put("x", "world");
engine.eval("print(x)", ctx);

Scope and Context
Using with clause and JavaImporter
with(new JavaImporter(java.util, java.io)){
var map=new HashMap(); //java.util.HashMap
map.put("js", "javascript");
map.put("java", "java");
print(map);
....
}

Others
 Convert between Java array and JavaScript array
– Java.from
– Java.to
 Extend Java class and access super-class
– Java.extend
– Java.super
and so on...

Server Side JavaScript

Java EE for Next Generation Applications
Deliver HTML5, Dynamic and Scalable Applications
WebSockets
Avatar

Evolution of Web application architecture
Request-Response and Multi-page application
Java EE/JVM
Presentation
(Servlet/JSP)
Business
Logic
Backend
ConnectivityBrowser

Evolution of Web application architecture
Use Ajax (JavaScript)
Java EE/JVM
Connectivity
(REST, SSE)
Presentation
(Servlet/JSP, JSF)
Business
Logic
Backend
ConnectivityBrowser
JavaScript

Modern Web application architecture
Rather connectivity than Presentation – Single Page Application
Java EE/JVM
Connectivity
(WebSocket,
REST, SSE)
Presentation
(Servlet/JSP, JSF)
Business
Logic
Backend
ConnectivityBrowser
View
Controller
JavaScript

How about Node.js?

Mobile-enabled existing services with Node.js
Node.js
JavaScript
REST
SSE
WebSocket
Browser
View
Controller
JavaScript

How about
Node.js on JVM?

Mobile-enabled existing services with Node
Node running on Java VM
Java EE/JVM
Node
Server
Business
Logic
Backend
Connectivity
Client
JavaScriptBrowser
View
Controller
JavaScript

Avatar.js

Avatar.js
Old name is "node.jar"
 Able to use almost all of modules available on Node.js
– Express, async, socket.io, ...
 Some modules are required to modify.
– Automatically recognize modules downloaded with
npm.
 Pros.
– Leverage node programming model
– Leverage existing Java assets, knowledge, and tools

Avatar.js = Node + Java
Leverage Java technologies including Threads
JavaJavaScript
com.myOrg.myObj
java.util.SortedSet
java.lang.Thread
require('async')
postEvent
Node App

Avatar

Avatar
Server side JavaScript services framework
 Provide data transmission features via REST, WebSocket,
and Server Sent Event (SSE)
 Leverage event-driven programming model and
programming modules of Node.js
 Integrate with Enterprise Features (Java EE)

*.html
*.js
*.css
HTTP
Application
Services
Avatar Modules
Node Modules
Avatar.js
Avatar Runtime
Avatar Compiler
Server Runtime (Java EE)
JDK 8 / Nashorn
Application
Views
REST/WebSocket/SSE
Avatar (Avatar EE)
Change
Notification
Data

HTTP
REST/WebSocket/SSE
Avatar Compiler
Application
Views
*.html
*.js
*.css
Application
Services
Avatar Modules
Node Modules
Avatar.js
Avatar Runtime
JDK 8 / Nashorn
Architecture (Server Side)
Change
Notification
Data

Avatar Service
Java
JavaScript
HTTP Load Balancer
Services
Shared State
Services Services
Change
Notification
Data

Avatar Runtime
Avatar Modules
Node Modules
Avatar.js
*.html
*.js
*.css
Application
Services
JDK 8 / Nashorn
Architecture (Client Side)
Change
Notification
Data
HTTP
REST/WebSocket/SSE
Application
Views
Avatar Compiler

Avatar and Avatar.js
progress steadily.

Nashorn in the future

Nashorn in the future
 Bytecode Persistence (JEP 194)
http://openjdk.java.net/jeps/194
 Optimistic Typing
 Others

Summary

Key takeaways
 Nashorn
– Tightly integrated with Java
– Pay attention to different expression when migrating
artifacts from Rhino to Nashorn
– Progress steadily (performance improvement, new
features, compliant against new standards)
 Server Side JavaScript
– Avatar.js and Avatar are on-going.
– Please feedback!

Appendix

Source code walk through
Shell jjs uses mainly.
Compiler generates classes (bytecode) from sources.
Scanner Create tokens from sources.
Parser Create AST/IR from tokens.
IR Elements of scripts
Codegen Create script class bytecode from AST/IR
Objects Runtime elements (Object, String, Number, Date, RegExp)
Scripts Classes including codes for scripts
Runtime Runtime tasks
Linker Binds callees on runtime based on JSR-292 (InvokeDynamic)
Dynalink Searching for best methods (available across languages)

Nashorn Documents
http://wiki.openjdk.java.net/display/Nashorn/Nashorn+Documentation
 Java Platform, Standard Edition Nashorn User's Guide
http://docs.oracle.com/javase/8/docs/technotes/guides/scripting/nash
orn/
 Scripting for the Java Platform
http://docs.oracle.com/javase/8/docs/technotes/guides/scripting/
 Oracle Java Platform, Standard Edition Java Scripting Programmer's
Guide
http://docs.oracle.com/javase/8/docs/technotes/guides/scripting/prog_
guide/

Nashorn
http://openjdk.java.net/projects/nashorn/
 OpenJDK wiki – Nashorn
https://wiki.openjdk.java.net/display/Nashorn/Main
 Mailing List
nashorn-dev@openjdk.java.net
 Blogs
– Nashorn - JavaScript for the JVM
http://blogs.oracle.com/nashorn/
– Nashorn Japan
https://blogs.oracle.com/nashorn_ja/

Avatar.js
 Project Page
https://avatar-js.java.net/
 Mailing List
users@avatar-js.java.net

Avatar
 Project Page
https://avatar.java.net/
 Mailing List
users@avatar.java.net

Nashorn: JavaScript Running on Java VM (English)

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