Nashorn in the future (English)

Nashorn in the Future
Oracle Corporation Japan
Fusion Middleware Business Unit
NISHIKAWA, Akihiro
8, April, 2015
Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |

Safe Harbor Statement
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.
2

Agenda
What's Nashorn?
8u20
8u40
In the future...
1
2
3
4
3

What’s Nashorn?
4

Nashorn
• Replacement for Rhino
– For improving security and performance
• Proof of Concept for InvokeDynamic (JSR-292)
5
JavaScript Engine introduced in Java 8 (JEP 174)

Nashorn
• ECMAScript-262 Edition 5.1
• javax.script (JSR 223) API
• Interaction between Java and JavaScript
• Command line tool : jjs
JavaScript Engine introduced in Java 8 (JEP 174)
6

Get started!
• jjs
– Hello World
– Lambda Expression, Stream
• Scripting
– User the option of “-scripting”
– Call Web API
• JavaFX
– User the option of “–fx”
– WebView
7

Lambda Expression in Nashorn
// Java
array.stream().sorted(Comparator.naturalOrder())
.forEach( t -> sortedArray.add(t) );
// Nashorn
array.stream().sorted(Comparator.naturalOrder())
.forEach(function(t) sortedArray.add(t));
8

Call from Java (1/3)
ScriptEngineManager manager =
new ScriptEngineManager();
ScriptEngine engine =
manager.getEngineByName("nashorn");
// Evaluation
engine.eval("print('hello world')"); // hello world
engine.eval(new FileReader(“hello.js”)); // hello.js
9

engine.eval("function hello(name){
print('Hello, ' + name); }");
Invocable inv=(Invocable)engine;
// Hello, Taro
Object obj= inv.invokeFunction("hello","Taro");
10
Invoke JavaScript 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();
11
Implement interface with Script function

8u20
12

8u20
• Focused on security improvement and enhancement of underlying
platform
– JIT
– JDK
13
Released in August, 2014

Replace “const” with “var”
• Default: false
• It might retire in the future since 8u40 supports const.
14
--const-as-var=true|false

Forbid access Java Packages and Classes from JavaScript
• Default : false
15
--no-java=true|false (-nj)

Forbid using syntax against ECMAScript standard
• Able to use API Extension such as Java.type
• Disabled when using -scripting
16
--no-syntax-extensions (-nse)

#sourceURL and @sourceURL
• For debuging use
– //# sourceURL=myScript.js
– @sourceURL=myScript.js
17
JDK-8032068 : implement @sourceURL and #sourceURL directives

Class Cache
• Originally compilation is required even if invoking previous used script.
• Since 8u20, previous evaluated script is stored in cache for reuse.
• Example
– from Java
engine.eval(new URLReader(myScriptURL));
– from JavaScript
load(url);
18
JDK-8021350 : Share script classes between threads/globals within context

8u40
19

8u40
• Performance improvement
– Optimistic typing (JEP 196)
– Code Persistence (JEP 194)
• Security
– Class Filter (JEP 202)
• Partial support for ECMAScript 6
– Lexical-scoped variables and constant definition (JEP 203)
20
Implemented JEP

JEP 196: Optimistic Typing
• Type inference at compilation (not at runtime)
– Assume specific type used at operation
and manipulation of array index
– If type inference is wrong, fall back and
recompile with more pessimistic assumption
• --optimistic-types=true|false (-ot)
– Default: false
21
For generating bytecode like Java
int long
double
Object

JEP 196: Optimistic Typing
• nashorn.typeInfo.maxFiles
– Maximum # of files to cache type information
– if 0 is set to this property, caching is disabled.
• nashorn.typeInfo.cacheDir
– Directory where files storing cached type information exist.
• Windows: ${java.io.tmpdir}¥com.oracle.java.NashornTypeInfo
• Linux and Solaris: ~/.cache/com.oracle.java.NashornTypeInfo
• Mac OS X: ~/Library/Caches/com.oracle.java.NashornTypeInfo
22
Caching result of type inference

JEP 194: Code Persistence
• Cache code for re-use within the same process.
• This helps smaller memory usage and shorter startup time.
23
Performance improvement with caching code

• --class-cache-size=50 (-ccs)
– Class cache size per global scope
– Default : 50
• --persistent-code-cache=true|false (-pcc)
– Specifies whether or not optimistic type information as well as compiled scripts are
persisted to disk
– Default : false
24
Performance improvement with caching code

• Where is code cache stored?
– Default : When invoking JavaScript, directory named nashorn_code_cache is
created and cached data are stored.
– Directory name is configurable.
• nashorn.persistent.code.cache
• File stored cached data contains not only class byte code but also various
metadata.
25
Optimistic type information is also cached to disk

Lazy compilation
• Compile methods on demand
• Default : true
– Before 8u40, default setting was false due to experimental option.
26
--lazy-compilation=true|false

JEP 202: Class Filter
• JEP 202: Nashorn Class Filter
https://bugs.openjdk.java.net/browse/JDK-8043717
• Impementation is required in Java application which uses JavaScript.
– jdk.nashorn.api.scripting.ClassFilter
27
Forbid accessing Java classes from JavaScript

ClassFilter
// restrcting access to java.io.File
import jdk.nashorn.api.scripting.ClassFilter;
class MyFilter implements ClassFilter {
@Override
public boolean exposeToScripts(String s) {
if (s.compareTo("java.io.File") == 0) return false;
return true;
}
}
28
Implementation example

Partial support for ECMAScript 6
29

JEP 203: Lexically-scoped variable and constant declarations
• --language=es5|es6
– Default : es5
– --language=es6 is mandatory when using const and let
30
Support for keyword “let” and “const”

// let
let a=2;
function f(x) {
// a=2
if(x) {
let a=42;
}
// a is still equal to 2
}
// var
var a=2;
function f(x) {
// a is not undefined
if(x) {
var a=42;
}
// depending upon x, a is
equal to 42 or undefined
}
31
let and var

// 1) Syntax error
function f(x) {
const b=1;
// Unable to assign
b = 99;
}
// 2) Scope #1
function f(x) {
const b=1;
var z=b+1; //z=2
}
//b is undefined
var y=b+1;
32
// 3) Scope #2
function f(x) {
const b=1;
var z =b+1; //z=2
}
//Able to declare b
const b = 10;
const

Server Side JavaScript
33

Serverside JavaScript...
• Node.js compatible framework running on JVM
– Nodyn
• Vert.x + Dyn.JS + Netty
– Trieme
• by Apigee
• Reactive Programming
– RxJS
– React.JS
34

In the future...
36

In the Future
• Improve with steady work
– Shorter warmup time
– Enhancement/improvement of Optimistic Typing and Code Persistence
• Java 9
– Fully suport for ECMAScript 6 (Java 9)
– Parser API for Nashorn (JEP 236)
– Java Flight Recorder
• JavaScript Profiler
• Tag for Nashorn
...etc
37
Java 8u60, 9, and ...

Improve with steady work
• Improve performance when parsing JSON
– Poor performance when handling small JSON objects using
PropertyHashMap#findElement
• Re-write jdk.nashorn.internal.parser.JSONParser
38
For example...

Java Flight Recorder
39

JEP 236: Parser API for Nashorn
• Objective
– Parser API for representing ECMAScript code as AST
– Visitor pattern
– Introduced to hide internal implementation package (jdk.nashorn.internal.ir)
• Notice
– Not script level API but Java API
40
Public API for ECMAScript AST

JEP 236: Parser API for Nashorn
• Available after JDK9 b55
• JavaDoc
– https://bugs.openjdk.java.net/br
owse/JDK-8048176
41
jdk.nashorn.api.tree

Takeaway
42

Key takeaway
• Many features and improvement
have been introduced to 8u20
and 8u40.
• Nashorn is being improved day
by day, of course.
• Please give your feedback to
development team!
43

Nashorn Project
• Nashorn Mailing List
– nashorn-dev@openjdk.java.net
• Nashorn Wiki
– https://wiki.openjdk.java.net/display/Nashorn/Main
• DEVELOPER_README
– http://hg.openjdk.java.net/jdk8u/jdk8u-
dev/nashorn/file/tip/docs/DEVELOPER_README
• Nashorn - JavaScript for the JVM
– http://blogs.oracle.com/nashorn/
44
http://openjdk.java.net/projects/nashorn/

Safe Harbor Statement
The preceding 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.
45

Nashorn in the future (English)

Nashorn in the future (English)

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