Nashorn in the Future - Speaker Deck

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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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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)

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | Call from Java (2/3) engine.eval("function hello(name){ print('Hello, ' + name); }"); Invocable inv=(Invocable)engine; // Hello, Taro Object obj= inv.invokeFunction("hello","Taro"); 10 Invoke JavaScript function

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | Call from Java (3/3) 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | Replace “const” with “var” • Default: false • It might retire in the future since 8u40 supports const. 14 --const-as-var=true|false

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | Forbid using syntax against ECMAScript standard • Able to use API Extension such as Java.type • Disabled when using -scripting 16 --no-syntax-extensions (-nse)

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | #sourceURL and @sourceURL • For debuging use – //# sourceURL=myScript.js – @sourceURL=myScript.js 17 JDK-8032068 : implement @sourceURL and #sourceURL directives

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | JEP 194: Code Persistence • --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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | JEP 194: Code Persistence • 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | Lazy compilation • Compile methods on demand • Default : true – Before 8u40, default setting was false due to experimental option. 26 --lazy-compilation=true|false

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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”

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | // 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | // 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | Serverside JavaScript... • Node.js compatible framework running on JVM – Nodyn • Vert.x + Dyn.JS + Netty – Trieme • by Apigee • Reactive Programming – RxJS – React.JS 34

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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 ...

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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...

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | Nashorn Project • Nashorn Mailing List – [email protected] • 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/

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 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