Nashorn - The New JavaScript Engine For JVM

Nashorn is a new JavaScript engine written in pure Java. In this session you’ll get introduced to Nashorn and will get answers to the following questions:
- What does it bring to the Java world?
- What capabilities does it provide for the server and the client sides?
- How can you leverage Nashorn in the real-life projects?
You’ll also learn how can we use it today, even before Nashorn is integrated into public JDK8 builds.

Transcript

2. Nashorn The New JavaScript Engine For JVM Anton Moiseev Software Developer, Farata Systems
3. What is Nashorn? ๏ JavaScript Engine for JVM ๏ Ultimate invokedynamic consumer ๏ 100% pure Java implementation ๏ 100% compiled to bytecode, no interpreter ๏ 100% ECMAScript 5.1 compliant
4. Why Nashorn? ๏ Oracle’s motivation: ๏ Validate JSR-292 (invokedynamic) ๏ Reveal performance issues
5. Why Nashorn? ๏ User’s benefits: ๏ Cross-pluggability ๏ Multi-threaded environment ๏ JVM gives: ๏ Multi-platform support ๏ Automatic memory management ๏ Code optimization ๏ Performance ๏ Everyone knows how to write JavaScript ;)
6. Nashorn vs Rhino ๏ Aging ๏ Security issues ๏ Slow ๏ Hard to leverage invokedynamic
7. Performance http://parleys.com/play/5148922b0364bc17fc56c90e/chapter0/about
8. Nashorn vs V8 ๏ No data, but... ๏ Synthetic tests - V8 wins ๏ Typical usage - performance the same
9. JSR-292: invokeDynamic ๏ Since Java 7, greatly improved in Java 8 ๏ For dynamic languages in general ๏ invokeDynamic ≈ function pointer ๏ Everything can be resolved in runtime ๏ Abstracts away bytecode
10. What you can do with Nashorn? ๏ REPL ๏ Shell scripting ๏ Build scripts (ant’s <script> tag) ๏ JavaFX ๏ Server-side (e.g. JavaScript template engines) ๏ Node.jar
11. Features ๏ The only API is JSR-223: javax.scripting.* ๏ Java from JavaScript and vice versa ๏ Create and manipulate Java/JavaScript objects ๏ Extend Java classes ๏ Implement Java interfaces
12. Restrictions ๏ Only ECMA-262 (ECMAScript 5.1) ๏ No typical browser APIs: ๏ HTML5 canvas ๏ HTML5 audio ๏ WebWorkers ๏ WebSockets ๏ WebGL ๏ etc.
13. How to: Java from JS // create instance var list = new java.util.ArrayList(); // package shortcut var util = java.util; var list = new util.ArrayList(); // class shortcut var ArrayList = java.util.ArrayList; var list = new ArrayList(); // using Java.type() var ArrayList = Java.type('java.util.ArrayList'); var list = new ArrayList(); ๏ Object creation:
14. How to: Java from JS var Thread = Java.type('java.lang.Thread'), Runnable = Java.type('java.lang.Runnable'); var thread1 = new Thread(new Runnable({ run: function () { print('Hello from thread1!'); } })); var thread2 = new Thread(new Runnable( function () { print('Hello from thread2!'); } )); var thread3 = new Thread(function () { print('Hello from thread3!'); }); ๏ Interface implementation:
15. How to: Java from JS var MapEntry = java.util.Map.Entry; var MapEntry = Java.type("java.util.Map$Entry"); ๏ Inner classes:
16. How to: JS from Java package jeeconf.demo; import javax.script.*; public class Listing1 { public static void main(String[] args) throws ScriptException { ScriptEngineManager manager = new ScriptEngineManager(); ScriptEngine nashorn = manager.getEngineByName("Nashorn"); nashorn.eval( "function sayHi(){ print('Hey! It\\'s Nashorn!'); } sayHi();" ); } } ๏ Simple invocation:
17. How to: JS from Java package jeeconf.demo; import javax.script.*; public class Listing2 { public static void main(String[] args) throws ScriptException { ScriptEngineManager manager = new ScriptEngineManager(); ScriptEngine nashorn = manager.getEngineByName("Nashorn"); nashorn.eval(            "function  sayHi  (x)  {  print('Hey!  It\\'s  '  +  x  +  '!');  }"        );        Invocable  i  =  (Invocable)  nashorn;        i.invokeFunction("sayHi",  "Nashorn");        i.invokeFunction("sayHi",  "JEEConf"); } } ๏ Passing params and multiple invocation:
18. How to: JS from Java package jeeconf.demo; import javax.script.*; public class Listing2 { public static void main(String[] args) throws ScriptException { ScriptEngineManager manager = new ScriptEngineManager(); ScriptEngine nashorn = manager.getEngineByName("Nashorn"); nashorn.eval( "function sayHi (x) { print('Hey! It\\'s ' + x + '!'); }" + "function run () { sayHi('Nashorn'); }" ); Invocable i = (Invocable) nashorn; Runnable r = i.getInterface(Runnable.class); r.run(); } } ๏ Interface implementation
19. Shell scripting # Using jjs $ jjs ls.js # As executable script (chmod +x ls.js) $ ./ls.js #!/usr/local/bin/jjs -scripting var currentDir = new java.io.File('.'), allFiles = currentDir.list(); for (var i = 0; i < allFiles.length; i ++) { print(allFiles[i]); } ๏ File ls.js: ๏ How to invoke:
20. Build scripts $ ant test Buildfile: /Users/anton/Projects/nashorn/build.xml test: [script] Hey! It's Nashorn! BUILD SUCCESSFUL Total time: 1 second <project> <target name="test"> <script language="nashorn"> <!-- or "javascript" --> print("Hey! It’s Nashorn!"); </script> </target> </project> ๏ File build.xml: ๏ How to invoke:
21. Demo
22. Q & A
23. Contacts Farata Systems: http://faratasystems.com Email: a@antonmoiseev.com Twitter: @antonmoiseev