Scripting In Java

Scripting in Java
JavaLand 2014
25.03.2014, Lars Gregori

© 2014 Lars Gregori, msgGillardon AG | Scripting in Java | 25.03.2014
Lars Gregori
 msgGillardon AG
 CoC IT-Architekturen
 learn a new language every year
--- The Pragmatic Programmer
3

Was sind Scriptsprachen?
Wikipedia:
„Scriptsprachen sind Programmiersprachen, die vor allem für kleine,
überschaubare Programme gedacht sind. Sie verzichten oft auf
bestimmte Sprachelemente, deren Nutzen erst bei der Bearbeitung
größerer Projekte zum Tragen kommen. So wird etwa in
Skriptsprachen auf den Deklarationszwang von Variablen meist
verzichtet - vorteilhaft zur schnellen Erstellung von kleinen
Programmen (siehe auch Prototyping), bei großen hingegen von
Nachteil, etwa wegen der fehlenden Überprüfungsmöglichkeit von
Tippfehlern in Variablennamen.“
6
http://de.wikipedia.org/wiki/Skriptsprache

Was sind Scriptsprachen?
Wikipedia:
„Scriptsprachen sind Programmiersprachen, die vor allem für kleine,
überschaubare Programme gedacht sind. Sie verzichten oft auf
bestimmte Sprachelemente, deren Nutzen erst bei der Bearbeitung
größerer Projekte zum Tragen kommen. So wird etwa in
Skriptsprachen auf den Deklarationszwang von Variablen meist
verzichtet - vorteilhaft zur schnellen Erstellung von kleinen
Programmen (siehe auch Prototyping), bei großen hingegen von
Nachteil, etwa wegen der fehlenden Überprüfungsmöglichkeit von
Tippfehlern in Variablennamen.“
7
http://de.wikipedia.org/wiki/Skriptsprache

Static vs. Dynamic Typing
 Most scripting languages are dynamically typed
 explicit type declarations not required
 type information is attached to values, not to variables
 Java is static-typed
 require variable type (declaration time)
 only data of declared type
8
https://confluence.deri.ie:8443/display/romulus/Scripting+Languages+and+java

Weak vs. Strong Typing
 Java is a static, strongly typed language
 strongest possible constraint on the type of object at declaration time
 prevents mixing operations between mismatched types
 Many scripting languages are weakly typed
 allow operations on incompatible types
 implicit type conversion or ad-hoc polymorphism
9

Weak vs. Strong Typing
 Java is a static, strongly typed language
 strongest possible constraint on the type of object at declaration time
 prevents mixing operations between mismatched types
 Many scripting languages are weakly typed
 allow operations on incompatible types
 implicit type conversion or ad-hoc polymorphism
10

Quality and Performance
 Scripting languages are more compact and readable
 less lines of code
 weak typing not requiring the overhead of type declaration
 Fewer lines of code and less complexity means lower amounts of
bugs, thus reducing development and maintenance costs.
 The missing type information has some disadvantages.
 static, strongly typed languages ensure the robustness
 type errors will be detected at compile time
11

 runtime performance
 extra overhead of the interpreter and runtime checks
 not performed at compile time
12
http://attractivechaos.github.io/plb/

 runtime performance
 extra overhead of the interpreter and runtime checks
 not performed at compile time
13
http://attractivechaos.github.io/plb/

Motivation

Motivation
 cool
 mal etwas anderes
 macht Spass
 JATUMBA
15

Motivation
 elegant und einfach erweitern
 Konfigurationsdatei
 Datenbank
16

Motivation
 elegant und einfach erweitern
 Konfigurationsdatei
 Datenbank
17

 passender
 Inner DSL
(JRuby)
 String Manipulation
(Jython, Perl)
 map / reduce
(Lisp, Clojure)
 GroovySQL,
GroovyMarkup
 Templates
Motivation
18

 passender
 Inner DSL
(JRuby)
 String Manipulation
(Jython, Perl)
 map / reduce
(Lisp, Clojure)
 GroovySQL,
GroovyMarkup
 Templates
Motivation
19

Motivation
 selbe Technologie
Frontend und Backend
 Javascript Validierung
20

Motivation
 selbe Technologie
Frontend und Backend
 Javascript Validierung
21

Motivation
 langsamer als Java
 Entwickler muss
andere Sprache lernen
22

Motivation
 langsamer als Java
 Entwickler muss
andere Sprache lernen
23

Buch
25
http://www.scriptinginjava.net/
Scripting in Java:
Languages, Frameworks, and Patterns
by Dejan Bosanac
Publisher: Addison Wesley Professional
Pub Date: August 31, 2007 (est.)
Print ISBN-10: 0-321-32193-6
Print ISBN-13: 978-0-321-32193-0
eText ISBN-10: 0-321-50933-1
eText ISBN-13: 978-0-321-50933-8
Pages: 432

Scriptsprachen in Java einbinden
 kompilieren
 eigene Engine
 Bean Scripting Framework (BSF)
 JSR 223 – Scripting for the Java Platform
26

kompilieren – groovyc
27
package my.groovy.jartest
class Answer {
def answer() {
42
}
}
package my.groovy.jartest;
import groovy.lang.GroovyObject;
public class Answer implements GroovyObject
{
...
public Object answer()
{
CallSite[] arrayOfCallSite = $getCallSiteArray();
return Integer.valueOf(42);
return null;
}
}
import my.groovy.jartest;
...
Answer answer = new Answer();
int a = (Integer) answer.answer();

Script Engine
28
GroovyShell gs = new GroovyShell();
String script = "return 42";
int answer = (Integer) gs.evaluate(script);
Binding binding = new Binding();
binding.setVariable("foo", new Integer(2));
GroovyShell shell = new GroovyShell(binding);
Object value = shell.evaluate(
"println 'Hello World!'; x = 123; return foo * 10");
assert value.equals(new Integer(20));
assert binding.getVariable("x").equals(new Integer(123));
http://groovy.codehaus.org/Embedding+Groovy

Bean Scripting Framework (BSF)
 http://commons.apache.org/proper/commons-bsf/
 Bean Scripting Framework (BSF) is a set of Java classes which
provides scripting language support within Java applications, and
access to Java objects and methods from scripting languages.
29

Bean Scripting Framework (BSF) – Beispiel
30
BSFManager manager = new BSFManager();
manager.declareBean("a", 6, Integer.class);
manager.declareBean("b", 7, Integer.class);
String script = "var answer = a * b;" +
"bsf.registerBean("answer", answer)";
manager.eval("javascript", "blah", 0, 0, script);
Double answer = (Double) manager.lookupBean("answer");
assertEquals(42, answer.intValue());

JSR-223 – Scripting for the Java Platform
 The specification describe mechanisms allowing scripting language
programs to access information developed in the Java Platform …
https://jcp.org/en/jsr/detail?id=223
 Java 1.6+
 Rhino JavaScript for Java version 1.6R2
 javax.script.*
 jrunscript
 http://docs.oracle.com/javase/6/docs/technotes/tools/share/jrunscript.html
32

ServiceLoader
 Since: 1.6
 http://docs.oracle.com/javase/6/docs/api/java/util/ServiceLoader.html
 META-INF/services/javax.script.ScriptEngineFactory
 This file contains the single line:
de.torq.clojure.jsr223.ClojureScriptEngineFactory
 Clojure JSR 223 build.xml
 https://github.com/pmf/clojure-jsr223/blob/master/build.xml
33
<jar jarfile="${clojure_jsr223_bundle}" basedir="${build_osgi}">
<service type="javax.script.ScriptEngineFactory“
provider="de.torq.clojure.jsr223.ClojureScriptEngineFactory"/>

JSR-223 – script engines
34

Beispiele
 JRuby
 Groovy
 Clojure
36

JDK 8 – Was ist neu?
 Nashorn
 Lambda
 …
38

Nashorn
 JEP 174
 http://openjdk.java.net/jeps/174
 ECMAScript-262 Edition 5.1
 http://ecma-international.org/ecma-262/5.1/
 javax.script (JSR 223)
40

Nashorn
41

Lambda
 JSR 335
 Lambda Expressions for the Java Programming Language
 https://jcp.org/en/jsr/detail?id=335
 Final Specification
43

invokedynamic
 JavaScript
 4 + 2
 4 + “hallo”
  add(a, b)
46

 http://niklasschlimm.blogspot.de/2012/02/java-7-complete-
invokedynamic-example.html
47

 http://niklasschlimm.blogspot.de/2012/02/java-7-complete-
invokedynamic-example.html
48

Invokedynamic – Jetzt und Zukunft?
 JRuby
 Groovy
 groovy-indy
 Clojure?
50

Bytecode
 Bytecode Frameworks
 ASM : http://asm.ow2.org/
 Javassist : http://www.csg.ci.i.u-tokyo.ac.jp/~chiba/javassist/
 Jitescript : https://github.com/qmx/jitescript
 …
52

Da Vinci Machine
 a multi-language renaissance
for the Java Virtual Machine architecture
 http://openjdk.java.net/projects/mlvm/
 dynamic invocation
 continuations
 tail-calls
 interface injection
55

Credits & making of
 Fotos
 Anja Gregori
 Font
 Chopin Script by ClaudeP
 http://www.dafont.com/chopin-script.font
 Eclipse Plugin
 Bytecode Outline plugin for Eclipse
 http://andrei.gmxhome.de/bytecode/
57

Wir bedanken uns für Ihre Aufmerksamkeit!
msgGillardon AG
Robert-Bürkle-Str. 1
85737 Ismaning
> www.msg-gillardon.de

Range Kata
 http://codingdojo.org/cgi-bin/wiki.pl?KataRange
61
integer range contains
[2,6) contains {2,4}
[2,6) doesn't contain {-1,1,6,10}
getAllPoints?
[2,6) allPoints = {2,3,4,5}
ContainsRange?
[2,5) doesn't contain [7,10)
[2,10) contains [3,5]
[3,5] contains [3,5)
endPoints
[2,6) allPoints = {2,3,4,5}
[2,6] allPoints = {2,3,4,5,6}
(2,6) allPoints = {3,4,5}
(2,6] allPoints = {3,4,5,6}
overlapsRange
[2,5) doesn't overlap with [7,10)
[2,10) overlaps with [3,5)
Equals
[3,5) equals [3,5)
[2,10) neq [3,5)
[2,5) neq [3,10)
[3,5) neq [2,10)

List of freely available programming books
 http://stackoverflow.com/questions/194812/list-of-freely-available-
programming-books/392926#392926
62

JSR 223:
https://code.google.com/p/clojure-jsr223/

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