JavaOne 2012 CON3978 Scripting Languages on the JVM

© 2012 IBM Corporation

How to embed your scripting languageJavaOne 2012 - CON3978

Paul Thwaite – Java 8 Quality Assurance EngineerMonday 1 October 2012

2 © 2012 IBM Corporation

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Introduction to the speaker – Paul Thwaite

■ 11 years experience developing and deploying Java SDKs

■ Recent work focus:– Quality Assurance specialist

• Leading cross-continent teams• System Test on IBM SDKs

– Quality assurance lead for Java 8• Focus on testing in OpenJDK• OpenJDK contributor

■ My contact information:– [email protected]– linkedin.com/profile/view?id=26327969


What you will learn from this talk

■ Why me and what I do■ Why we run scripting languages on the JVM■ Methods of embedding■ Models of embedding ■ Comparison of two embedding frameworks■ Which approach is best


Why me and what I do

■ Test IBM's Java SDK– I break Java

■ Focus on system testing in QA– Multi-threaded load testing– Third-party applications

■ Increasing use of scripting languages running on the JVM– We need to ensure they run on the IBM SDK


How many languagesrun on the JVM?



>800total

http://en.wikipedia.org/wiki/List_of_JVM_languages

>60active



Most popular include

JavaScript



Why is the JVM so popular?


Why is the JVM so popular?

■ Runtime performance benefits■ Threading and scaling support■ JVM profiling tools■ Access to the impressive array of Java APIs■ Support for multiple languages

The JVM is fast



Let's examine a few implementation methods


Implementation Methods

■ Compiled to bytecodes– Jython– Groovy– Scala




■ Interpreted on the JVM– JavaScript– JRuby




■ Interpreted on the JVM– JavaScript– JRuby

■ Embedded in a Java application on the JVM– Jython– Groovy– Scala– JavaScript– JRuby


Compiled to bytecodes

MyJythonApp

JythoncCompiler

JVM

MyJythonApp.classMyJythonApp.py

Compiling a Jython script to bytecodes and running it on the JVM


Interpreted on the JVM

JRuby.rbJRuby JavaInterpreter

JVM

Interpreting a JRuby script on the JVM

The JRuby language provides the interpreter in Java


Embedding in a Java application

Ruby.rb

Embedding and running a JRuby script inside a Java application on the JVM

MyJavaApp.class JRubyEmbed Engine

JVM

The language provides the embed engine


Embedding in a Java application – multiple scripts

Embedding and running multiple scripts inside a Java application on the JVM


Ruby.rb

Ruby.rb

JRuby.rb

JavaScript.js

MyJavaApp.class

JRubyEmbed Engine

JVM

JavascriptEmbed Engine

JRubyEmbed Engine

JavaScriptEmbed Engine


Scripting on the JVM

Models


Scripting on the JVM - Models

Script Java

JVM

Java Script

JVM

Java Script

JVM


Scripting on the JVM – Script domain knowledge

■ Java objects are created and used from inside the script

■ Requires– Scripting language

knowledge to implement Java objects

– Java knowledge

■ Limited re-use capabilities– Not portable code– Locked in to using the

chosen scripting language

Language-specifc

Script Java

JVM

require 'java'frame = javax.swing.JFrame.new("Window") label = javax.swing.JLabel.new("Hello")frame.getContentPane.add(label)frame.setDefaultCloseOperation (javax.swing.JFrame::EXIT_ON_CLOSE)frame.packframe.setVisible(true)


Scripting on the JVM – Java domain knowledge

■ Java runs a script which is embedded within the Java application

■ The APIs used to invoke the script belong to the scripting language

■ Requires– Java knowledge– Language embed API

knowledge– Bridging knowledge

■ Re-use existing scripts– Optional bridge for

legacy scripts– Investment in using

chosen scripting language

Java Script

JVM

Bridge

import org.jruby.embed.*;ScriptingContainer container = new ScriptingContainer();container.runScriptlet(PathType.RELATIVE, "myscripts/ruby.rb");


Scripting on the JVM – Java and script domain knowledge

■ Options– Invoke a script from a

Java application– Create and use Java

objects inside a script

■ Requires– Java knowledge– Knowledge of the JSR

223 API– Some knowledge of the

scripting language may be required

■ Re-use existing scripts– Support for multiple

scripts

Java Script

JVM

import javax.script.*;ScriptEngineManager engineMgr = new ScriptEngineManager();ScriptEngine engine = engineMgr.getEngineByName("jruby");InputStream is = this.getClass().getResourceAsStream("/myscripts/ruby.rb");Reader reader = new InputStreamReader(is);engine.eval(reader);


What is embedding?


Embedding in a Java application – multiple scripts

Embedding and running multiple scripts inside a Java application on the JVM


Ruby.rb

Ruby.rb

Ruby.rb

JavaScript.js

MyJavaApp.class

JRubyEmbed Engine

JVM

JavascriptEmbed Engine

JRubyEmbed Engine

JavaScriptEmbed Engine


What can you do with an embedded language?

Embedding

Run a script

Call a script's function andretrieve its return valueConfigure script

environment

Pass variables to the script

Run multiple scripts on the

same JVM

Retrieve variables from

the script


Ways to embed a scripting language on the JVM

JSR 223

javax.script

Implementations

Language-specific

Embed

Implementations

● A common API for embedding multiple languages

● Implementation provided by the language

● Some popular languages provide a javax.script API

● Implementation provided by the language

● Similar to JSR223● Extensions available● Ability to fine-tune the scripting

environment● Most popular languages provide

an embed API


Comparison of embedding frameworks

JSR 223

javax.script

Implementations

Language-specific

Embed

Implementationsvs

■ Introduction to javax.script■ Code examples using these languages

– Jruby– Jython– Groovy

■ Exception handling may be missed off some examples to save space


What is javax.script?

■ Allows a developer to embed a scripting language in a Java application ■ Available from Java 6 SE■ Implementation provided by the scripting language■ JSR 223 specification defines 6 interfaces

– ScriptEngine– ScriptEngineFactory– ScriptContext– Bindings– Invocable– Compilable

■ Setup– Download the JSR 223 implementation from your language provider's website– Add the jar(s) to the CLASSPATH– Add your script directory to the CLASSPATH

■ ScriptEngine is discovered at runtime via the JAR services mechanism

JSR 223 Scripting for the Java Platform


Example: Query JAR services for installed JSR223 Java Scripting Engines

import javax.script.*;public class ListScriptEngines {

public static void main(String[] args) {ScriptEngineManager mgr = new ScriptEngineManager();List<ScriptEngineFactory> factories = mgr.getEngineFactories();for (ScriptEngineFactory factory: factories) {

String engName = factory.getEngineName(); String engVersion = factory.getEngineVersion(); System.out.println("Script Engine: " + engName + " V" + engVersion);

} }

}

Output to stdout:Script Engine: Groovy Scripting Engine V2.0Script Engine: jython V2.5.3Script Engine: JSR 223 JRuby Engine V1.6.7.2Script Engine: Mozilla Rhino V1.7 release 3 PRERELEASE

JSR 223


Example: Embedding a Ruby script into a Java application

import javax.script.*;ScriptEngineManager engineMgr = new ScriptEngineManager();ScriptEngine engine = engineMgr.getEngineByName("jruby");InputStream is = this.getClass().getResourceAsStream("/myscripts/ruby.rb");Reader reader = new InputStreamReader(is);engine.eval(reader); //throws ScriptException

Script: /myscripts/ruby.rbstringHello = "Hello, I am a jruby script!"puts "#{stringHello.to_s}"

Output to stdout:Hello, I am a ruby script!"

JSR 223 - JRuby

import org.jruby.embed.*;ScriptingContainer container = new ScriptingContainer();container.runScriptlet(PathType.RELATIVE, "myscripts/ruby.rb");

JRuby Embed API


Example: Passing a variable to a Jython script and retrieving it back again

import javax.script.*;ScriptEngineManager engineMgr = new ScriptEngineManager();ScriptEngine engine = engineMgr.getEngineByName("jython");InputStream is = this.getClass().getResourceAsStream("/myscripts/jython_var.py");Reader reader = new InputStreamReader(is);try {

engine.put("javaString", "red green blue");engine.eval(reader);System.out.println("java> received " + engine.get("javaString"));

} catch (ScriptException e) {}

Script: /myscripts/jython_var.pyprint "jython> received " + javaString javaString += " yellow indigo white"

Output to stdout:jython> received red green bluejava> received red green blue yellow indigo white

JSR 223 - Jython

import org.python.util.PythonInterpreter;PythonInterpreter python = new PythonInterpreter();python.set ( "javaString", new org.python.core.PyString("red green blue"));python.execfile ( "myscripts/jython_var.py" );System.out.println("java> received " + python.get ("javaString"));

Jython Embed API


Example: Invoke a Groovy function with a return value

ScriptEngineManager engineMgr = new ScriptEngineManager();ScriptEngine engine = engineMgr.getEngineByName("groovy");InputStream is = this.getClass().getResourceAsStream("/myscripts/groovy_func.groovy");Reader reader = new InputStreamReader(is);if (engine instanceof Invocable) { //Invocable is an optional interface

Invocable invocableEngine = (Invocable) engine;engine.eval(reader);System.out.println("java> What's the Square root of 360?");double squareRoot = (double) invocableEngine.invokeFunction("squareRoot", 360);System.out.println("java> " + squareRoot);

}

Script: /myscripts/groovy_func.groovydef squareRoot(number) { println "groovy> Sqrt of ${number} is" Math.sqrt(number)}

Output to stdout:java> What's the square root of 360?groovy> Sqrt of 360 isjava> 18.973665961010276

JSR 223 - Groovy

String[] roots = new String[] { "C:\\scripts" };GroovyScriptEngine gse = new GroovyScriptEngine(roots);Class<?> groovyClass = gse.loadScriptByName("groovy_func.groovy");GroovyObject groovyObject = (GroovyObject) groovyClass.newInstance();System.out.println("java> What's the square root of 360?");System.out.println("java> " + groovyObject.invokeMethod("squareRoot", 360).toString());

Groovy Embed API


Example: How to set options in JRuby

// Make JRuby's engine thread safeSystem.setProperty("org.jruby.embed.localcontext.scope", “threadsafe”);

// Turn on JIT verbose loggingSystem.setProperty("jruby.jit.logging.verbose", “true”);

// Set JRuby homeSystem.setProperty("jruby.home", “/path/to/jruby”);

■ JRuby provides many options to the developer to allow for the JRuby ScriptEngine to be customised and finely-tuned

■ In JRuby, these options are set using SystemProperty– Outside the spec of JSR 223– Requires language-specific knowledge


Example: Comparison of setting options in JRuby

■ Jruby's EmbedCore API– Set on a per engine basis– Well documented and easy to find

■ Javax.script API– Set system wide– Multiple engines will all have the same behaviour– Harder to find documentation (not part of an API)

// JRuby EmbedCore API// Make JRuby's engine thread safe// Set via a constructor argument of ScriptingcontainerScriptingContainer instance = new ScriptingContainer(LocalContextScope.THREADSAFE);

// JSR 223 API// Make JRuby's engine thread safeSystem.setProperty("org.jruby.embed.localcontext.scope", “threadsafe”);


Example: Comparison of setting options in Groovy

// Groovy Embed API// Set the compiler warning message levelCompilerConfiguration.setWarningLevel(int warningLevel);

// JSR 223 API// Set the compiler warning message levelNo easy way to do it


How far does javax.script go?

■ Provides useful interaction between Java and many scripting languages– Plug 'n Play support for multiple languages– Great for simple embedding– Easy-to-use API

■ Limitations– The Invocable and Compilable interfaces are optional– Setting language-specific options removes the abstraction JSR 223 provides– Not all engines will provide the same configuration options– Requires knowledge of the underlying ScriptEngine implementation beyond JSR 223


Scripting on the JVM is great

■ Some of the most popular languages support Java embedding■ Embedding a language in a new application is easy to get started■ Deciding how to embed has consequences

–JSR 223 is a great framework for basic embedding

–If you need to harness the power of the language, you will need to use the language API

• For example, JRuby Embed Core

■ How are you embedding your scripting language on the JVM?


References

■ JSR 223– JSR 223 specification

• http://www.jcp.org/en/jsr/detail?id=223

– JRuby implementation• http://kenai.com/projects/jruby/pages/JavaIntegration

– Groovy implementation• http://groovy.codehaus.org/JSR+223+Scripting+with+Groovy

■ Jython Java Integration– http://www.jython.org/jythonbook/en/1.0/JythonAndJavaIntegration.html

■ Scripting in Java: Languages, Frameworks, and Patterns– Dejan Bosanac, Addison-Wesley

http://www.jcp.org/en/jsr/detail?id=223

http://kenai.com/projects/jruby/pages/JavaIntegration

http://groovy.codehaus.org/JSR+223+Scripting+with+Groovy


References

■ Get Products and Technologies:– IBM Java Runtimes and SDKs:

• https://www.ibm.com/developerworks/java/jdk/– IBM Monitoring and Diagnostic Tools for Java:

• https://www.ibm.com/developerworks/java/jdk/tools/

■ Learn:– IBM Java InfoCenter:

• http://publib.boulder.ibm.com/infocenter/java7sdk/v7r0/index.jsp

■ Discuss:– IBM Java Runtimes and SDKs Forum:

• http://www.ibm.com/developerworks/forums/forum.jspa?forumID=367&start=0

https://www.ibm.com/developerworks/java/jdk/

https://www.ibm.com/developerworks/java/jdk/tools/

http://publib.boulder.ibm.com/infocenter/java7sdk/v7r0/index.jsp

http://www.ibm.com/developerworks/forums/forum.jspa?forumID=367&start=0


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JavaOne 2012 CON3978 Scripting Languages on the JVM

Technology

Transcript of JavaOne 2012 CON3978 Scripting Languages on the JVM