Introduction to JRubMe

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Introduction to JRubME

Roy Ben HayunEngineering ServicesCSG

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Sun Confidential: Internal Only 2

Topics• Requirements for mobile Ruby• Port of the native Ruby VM (MRI)• Porting JRuby to Java ME

> CLDC> CDC

• More things to do..


Requirements for mobile Ruby


Possible usages for mobile Ruby• Simple application development• Prototyping• Development tools• Education• Not Ruby on Rails.

• Not much usage today. • Possibly in few years when/if scripting languages

gain more traction in mobile space


Requirements from JRubyME• What do we actually want to get?

> The power of Ruby language> JRuby's Java bindings > An acceptable working subset

• What can we keep for later?> Ruby to JVM bytecode compilation > Threading> Any advanced feature


Port of the native Ruby VM (MRI)


Porting the native Ruby MRI• See

http://developer.symbian.com/main/tools/opensrc/ruby• Native porting effort is lengthy• Need to port per OS • Requires additional effort for API access

> Mobile APIs> GUI

• MRI port gives only barebones Ruby language > No mobile APIs


Comparing native MRI vs JRuby port• Porting involved:

> Hybrid of C, K&R C, Symbian C++ vs Java only

• Porting time:> Weeks vs Days

• Value achieved in those ports:> Interpreter – approximately same in both> No OS APIs vs Java APIs via JRuby Java binding> Required customization vs platform independent> JRubME is easier to extend and enhance


Porting JRuby to Java ME


Choosing the Java ME plaform• CLDC based solution

> The current Java ME de-facto standard> MIDP provides rich mobile APIs> Requires build-time modifications to replace reflection> Requires source modifications to JRuby

• CDC based solution> e.g., Sony Ericsson P990, M600> Closer to a desktop Java environment> Requires source modifications to JRuby


Choosing the JRuby baseline• Newer versions (v0.9.8 from 2007)

> Closer to the main JRuby branch for easy integration> Has more advanced features

• Taking an older version (v0.8.2 from 2006)> Has less advanced features> Minimize the porting effort to get a working subset

– Less code, fewer dependencies, fewer libraries> Provides the interpreter and Java bindings

– Which is what we need for now


Various options for JRuby on Java ME• Newer JRuby mainlines (X axis)

> More language and VM features> Better Maintainability

• Java platform power (Y axis)> Less porting effort> More usability

/ JRuby 0.9.8CLDC

/ JRuby 0.8.2CLDC

/ JRuby 0.9.8CDC

/ JRuby 0.8.2CDC

Java platform closer to desktop

Newer JRuby mainlines

trade-off line

Effort

Usability

Maintainability

features


JRuby 0.9.8 on CLDC• Initial exploration to get some hands-on feeling• Minor obstacles

> Missing classes/packages (i.e. collections, nio, regex)> Missing methods in existing classes> Migrating to GCF> Obstacles accumulate

/ JRuby 0.9.8CLDC


JRuby 0.9.8 on CLDC main obstacles• Obstacles accumulate

• Java bindings require reflection capability• Possible solutions:

> Pseudo reflection mechanism> Hard wired code support for specific classes

– LCDUI, PIM, connectivity, persistance etc.> Same process as using the C API for the native Ruby

VM


Usability obstacle on CLDC• Sandboxing limits the usage of JRuby on mobiles

> Limits usage to MIDP APIs> Can not jump out of the sandbox> Limits options of development tools

– i.e. Limits dynamic extensions of testing frameworks


Summary of obstacles on CLDC • CLDC porting effort becomes a handcrafted port

> Although, it’s not a full rewrite> But big enough to diverge from the mainline JRuby

• Need to have a CLDC version.

• A more powerful JRuby on CDC should come first> Provide a proof of concept > Prototype for mobile usage> Attract developers


Porting process to CDC• Avoid “We don’t need all that!”• Avoid the big bang blind port

• Decremental iterations to downgrade JRuby mainline and platform> Ensure it is running on Java SE 1.X> Regress down to Java SE 1.X-1

• Move to CDC> And tell the world!

• Incremental iterative steps > Integrate with newer JRuby mainlines> Migrate to CLDC

/ JRuby 0.9.8CLDC

/ JRuby 0.8.2CLDC

/ JRuby 0.9.8CDC

/ JRuby 0.8.2CDC


Regress on Java SE 1.4• Ensuring it runs on Java SE 1.5 and 1.4

• Less libraries to remove then newer JRuby mainlines> junit.jar> bsf.jar and javasupport.bsf.*> ant.jar and the AST serialization

• Remove asserts• No java.nio.*• (No autoboxing in the source..)


Regress on Java SE 1.3• Chained exceptions

• Few more minor removals> Missing methods i.e. String.split(), Boolean.valueOf()> Missing classes i.e. StackTraceElement> Restricted access i.e. java.util.Calendar.setTimeInMills()


Regress on Java SE 1.3• Bigger obstacle is that there is no java.util.regex.*• Solution

> Find a replacement package e.g.,Java 1.4> Paste into a new package jrubyme.poc.[package]> Modifications as required to package and client code

– e.g., sun.text.Normalizer silently commented out.

• And do the same for other dependencies


Move to CDC• Introspection support incompatible

> java.beans.Introspector required by BeanExtender Ruby class

• Solution:> Disable the Ruby beans extension> Serialize Abstract Syntax Tree and redeploy *.ast.ser

files


Evaluating the CDC port• How does downgrading JRuby to 0.8.2 simplify things?

> i.e. Less than 40 locations of java.util.Regex package usage> Less code e.g., 318 source files compared to 574 in 0.9.8

• How does porting to CDC via Java SE simplify things?> Moving closer to CDC gradually> Much fewer new APIs or API differences

– No need for handcrafted porting

• Remember: we’re trying to get to a working subset


Demo on a real device• AWT UI• Can load, modify and launch a script• On device programming


Demo on a real device


Demo on a real device


There's a lot to do from here..


Bringing JRuby to the mobile space• Co-existence of the native and Java options

> Attracts developers from different backgrounds> No reason to limit the hosting platform options

• Anatomy of free open source success> Governance and decision making capability> Tools for collaboration> Strong community values and commitment


Bringing JRuby to the mobile space• JRubME ‘TODO’ list

> Create a mobile spec (desktop too)> Adapt to mobile constraints (ROM, performance, ..)> Rectify the initial porting > Move upwards in the JRuby versions> Migrate to CLDC as well


Bringing JRuby to the mobile space• JRubME ‘Wish-list’

> Scripting languages gain more traction in the mobile space

> CDC (or embedded Java SE flavour) to become the mobile Java de-facto standard

> Dual compilation and JSR-292 (invokedynamic)– Moore’s law will take care of speed

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Thank you

Roy Ben HayunEngineering ServicesCSG

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Date post:	19-Jan-2015
Category:	Technology
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Introduction to JRubMe

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