appengine ja-night-10

Mirah & DubiousMirah & Dubious

Tuesday, August 31, 2010

Mirah & DubiousA bold and beautiful way to write Java, plus a new framework for App Engine

Charles NutterJohn WoodellAug 30, 2010

2


MirahA pragmatic blend of Ruby and Java


Me

• Charles Oliver Nutter

• Engine Yard, Inc

• [email protected]

• @headius

• JRuby core developer

• Mirah creator


mailto:[email protected]

mailto:[email protected]

Ruby

• Beautiful language

• Clean syntax

• Easy-to-use closures

• Nice core libraries

• “Slow” language

• Very dynamic == hard to optimize


Java

• High-performance language

• Mostly static typing

• Full system optimizations

• Primitive math operations

• Ugly language

• (C++)-- of 1995


Mirah

• “Apparent features” of Ruby

• Syntax

• Closures and iterators

• Dynamic-feeling behaviors

• Performance, typing like Java

• As fast as Java for almost everything


What If This...public class Foo { private int a;

public Foo(int a) { this.a = a; }

public void show() { System.out.println(a); }}


...Could Be Thisclass Foo def initialize(a) @a = a end

def show puts @a endend


Mirahclass Foo def initialize(a:int) @a = a end

def show puts @a endend


“Java’s Ruby”

• A nicer way to write Java

• Ruby syntax with modifications

• Feels like Ruby

• Compiles to Java/JVM

• No runtime library


Features From Ruby

• Optional arguments ✓

• Internal iteration ✓

• Closures ✓

• Literals ✓

• String interpolation ✓

• Mixins, “open” classes (soon)


Features From X

• (Coming Soon)

• Extension methods (C#ish, but nicer)

• Implicit type conversions (Scala)

• Pattern matching?

• Case classes?


Ruby

puts “Hello, world!”


Mirah

puts “Hello, world!”


Mirah

// Generated from DashEpublic class DashE extends java.lang.Object { public static void main(java.lang.String[] argv) { java.io.PrintStream temp$1 = java.lang.System.out; temp$1.println("Hello, world!"); }}


Ruby

def fib(a) if a < 2 a else fib(a - 1) + fib(a - 2) endend


Mirah

def fib(a:int) if a < 2 a else fib(a - 1) + fib(a - 2) endend


Mirah

// Generated from DashEpublic class DashE extends java.lang.Object { public static void main(java.lang.String[] argv) { } public static int fib(int a) { return (a < 2) ? (a) : ((DashE.fib((a - 1)) + DashE.fib((a - 2)))); }}


Ruby

def foo(a = 1, b = 2) puts a + bend


Mirah

def foo(a:int = 1, b:int = 2) puts a + bend


Mirah public static java.io.PrintStream foo(int a, int b) { java.io.PrintStream temp$1 = java.lang.System.out; temp$1.println((a + b)); return temp$1; } public static java.io.PrintStream foo() { return foo(1); } public static java.io.PrintStream foo(int a) { return foo(a, 2); }


Ruby

a = [5,4,3,2,1]a.each do |x| puts xend


Mirah

a = [5,4,3,2,1]a.each do |x| puts xend


Mirah// Generated from DashEpublic class DashE extends java.lang.Object { public static void main(java.lang.String[] argv) { java.util.List a = java.util.Collections.unmodifiableList( java.util.Arrays.asList(1, 2, 3, 4, 5)); java.util.Iterator __xform_tmp_1 = a.iterator(); label1: while (__xform_tmp_1.hasNext()) { java.lang.Object x = __xform_tmp_1.next(); label2: { java.io.PrintStream temp$3 = java.lang.System.out; temp$3.println(x); } } }}


Ruby

t = Thread.new do puts “in thread”end


Mirah

t = Thread.new do puts “in thread”end


Mirah// Generated from DashEpublic class DashE extends java.lang.Object { public static void main(java.lang.String[] argv) { DashE.__xform_tmp_1 $binding = new DashE.__xform_tmp_1(); $binding.x = "in thread"; java.lang.Thread t = new java.lang.Thread(new DashE.__xform_tmp_2($binding)); } public static class __xform_tmp_1 extends java.lang.Object { java.lang.String x; } public static class __xform_tmp_2 extends java.lang.Object implements java.lang.Runnable { private DashE.__xform_tmp_1 binding; public __xform_tmp_2(DashE.__xform_tmp_1 binding) { this.binding = binding; } public void run() { DashE.__xform_tmp_1 $binding = this.binding; java.io.PrintStream temp$1 = java.lang.System.out; temp$1.println($binding.x); } }}


Open Class (proposal)interface StringFunc def apply(str:String)end

extend class String # java.lang.String def each(func:StringFunc) # String#split call from Java lines = split

# like “for (String str: strArray)” lines.each do |str| func.apply(str) end endend


Open Class (Java side)

public interface StringFunc { public void apply(String str);}

public class StringExtension { public void each(String str, StringFunc func) { for (String s: str.split()) { func.apply(str); } }}


Open Class (usage)

str = “hello\ngoodbye\nworld”

str.each {|s| ... }


Open Class (Java usage)

String str = “hello\ngoodbye\nworld”;

StringExtension.each(str, new StringFunc() { public void apply(String s) { ... }});


Open Class (Java usage)

String str = “hello\ngoodbye\nworld”;

StringExtension.each(str, new StringFunc() { public void apply(String s) { ... }}); YUCK!


Type Conversion


# no “map” method on String...str.map {|s| # ERROR


Type Conversion(by hand)


# without type conversionArrays.asList(str.split).map { ...


Type Conversion (proposal)

conversion(String => List) do |str| Arrays.asList(str.split)end

conversion(List => String) do |list| list.join(‘\n’)end


Type Conversion (usage)


# with type conversion!str.map { ... # OK!!


It’s Not Ruby

• Using Java’s libraries and type system

• No “eval”

• No runtime-mutable classes

• Ruby libraries will not work


But It Feels Like Ruby!

• Clean, lightweight syntax

• Iteration, closures

• Far less “ceremony” than Java

• Performance equivalent to Java


mirah.org


DubiousDubiousはMirahのWebフレームワーク


Me

• John Woodell

• Web developer at Google

• Dubious creator

• App Engine JRuby maintainer

• @JohnWoodell


47

Thank you for using"AppEngine/Java”

いつも"AppEngine/Java"をご利用頂きありがとうございます


48

Spin-up time can make scaling “painful”• The most critical issue to be resolved is spin-up time,

App Engine scales by adding new application instances.• Even if initialization could happen without affecting users

some apps will need to scale instantly.


49

Spin-up?Yes, this is a problem...

そうですね。使い物にならないですよね


50

...but now you can useMirah and Dubious

ならば "Mirah/Dubious" だ


51

Dubious is Web framework for Mirah

DubiousはMirahのWebフレームワーク

*du・bi・ous[ djbis | dj- ] [形]

[1] ((叙述))〈人が〉（…に）半信半疑の；怪しいと思う，疑う((of, about, as to ...)).

[2] 〈人・性質・行為が〉いかがわしい，怪しい；（真実性などが）疑問である，不審な；

〈称>号・栄誉などが〉ありがたくない


52

Write Rails-style code,

it runs on Google App Engine

ターゲットはGoogleAppEngine

Railsっぽく書けます


53

Benefits of Mirah on App Engine• Ruby syntax & apparent features + Java type system• Use Java or Ruby when Mirah lacks features you require• The generated Java source can be inspected at any time• Macros and plugins can be written in Ruby or Mirah• New instances always spin-up in about a second


54

Working with Dubious• Dubious framework uses familiar Rails conventions• Generate JSONs or work with ERb templates• MirahModel syntax is similar to DataMapper• Developers can create apps entirely in Rails,

then refactor URLs that need to scale quickly• Some important features are currently missing,

but “you” could have fun contributing them


55

Here’s code from Dubious(this is not Rails)

これらはRailsではなくDubiousのコードです


Dubious controllers will be familiar


Mirah can use ERb templates


The generated Java source can be inspected


The ERb is transformed into method calls


Your model definition is very concise


Code generation based on defined properties


All the basic methods you need are generated


63

It really works,

and spins-up in ~1sec

ちゃんとうごきます。しかも、爆速Spinup.


64

It isn’t "Dubious"あやしくないよ。

http://dubious-demo.appspot.com




The Framework(coding in Mirah)


Method signatures enforce types


Return type can be enforced also


Code is very concise


Thank YouThank You


appengine ja-night-10

Technology

dashe public class dashe

new java

public static class

private dashe

java ruby syntax

threadnew dashe

public static void mainjava

dashemirahpublic class