PojoSR or OSGi (µ)Services For the Rest of Us

PojoSRor(OSGi)µServicesfortherestofus

KarlPauls

!"#$%&'&()"*Dienstag, 25. Oktober 2011

Karl

• MemberApacheSo?wareFoundaDon

• PMC:Felix,Sling,Incubator

• PPMC:Ace,Clerezza,Celix

• FellowatLuminis

• ProjectOwnerPojoSR

• Co‐Authorof„OSGiinAcDon“

• [email protected]

([email protected])

Hallet al.

OSGiIN ACTION

M A N N I N G

Richard S. HallKarl Pauls

Stuart McCullochDavid Savage

FOREWORD BY PETER KRIENS

Creating Modular Applications in Java

Dienstag, 25. Oktober 2011

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mailto:[email protected]?subject=

mailto:[email protected]

mailto:[email protected]

ServiceOrientaDon


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µServices


µServices

• Interface‐basedprogramming,butmore

• ServiceRegistry

• Centrallyaccessible

• Browsable

• NoDficaDons

• ServiceRegistryBenefits

• ConsumingcodeisincontrolofproviderselecDon

• ButnotproviderinstanDaDonandconfiguraDon

• Providercodeisincontrolofwhentoprovide

• Promotesveryloosecouplingandlatebinding


OSGi(µ)Services


OSGiservices

• OSGiframeworkprovidestheconceptsweneed

• Centralizedserviceregistry

• ConsumerhascontroloverselecDon

• Providerhascontroloverwhentoprovide

• Plusfull‐blowndeploymentandpackagingmodularitywithrun‐Dmedynamism


OSGi


OSGi

• ThedownsidetoOSGiisthatitrequiresaboSom‐upcommitment

• Youneedtoconvertallofyourcodeintopropermodulestotakeadvantageofservices

• Atop‐downapproachofadopDngservicescanhelpeasemigraDontomoremodularcode


OSGiframework


PojoSR


WhatisPojoSR?

• ItlargelyremovesthemodularitylayerfromtheOSGiframework

• Provides

• AcentralizedserviceregistrybasedonOSGiAPI

• LifecyclehooksforJARfiles

• A“light”OSGiframeworkfortheclasspath


Whythisapproach?

• OSGiAPIisastandardwithyearsofexperiencebehindit

• Canre‐useOSGimodules(a.k.a.bundles)and/ortechnology

• Canleverageserviceswithouthavingtocompletelymodularizefirst(i.e.,top‐down)

• Providesapathtofull‐blownmodularity


UseCases


MigraDon


MigraDon

• WithoutPojoSR

• TurnapplicaDonintoonebigbundle(jar)

• Splitintoseveralbundles

• Fixproblems

• Splitintoevenmorebundles(etc.)

• Eventually,startusingservices

• Allowsyoutoremoveuglyhacksneededtofixproblems

• WithPojoSR

• Startusingservices

• SplitintobundlesDienstag, 25. Oktober 2011

UseOSGiwhereyoucan‘t

• OSGi(lite)onGoogleAppEngineusingPojoSR


UseOSGiwhereyoucan‘t

• hSp://vimeo.com/22571224


http://vimeo.com/22571224

http://vimeo.com/22571224

Android


Commondiscovery(SPI)


ServicesanddependencyinjecDon

• AdvantageswhencombinedwithserviceorientaDon

• DependencyinjecDonnolongerneedsglobalview

• InformaDonlocalizedtojusttheprovider/consumer

• NolongerrestrictedtoasingleDIframework

• DifferentDIframeworkscanplaytogetherviatheserviceregistry


Usage


AsaServiceRegistry


AsanOSGi„light“framework


Standalone


Demo


ClosingRemarks


BenefitsandDrawbacks

• PojoSRprovidespartofthepowerofOSGi

• inanon‐intrusiveway.

• allowstoincreasemodularityanduseµServices

• withoutfirstriddinganexisDngcodebaseofclassloaderhacks

• CanrunOSGibundleswhereyoucan‘t

• Thedrawbacksare

• doesnotenforcesmoduleboundaries

• doesnotallowmulDpleversionsofthesamepackage;doesnotsupporttheBundle‐ClassPath.

• ButyoucanusetheµServicemodeltogetridoftheclassloadinghacksoverDme,a?erwhichitwillbeeasiertomovetoOSGiandgetsidebysideversioningandrealmoduleboundaries.


QuesDons?

http://pojosr.googlecode.com




PojoSR or OSGi (µ)Services For the Rest of Us

Technology

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