osgi in action bluedavy 1.1 2007-10-20

OSGi in action

BlueDavyhttp://www.osgi.org.cnhttp://blog.bluedavy.cn

1.12007-10-20

23/4/2023/4/20 22 OSGi China User Group: http://www.osgi.org.cn 致力于致力于 OSGiOSGi 的推广和发的推广和发展展

Agenda Use OSGi with popular framework Deploy exist system to OSGi The feature of OSGi application OSGi application design best practices OSGi application develop best practices Resources


Use OSGi with popular framework Use with Hibernate Use with Spring Use with Webwork Intergration key factors


Use with HibernateDownload Hibernate-OSGi

http://www.osgi.org.cn/Hibernate-OSGi; install cn.org.osgi.hibernate bundle or import Hibernat

e-OSGi source project to eclipse.

Write demo bundle with Hibernate-OSGi to use Hibernate


Use with HibernateChange the connection info in hibernate.cfg.xml

of cn.org.osgi.hibernate bundle;New Plug-in project,and write persistent class as

you always do,then generate persistent class hbm file;

Implemention DAO class with cn.org.osgi.hibernate.service.CommonDaoService or other common Hibernate DAO API;


Use with HibernateRegister Persistent class as extension point;

create plugin.xml,then input following content into the file,just like this:

– <extension point=“cn.org.osgi.hibernate.PoExtension">– <po class="cn.org.osgi.bulletin.po.Bulletin"/>– </extension>

Start the application,then finish the demo that use OSGi with Hibernate


Use with Hibernate Summary

the difference between use with hibernate and use with OSGi & hibernate only two sides:

– don’t add resource mapping element to hibernate.cfg.xml any more;

– Use extension point to register po.


Use with Hibernate The implemention method of Hibernate-OSGi

Refactor AbstractClassGenerator.getClassLoader() method to sure use the AbstractClassGenerator class’s classloader to load the associate class

– Why do this?– Just because AbstractClassGenerator use po class’s classload

er to load cglib associate class,but now the bundle including po class don’t need import cglib jar.

Based on extension point to register/unregister po– Why do this?

– Just because module seperation rule.– Use extension point so we can register po outside of Hibernate

Module.

– The session service use Configuration.addClass to register po from other bundle.


Use with HibernateThe weakpoint of Hibernate-OSGi

Not support many hibernate po advanced configuration just like po class cache etc. currently;

Not support multi sessionfactory currently; Need support register connection info from other bund

les; When new pos added or exist pos removed,SessionF

actory need be restarted;

Let’s improve Hibernate-OSGi together If u want to join this group,pls visit this webpage:

– http://www.osgi.org.cn/Hibernate-OSGi/join.html


Use with SpringDownload Spring-OSGi;

http://www.springframework.org/osgi

Create the build and run environmentPublish Spring bean as OSGi serviceInject OSGi service to Spring beanBest practicesThe weakpoint of Spring-OSGi


Use with Spring Create the build and run environment

install these bundles to eclipse or equinox– aopalliance

– aspectjrt

– backport-util-concurrent

– spring-aop

– spring-aspects

– spring-beans

– spring-context

– spring-core

– spring-dao

– spring-osgi-core

– spring-osgi-extender

– spring-osgi-io


Publish Spring bean as OSGi serviceIt’s very simple to do this

just write this element– <osgi:service id=“serviceID” ref=“spring bean name” interfac

e=“OSGi service interface”/>– You can add osgi:service-properties to realize the properties

configuration in OSGi component’s xml


Inject OSGi service to Spring bean It’s also very simple to do this, just write this element

<osgi:reference id=“Just like Spring bean name” interface=“OSGi service ” cardinality=“[0..n]|[0..1]|[1..n]” filter=“” timeout=“” depends-on=“” context-classloader=“”/>

We can use two method to inject this OSGi service to spring bean

– <bean name=“bean name” class=“bean class”><property name=“OSGi service” ref=“OSGi reference id”/> </bean>

– add osgi:listener to osgi:reference– <osgi:listener ref=“the spring bean name need inject this OSGi service”

bind-method=“inject OSGi service’s method name” unbind-method=“when OSGi service unavaible,then call this method”/>

– The bind-method need change to this kind signature public void some-method-name(service interface,Dictionary)

The difference between these two methods– The first method cann’t get the OSGi service’s dynamic changinatio

n,but the second method can do this.


Best practicesOnly publish those pojo needed export as OSGi

service;Use osgi:listener method to inject OSGi service t

o spring bean;Handle the OSGi service dynamic change;If can publish the pojo in DS style,then use DS st

yle;


The weakpoint of Spring-OSGiCann’t dynamic load spring bean bundle;Spring-OSGi bundle must start before other bun

dles;Spring-OSGi depends excessive bundles.


Use with WebworkDownload Webwork-OSGi

http://www.osgi.org.cn/Webwork-OSGi Install cn.org.osgi.webwork bundle or Import Webwor

k-OSGi project to eclipse The bundle did realize webwork intergration with Spri

ng-OSGi

Write demo bundle with Webwork-OSGi to use webwork with OSGi


Use with Webwork New Plug-in project,write action class and action xml as always you

do; <action name="list" class="LIST"> Class property upside map to its OSGi service’s property

– <property name="command" value="ADMINLOGIN"/>

Publish action class as OSGi service in ds style or spring-OSGi style;

Export the package where your action classes and action resource files in;

Register action xml file to extension point; <extension point=“cn.org.osgi.webwork.actionextension"> <action configFile="cn/org/osgi/bulletin/list/action/xwork.xml"/> </extension>

Start the application,then u can visit the action


Use with WebworkSummary

the difference between use with webwork and use with webwork-OSGi

– the action class property is not the action class true name,but is the osgi service command property the action class published;

– the action xml file is not write to a singlepoint xwork.xml,but register to webwork-OSGi based on extension point;


Use with WebworkThe implemention of Webwork-OSGi

Write own action xml file configuration provider class– so webwork-OSGi can dynamic load and unload action xml fil

e outside webwork-OSGi bundle;

Write own ObjectFactory to load action and other class

– so webwork-OSGi can load action class instance from OSGi service registration and then realize intergration with spring-OSGi;

– Other class loading as webwork always do

Change webwork action xml file configuration provider and ObjectFactory


Use with WebworkThe weakpoint of Webwork-OSGi

Maybe we need write a webwork-OSGi bundle so when webwork update,we can update quickly;

Not support servlet filter configuration,but this is httpservice problem


Intergration key factorsClassloader factor

Can use OSGi Dynamic-ImportPackage and Export-Package to solve this factor.

Resource loader factor Can use extension point to realize load resource dyna

mically and so resource can be placed in module style.

The most important factor:”modularity” & “Plug and Play”


Deploy exist system to OSGiUse bnd tool to do this

http://www.aqute.biz/Code/Bnd http://www.aqute.biz/Code/BndCn

Step Separate project packages in module style logically; Define module need import package and export pack

age; Write bnd file for per module; Run bnd tool then get the module jar file; Deploy the module jar file to OSGi framework


The feature of OSGi applicationStrict and clear modularity

Quickly know the module dependency; Quickly know the module exported function; Quickly know how the module can be extensioned;

Reusable Build company bundle respository

Dynamic “Plug and Play”

Extensionable


OSGi app design best practicesClear and strict define module;

Module’s Export Function; Module’s Dependency; Module’s Extension Point;

Interface-oriented and SOCM; Bundles compose of components,components comm

unicate each other with OSGi service; All service publish in interface type;

Split Interface & Implemention into separate bundles;


OSGi app develop best practicesKeep the dynamic feature

Don’t suppose the dependence service usable; Handle the dynamic change such as extension added

/event published/service unavaible;

If the service is used only inside bundle,then don’t publish it as OSGi service;

Don’t make static dependency to other bundles;


ResourcesOSGi R4 Specifications 《 OSGi 实战》 Opendoc 《 OSGi 进阶》 Opendoc http://www.osgi.org http://www.osgi.org.cn http://www.aqute.biz http://blog.bluedavy.cn

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OSGi China User Group http://www.osgi.org.cn

osgi in action bluedavy 1.1 2007-10-20

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