OSGi with the Spring Framework

Baden Basel Bern Brugg Lausanne Zürich Düsseldorf Frankfurt/M. Freiburg i. Br. Hamburg München Stuttgart Wien

Spring DM - OSGi with Spring Framework

Patrick Baumgartner

AD Consultant

[email protected]

Zürich, 10.11.2009

© 2009

Spring Dynamic Modules - OSGi with Spring Framework2

About me

Application Development Consultant

Web development with Spring Framework

OSGi with Spring DM & Spring Framework

Agile Software Development

Certified ScrumMaster

Co-Author of "OSGi in der Praxis“

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Daten sind immer im Spiel.

Agenda

What is OSGi?

The hard-coding Way

Declarative Services

Spring DM

Blueprint Services

Demo

Conclusion

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What is OSGi?

The OSGi framework is a module system for Java that implements a complete and dynamic component model, something that does not exist in standalone Java/VM environments. […] (Source: Wikipedia)

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Bundle Manifest – A special JAR

Image Source: http://www.handycandy.co.uk

http://www.handycandy.co.uk/

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Lifecycle of a Bundle

INSTALL

STARTING

ACTIVE

STOPPING

INSTALLED

RESOLVED

UNINSTALLED

ST

OP

UN

INS

TAL

L UP

DA

TE

R

EF

RE

SH

UN

INS

TAL

L

RE

SO

LVE

START

UPDATE REFRESH

EXCEPTION

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Service Registry

SERVICE REGISTRY

SERVICE CONSUMER

SERVICE PROVIDER

BIND

DISC

OVERR

EGIS

TER

SERVICE DESCRIPTION

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OSGi – A Module System for Java

Clear boundaries

Dependencies

Metadata

Lifecycle

Service Registry

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The hard-coding Way

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The hard-coding Way – Register a Service

Register

ServiceRegistration reg = bundleContext.registerService(ChatterBoxService.class.getName(), twitterChatterbox, properties);

Unregister

reg.unregister();

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The hard-coding Way – Consume a Service

Get Service

ServiceReference ref = bundleContext.getServiceReference(ChatterBoxService.class.getName());

ChatterBoxService chatterbox = (ChatterBoxService)bundleContext.getService(ref);

Unget Service

bundleContext.ungetService(ref);

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The hard-coding Way – Consume a Service

Get Service with ServiceTracker

ServiceTracker tracker = new ServiceTracker(bundleContext, LogService.class.getName(),

serviceTrackerCustomizer);

tracker.open();LogService logService = (LogService) tracker.getService();

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Declarative Services (DS) are part of OSGi R4 Specification – Service Compendium

Declaration of components in XML

OSGI-INF/<component>.xml

Components provides and depend on other Services

Components need a special bundle manifest header

e.g. Service-Component: OSGI-INF/TwitterChatterBox.xml

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<?xml version="1.0" encoding="UTF-8"?><component name="com.trivadis.chatterbox.twitter"> <implementation

class="com.trivadis.chatterbox.twitter.service.internal.TwitterChatterboxServiceImpl"/>

<service> <provide

interface="com.trivadis.chatterbox.service.ChatterBoxService"/> </service><reference name="LOGGER" interface="org.osgi.service.log.LogService" cardinality="0..n" policy="dynamic" bind="addLogService" unbind="removeLogService"/></component>

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Spring Dynamic Modules

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Integration of Springs Dependency Injection and OSGi

Formerly known as Spring OSGi

XML files are located in META-INF/spring

Very similar approach compared to DS

Uses Spring DI for references to other Services and POJOs

(Almost) no dependencies on OSGi APIs

Components need a special bundle manifest headere.g. Spring-Context: META-INF/spring/bundle-context.xml, …

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The Spring DM Idea

APPLICATION CONTEXT

Imported Service

Exported Service

Spring Bean

APPLICATION CONTEXT

APPLICATION CONTEXT

SPRING & SPRING DM

OSGI FRAMEWORK

JVM

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bundle-context.xml

<beans … ><bean id="twitterChatterBox"

class="com.trivadis.chatterbox.twitter.service.internal.TwitterChatterboxServiceImpl"><property name="logService" ref="logServiceOsgi" />

</bean></beans>

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bundle-context-osgi.xml

<beans:beans …>

<service ref="twitterChatterBox" interface="com.trivadis.chatterbox.service.ChatterBoxService"/>

<reference id="logServiceOsgi" interface="org.osgi.service.log.LogService" />

</beans:beans>

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Also supports listeners, filters, and collections

Dynamics are handled by the framework Proxies for service instances and collections Method calls are buffered Configurable timeouts

Annotation-Based Injection with @ServiceReference

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Blueprint Services

Blueprint Services are a Standard since OSGi R 4.2 and based on the Ideas of Spring DM 1.0

Spring DM 2.0 is the Reference Implementation (RI)

Apache Aries Blueprint is an other implementation

Extremely similar to Spring DM but a standard

XML files are located in META-INF/blueprint

Components need a special bundle manifest headere.g. Bundle-Blueprint: OSGI-INF/blueprint/config.xml, …

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Blueprint Services

config.xml

<blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0"> <bean id="twitterChatterBox"

class="com.trivadis.chatterbox.twitter.service.internal.TwitterChatterboxServiceImpl">

<property name="logService" ref="logService" /> </bean>

<service ref="twitterChatterBox" interface="com.trivadis.chatterbox.service.ChatterBoxService" />

<reference id="logService" interface="org.osgi.service.log.LogService" /></blueprint>

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Comparison Spring DM vs. Blueprint Services

Dependency Injection

Constructor Injection

Setter Injection

Field Injection

Method Injection

Arbitrary Method Injection

Autowiring

Spring DM

YES

YES

YES

YES

YES

YES

Blueprint Services

YES

YES

NO

NO

NO

NO

Source: Spring Dynamic Modules Reference Guide 2.0.0.M1

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Comparison Spring DM vs. Blueprint Services

Component Lifecycle

Lazy Initialization

Bean Scopes

Custom Bean Scopes

Built-in Callbacks

Custom Callbacks

Initialization Processing

Spring DM

YES

YES

YES

YES

YES

YES

Blueprint Services

YES

YES

NO

NO

YES

NO

Source: Spring Dynamic Modules Reference Guide 2.0.0.M1

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Demo

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Conclusion

Should I use Declarative Services, Spring DM or Blueprint Services?

DS, DM or Blueprint Services are better than program the life cycles and service infrastructure by hand

If you already use Spring, use Spring DM

If you want to use Standards use DS or Blueprint

To switch from Blueprint Services to Spring DM you need just a few changes in the XML configuration.

?www.trivadis.com

Baden Basel Bern Brugg Lausanne Zürich Düsseldorf Frankfurt/M. Freiburg i. Br. Hamburg München Stuttgart Wien

Thank you!

OSGi with the Spring Framework

Technology

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