OSGi with the Spring Framework

Spring DM - OSGi with Spring Framework
Patrick Baumgartner
AD Consultant
patrick.baumgartner@trivadis.com
Zürich, 10.11.2009

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“
Spring Dynamic Modules - OSGi with Spring Framework
2

Agenda
What is OSGi?
The hard-coding Way
Declarative Services
Spring DM
Blueprint Services
Demo
Conclusion
3

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)
4

Bundle Manifest – A special JAR
5
Image Source: http://www.handycandy.co.uk

Lifecycle of a Bundle
6
UPDATE REFRESH
INSTALL
STARTING
INSTALLED
START
UPDATE REFRESH
RESOLVE
EXCEPTION
ACTIVE
RESOLVED
UNINSTALL
UNINSTALL
STOP
STOPPING
UNINSTALLED

Service Registry
7
SERVICE REGISTRY
REGISTER
DISCOVER
SERVICE DESCRIPTION
BIND
SERVICE CONSUMER
SERVICE PROVIDER

OSGi – A Module System for Java
Clear boundaries
Dependencies
Metadata
Lifecycle
Service Registry
8

The hard-coding Way
9

The hard-coding Way – Register a Service
Register
ServiceRegistration reg = bundleContext.registerService( ChatterBoxService.class.getName(), twitterChatterbox, properties);
Unregister
reg.unregister();
10

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);
11

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();
12

13

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 headere.g. Service-Component: OSGI-INF/TwitterChatterBox.xml
14

<?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>
15

Spring Dynamic Modules
16

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, …
17

The Spring DM Idea
18
APPLICATION CONTEXT
APPLICATION CONTEXT
APPLICATION CONTEXT
Imported Service
Exported Service
Spring Bean
SPRING & SPRING DM
OSGI FRAMEWORK
JVM

bundle-context.xml
<beans … >
<bean id="twitterChatterBox"class="com.trivadis.chatterbox.twitter.service.internal.TwitterChatterboxServiceImpl">
<property name="logService" ref="logServiceOsgi" />
</bean>
</beans>
19

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
21

Blueprint Services
22

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, …
23

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
25
Spring DM
Blueprint Services
Constructor Injection
Setter Injection
Field Injection
Method Injection
Arbitrary Method Injection
Autowiring
YES
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
Source: Spring Dynamic Modules Reference Guide 2.0.0.M1

Comparison Spring DM vs. Blueprint Services
Component Lifecycle
26
Spring DM
Blueprint Services
Lazy Initialization
Bean Scopes
Custom Bean Scopes
Built-in Callbacks
Custom Callbacks
Initialization Processing
YES
YES
YES
YES
YES
YES
YES
YES
NO
NO
YES
NO
Source: Spring Dynamic Modules Reference Guide 2.0.0.M1

Demo
27

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.
28

Thank you!

OSGi with the Spring Framework

by Patrick Baumgartner on Nov 11, 2009

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OSGi with the Spring Framework — Presentation Transcript