jax 09 - osgi service components models

© 2009 Seeberger, Tödter. Released under the Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Germany License. JAX 2009

OSGi ServiceComponent Models

Heiko Seeberger (WeigleWilczek)Kai Tödter (Siemens Corporate Technology)

© 2009 Seeberger, Tödter. Released under the Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Germany License.

OSGi Service Component Models

Agenda

• Why? What?

• OSGi Declarative Services

• Spring Dynamic Modules

• Apache iPOJO

• Guice Peaberry

• Comparison

• Demo

2



Why Components?

3



The OO Dream

4

"Object Oriented technology was going to change the world . . . we would have all these objects in our library and building a new system would be a snap. Just get a few classes,

bunch them together . . . and voila!"Peter Kriens, http://www.aqute.biz/Blog/2006-04-29

http://www.aqute.biz/Blog/2006-04-29

http://www.aqute.biz/Blog/2006-04-29



The OO Reality

5



Coupling!

6

• Classes can almost never be used in isolation

• They depend on other classes

• Those classes depend on other packages, which depend on other JARs . . .



How can Components help?

7



Components ...

8

• are self-contained and declare their dependencies

• declare their interface and hide their internals

• interact with the container and obey to a life cycle



OSGi enables Components

• OSGi Framework is the container

• Managed dependencies

• Life cycle and interactions with the container

• Loose coupling through service model

9



Why Service Component Models?

10



Why not use plain OSGi APIs?

• We want to avoid OSGi glue code

• POJOs enhance testability

• Repetitive glue code reduces productivity

• Service Component Models ease service handling

• OSGi APIs lead to involved code

• SCMs offer advanced features

11



Agenda

• Why? What?



• Apache iPOJO

• Guice Peaberry

• Comparison

• Demo

12



OSGi Framework

Active Bundle

Component

Component Instance

Service

reference

Component Description

Active Bundle

Component

Component Description

Component Instance

provide

OSGi Declarative Services

13



OSGi Framework

DS-powered Bundle

Service ComponentRuntime

createComponent

Service Component Runtime

14



Declaring a Component

15

• Specify component description(s) via Service-Component manifest header

• Specify the implementation class

Service-Component: OSGI-INF/treeView.xml

<component xmlns="http://www.osgi.org/xmlns/scr/v1.1.0"> <implementation class="...TreeView"/></component>



Providing a Service

16

• Specify each service interface

• By default components providing a service are delayed

<service> <provide interface="...IViewContribution"/> <provide interface="...IPersonListener"/></service>



Referencing Services

17

• Specify the service interface

• Specify bind and unbind methods

• Specify the cardinality

<reference interface="...IPersonManager" bind="setPersonManager" unbind="removePersonManager" cardinality="1..1"/>



Concurrency for static and dynamic Policy

18

• No concurrency issues for static policy

• On (un)binding of references the component is deactivated and activated again

• Pay attention to concurrency for dynamic policy

• The component must be thread-safe regarding references

<reference ... policy="dynamic"/>



Agenda

• Why? What?



• Apache iPOJO

• Guice Peaberry

• Comparison

• Demo

19



OSGi Framework

Active Bundle

Application Context

Bean

Service

import

Active Bundle

Application Context

Bean

exportBean

Bean

Bean

Spring Dynamic Modules

20



OSGi Framework

Spring-powered Bundle

Spring DM Extender

createApplication Context

Spring DM Extender

21



Declaring a Bundle Application Context

22

• By default configurations are looked up under META-INF/spring/

• Multiple configurations are merged into a single Application Context



Providing a Service

23

• Specify each service interface or use auto-export

• Beans exported as service cannot be lazy

<osgi:service ref="treeView" auto-export="interfaces" />




24

• A local bean is created with given ID

• Specify the service interface

• Specify the cardinality

<osgi:reference id="personManagerOSGi" interface="...IPersonManager" cardinality="1..1">



Concurrency in Spring DM

• References are only injected once

• Proxies for unary references

• Managed collections for multiple references with “Iterator guarantee”

• Concurrency issue is swapped for uncertainty

• ServiceUnavilableException

25



Agenda

• Why? What?



• Apache iPOJO

• Guice Peaberry

• Comparison

• Demo

26



OSGi Framework

Active Bundle

Component

Component Instance

Service

reference

Component Metadata

Active Bundle

Component

Component Metadata

Component Instance

provide

Apache iPOJO

27



Declaring a Component

28

• Component metadata will be used to instrument the bytecode at build-time

• Specify component and instance

<ipojo> <component classname="...TreeView" /> <instance component="...TreeView" /></ipojo>



Providing a Service

29

• Service interfaces are computed by iPOJO

• iPOJO services are created lazily

<component ...> <provides /></component>




30

• iPOJO offers field and method injection

<requires field="logService" /><requires> <callback type="bind" method="setPersonManager" /> <callback type="unbind" method="removePersonManager" /></requires>



Concurrency in iPOJO

31

• iPOJO manages concurrency for references

• We can write our code without regard for thread-safety

• Bytecode instrumentation weaves in all necessary synchronization



Agenda

• Why? What?



• Apache iPOJO

• Guice Peaberry

• Comparison

• Demo

32



Comparison

33

DS DM iPOJO

POJO-ness + + +

DI power o + o

Ease of programming model o o +

Ease of build + + -

Size and dependencies + - +

Support for laziness + - +



Agenda

• Why? What?



• Apache iPOJO

• Guice Peaberry

• Comparison

• Demo

34



Dynamic Swing OSGi Demo

35



How to get the Demo?

36

• http://max-server.myftp.org/trac/pm

• Wiki with some documentation

• Anonymous Subversion access

• Trac issue tracking

• Licenses

• All PM project sources are licensed under EPL

• Swing Application Framework (JSR 296) implementation is licensed under LGPL

• Swing Worker is licensed under LGPL

• The nice icons from FamFamFam are licensed under the Creative Commons Attribution 2.5 License.

http://max-server.myftp.org/trac/pm


http://www.eclipse.org/legal/epl-v10.html

http://www.eclipse.org/legal/epl-v10.html

https://appframework.dev.java.net/

https://appframework.dev.java.net/

http://www.gnu.org/copyleft/lesser.html


https://swingworker.dev.java.net/

https://swingworker.dev.java.net/



http://www.famfamfam.com/lab/icons/silk/

http://www.famfamfam.com/lab/icons/silk/

http://creativecommons.org/licenses/by/2.5/




© 2009 Seeberger, Tödter. Released under the Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Germany License. JAX 2009

Thank you!Slides at www.slideshare.net/heiko.seeberger/jax-09-osgi-service-components-models

Demo at max-server.myftp.org/trac/pm

http://www.slideshare.net/heiko.seeberger/jax-09-osgi-service-components-models

http://www.slideshare.net/heiko.seeberger/jax-09-osgi-service-components-models



jax 09 - osgi service components models

Technology

derivative works

germany license

service interfacespecify

service model

plain osgi apis

osgi glue code pojos

dynamic policy

static policy