Slides of my "OSGi for mere mortals" talk at ApacheCon NA 2011, http://na11.apachecon.com/talks/19416

1. OSGi
for mere mortals
Simple and robus t sof t ware is go o d f or yo ur wor k-life b alance .
Bertrand Delacrétaz
Senior Developer, Adobe Digital Enterprise Systems, www.day.com
Apache So ware Foundation Member and (current) Director
h p://grep.codeconsult.ch - twi er: @bdelacretaz - bdelacretaz@apache.org
ApacheCon North America 2011, Vancouver, November 2011
slides revision: 2011-11-05 (on a plane)
OSGi for 1
Mere Mortals
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2. what?
a simple RESTful server
built from scratch on OSGi
to show that it’s not rocket science,
even starting from scratch...
OSGi for
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3. RESTfulcontent:
POST to store
server?
$ date | curl -T - -X POST -D - http://localhost:8080/store/example
HTTP/1.1 201 Created
Location: /store/example
Content-Type: text/plain; charset=utf-8
Content-Length: 178
Server: Jetty(6.1.x)
Stored at /store/example
StoredBy:ch.x42.osgi.samples.osgi101.app.servlets.StorageServlet
StoredAt:Fri Nov 04 10:41:30 CET 2011
Path:/store/example
Fri Nov 4 10:41:30 CET 2011
OSGi for
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4. RESTful server!
GET to retrieve content:
$ curl http://localhost:8080/store/example
StoredBy:ch.x42.osgi.samples.osgi101.app.servlets.StorageServlet
StoredAt:Fri Nov 04 10:41:30 CET 2011
Path:/store/example
Fri Nov 4 10:41:30 CET 2011
In terms of functionality, that’s it!
OSGi for
Mere Mortals
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5. It’s not big...
107 ./app/pom.xml
35 ./app/.../InMemoryStorage.java
34 ./app/.../PathsStorage.java
147 ./app/.../StorageServlet.java
101 ./core/pom.xml
6 ./core/...CoreConstants.java
32 ./core/...DefaultGetServlet.java
32 ./core/...DefaultPostServlet.java
116 ./core/...DispatcherServlet.java
8 ./core/...Storage.java
208 ./launcher/pom.xml
84 ./launcher/...OsgiBootstrap.java
52 ./pom.xml
962 lines in total, including 468 lines in pom.xml files...
OSGi for
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6. Components
Dynamic Services
Server OSGi framework Application core Application services
Bootstrapping and standard services
HTTP HttpService Dispatcher
InMemoryStorage
Servlet
Services Components
Default POST
Runtime (SCR) StorageServlet
Servlet
Configuration Default GET
PathsStorage
Servlet
Logging
HTTP Felix Web Console
shell Felix Shell
indicates SCR ser vices
also:
maven-bundle plugin
maven-scr-plugin
OSGi for maven-dependency-plugin
Mere Mortals
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7. Bootstrapping
and loading bundles
OSGi for 7
Mere Mortals
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8. Framework start and stop
Called from a plain main() method
OSGi for
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9. Get bundles from Maven repo
Copy to a folder using maven-dependency-plugin in launcher
OSGi for
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10. Install bundles from lesystem
BundleContext.installBundle(URL)
Install all bundles rst, then start all
OSGi for
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11. Live bundles list
From the Felix console at /system/console
We’re good to go!
OSGi for
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12. Our OSGi bundles
HttpService org.apache.felix.h p.je y
Logging org.apache.sling.commons.log
Services Components
Runtime (SCR) org.apache.felix.scr
Configuration
org.apache.felix.metatype
org.apache.felix.con gadmin
Felix Shell
org.apache.felix.shell
org.apache.felix.shell.tui
Felix Web Console org.apache.felix.webconsole
Application Core osgi-for-mere-mortals-core
Application Services osgi-for-mere-mortals-app
OSGi for
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13. Dispatcher
Servlet
OSGi for 13
Mere Mortals
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14. DispatcherServletforComponent
Register with H pService and watch Servlet services
Dispatcher
Servlet
OSGi for
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15. DispatcherServletServlets
Dispatch to OSGi services which are
Dispatcher
Servlet
Default GET
Servlet
OSGi for
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16. Default GET
Servlet
OSGi for 16
Mere Mortals
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17. Default GETSCR annotations
Just a servlet, with some
servlet
Default GET
Servlet
OSGi for
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18. Storage
Services
OSGi for 18
Mere Mortals
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19. Storage service interface
De ned in the core bundle, package is exported
OSGi for
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20. Storage service#1: in memory
Active by default
OSGi for
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21. Storage service#2: can be activated in console
Alternate service, inactive by default,
just paths
OSGi for
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22. Storage
Servlet
OSGi for 22
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23. StorageServlet service
Uses @Reference to get a Storage
Properties used by DispatcherSer vlet
The Component will only start once a Storage service is available
OSGi for
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24. Alternate Storage
demo
OSGi for 24
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25. Replaceone and enabling another ComponentStorage
By disabling
In-memory with paths
1) disable inMemoryStorage -> StorageServlet stops
2) enable PathsStorage -> StorageServlet is back
OSGi for
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26. Con guration
demo
OSGi for 26
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27. Configuring the StorageServlet
Con gurationAdmin service, console and annotations
1) User provides con guration data in web console (or Felix shell, Sling Installer, ...)
Felix Web Console
2) Console (con guration agent) changes values
ConfigurationAdmin StorageServlet
3) Con gurationAdmin deactivates and
reactivates Component with new Con g
0) Component has metatype=true and some
OSGi for non-private @Property annotations
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28. StorageServlet Configuration code
Annotations + read values in activate()
Parameter names + descriptions in metatype.properties
OSGi for
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29. Conclusions
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30. Conclusions
Powerful out of the box
infrastructure, not much
code to write.
Modular component-based
architecture.
Dynamic (re)con guration,
both in terms of components
and parameters.
OSGi materializes the component-based programming
vision in Java, and using it is not rocket science!
Code at github.com/bdelacretaz/OSGi-for-mere-mortals
Your host today: @bdelacretaz, grep.codeconsult.ch
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