OSGi for mere mortals
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The document presents a straightforward approach to building a RESTful server using OSGi, emphasizing its accessibility and efficiency. It details the server's functionalities, including content storage and retrieval, as well as the minimal code required to implement it. The presentation also highlights the importance of OSGi's modular architecture and dynamic configuration capabilities.
OSGi for mere mortals
- 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 1
- 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 Mere Mortals 2
- 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 Mere Mortals 3
- 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 4
- 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 Mere Mortals 5
- 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 6
- 7. Bootstrapping and loading bundles OSGi for 7 Mere Mortals 7
- 8. Framework start and stop Called from a plain main() method OSGi for Mere Mortals 8
- 9. Get bundles from Maven repo Copy to a folder using maven-dependency-plugin in launcher OSGi for Mere Mortals 9
- 10. Install bundles from lesystem BundleContext.installBundle(URL) Install all bundles rst, then start all OSGi for Mere Mortals 10
- 11. Live bundles list From the Felix console at /system/console We’re good to go! OSGi for Mere Mortals 11
- 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 Mere Mortals 12
- 13. Dispatcher Servlet OSGi for 13 Mere Mortals 13
- 14. DispatcherServletforComponent Register with H pService and watch Servlet services Dispatcher Servlet OSGi for Mere Mortals 14
- 15. DispatcherServletServlets Dispatch to OSGi services which are Dispatcher Servlet Default GET Servlet OSGi for Mere Mortals 15
- 16. Default GET Servlet OSGi for 16 Mere Mortals 16
- 17. Default GETSCR annotations Just a servlet, with some servlet Default GET Servlet OSGi for Mere Mortals 17
- 18. Storage Services OSGi for 18 Mere Mortals 18
- 19. Storage service interface De ned in the core bundle, package is exported OSGi for Mere Mortals 19
- 20. Storage service#1: in memory Active by default OSGi for Mere Mortals 20
- 21. Storage service#2: can be activated in console Alternate service, inactive by default, just paths OSGi for Mere Mortals 21
- 22. Storage Servlet OSGi for 22 Mere Mortals 22
- 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 Mere Mortals 23
- 24. Alternate Storage demo OSGi for 24 Mere Mortals 24
- 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 Mere Mortals 25
- 26. Con guration demo OSGi for 26 Mere Mortals 26
- 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 Mere Mortals 27
- 28. StorageServlet Configuration code Annotations + read values in activate() Parameter names + descriptions in metatype.properties OSGi for Mere Mortals 28
- 29. Conclusions 29
- 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 OSGi for Mere Mortals 30