Creating Large Scale Software Platforms with OSGi and an Extension Point Model (EclipseCon)
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OSGi was selected by Nuxeo on the server side 4 years ago in order to create a platform for content management applications that could scale to meet the most challenging digital content use cases. This session will dive into the approach used, how the platform evolved over the past 3 years regarding OSGi, how Nuxeo built the extension system, how to leverage OSGi to create multiple assemblies from the same codebase, discuss how the UI has been modularized, and how the platform can now be deployed on traditional Java server containers and new ones like Eclipse Virgo.
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Creating Large Scale Software Platforms with OSGi and an Extension Point Model (EclipseCon)
- 1. Creating Large-Scale Software Platforms with OSGi and an Extension Point Model Introducing Eclipse Content Repository Bogdan Stefanescu, Lead Architect at Nuxeo 2011-03-23 1
- 2. Nuxeo, Who Are We? ● Vendor of an open source software platform in the feld of Enterprise Content Management ● Love to create great software, fond of modularity, started to use OSGi 4 years ago to create server-side enterprise software ● 10 years old, 500+ customers, 5000+ installations ● Sells support & maintenance subscription and added value software provided as a service ● Dual HQ Paris & Boston, offces in San Francisco ● http://www.nuxeo.com 2
- 3. Nuxeo Enterprise Platform ● The software we develop is an Open Source ECM platform known as Nuxeo Enterprise Platform (EP) ● A platform because you can use Nuxeo EP to develop your own customized ECM application ● We also provide turn-key pre-built applications based on Nuxeo EP already customized for different scopes: – Document Management (DM) – Digital Asset Management (DAM) – Case Management Framework (CMF) – or simply Content Application Platform (CAP) for developers 3
- 4. 4
- 5. Why Are We Here Today? ● To share our experience in building an enterprise application using OSGi and an extension point model ● To discuss and participate into spreading Equinox on the server side as well ● To grab your feedback and ideas! ● And, why not... to do some marketing too ;-) 5
- 6. What Have We Achieved For Now? ● A complex software platform made of ● 186+ bundles, 215+ extension points ● Very fexible thanks to extension points ● Easy to contribute new services ● Easy to customize the default application (including UI and business logic) ● Running virtually everywhere ● JBoss AS - as an EAR application ● Tomcat - as a WAR application ● Equinox - as an OSGi application (and Virgo very soon) 6
- 7. A Bit of History... ● We have been developing this ECM platform for 8 years ● We started in Python ● 5 years ago we switched to Java ● We needed a great model suitable for ● Modularity – split functionality in modules ● Flexibility – be able to easily confgure the application ● Constraints (requested by customers) ● Must deploy as an EAR or WAR application 7
- 8. Choosing the Framework ● What were the choices? ● Java SE – nothing proposed – No bundle life cycle, no modularity, no extension system ● Java EE – not modular at all – All is packaged as one big application (EAR or WAR) – To update or add a feature you need to recompile the entire application ● OSGi – great specifcation – love at frst sight – But not compatible with J2EE – No real OSGi enterprise framework implementations at that moment 8
- 9. Let's Give OSGi a Try... ● OSGi was best suited for our dreams… but... ● How to achieve fexibility? ● Eclipse already had the answer: extension points – Thanks Eclipse! ● How to integrate with J2EE Application Servers? ● J2EE applications are monolithic – there is no notion of modularity inside an application; the application is the unit ● But our application is supposed to be a platform made from tens or hundreds of units! 9
- 10. An Extension Point Model ... ● So Eclipse already provided an extension point model – which is very good but ... ● It is based on EXSD descriptors ● Diffcult to manage EXSD fles outside PDE IDE ● PDE is very related to Eclipse plugin development ● PDE was not friendly with server side development – Remember we are in 2006 ● PDE was not friendly with other build systems – We were using Maven as our build system 10
- 11. Nuxeo Extension Point Model ● So we decided to achieve something similar but in a more fexible way: ● No intermediate object model between services and contributed extensions ● Write your extension class and map it to XML using Java annotations ● Very easy to write for developers ● No specifc IDE needed to code extension points. ● Write a Java class, put the right annotations and the extension XML will be correctly injected into the Java object 11
- 12. Extension Example XML Extension Extension Class 12
- 13. J2EE Integration ● Main problem: different ClassLoader model ● In J2EE an EAR application is the deployment unit and use a fat ClassLoader ● In OSGi an application is made of multiple units (i.e. bundles) each one with its own ClassLoader ● Second problem: static confguration ● In J2EE the application is confgured as a single block using an application.xml and web.xml fle ● In OSGi we can have fragments that can dynamically add confguration 13
- 14. Class Loading Problems ● Running as an EAR application: ● Using a home-made OSGi Adapter to load bundles when the EAR application starts ● Bundles life cycle is preserved ● A fat class loader model is used – All classes are visible to all bundles ● Running as an OSGi application: ● Main problem caused by third party libraries using Class.forName and the Thread Context ClassLoader – Using Eclipse-BuddyPolicy when no other solution is possible 14
- 15. Confguration Fragments – 1 ● On J2EE confguration is monolithic ● To declare servlets you should know in advance what are the servlets provided by different bundles ● Using templates for J2EE confguration fles ● Dynamically generate these fles at application startup from the confguration contributed by bundles ● Able to package EAR applications that can adapt themselves to the confguration provided by application bundles ● No need of having different product packagings for different confgurations 15
- 16. Confguration Fragments – 2 conf guration fragment i web.xml template. ID: web 16
- 17. J2EE Features Added to OSGi ● Full OSGi integration of JAAS – for the authentication system ● Full JTA (transactions) support through Apache Geronimo ● Full JCA (resource adapters and pooling) support through Apache Geronimo ● In-memory JNDI server ● Future plans to integrate the work done in the Gemini project (and also support Virgo) 17
- 18. Where Are We Going? ● Contribute the core of Nuxeo EP to Eclipse ● ECR (Enterprise Content Repository) project is in the proposal phase ● https://github.com/nuxeo/org.eclipse.ecr ● Port all major Nuxeo EP services as ECR plugins ● For now only the core functionality is included in ECR ● Help us provide the frst OSGi-based ECM platform based on the ECR project! 18
- 19. Questions? Start Hacking ECR: https://github.com/nuxeo/org.eclipse.ecr Get Involved: ECR Proposal Forum Read more: Eclipse ECR Proposal Nuxeo EP Reference Documentation Contact me/us: Bogdan Stefanescu - [email protected] http://www.nuxeo.com 19