Os gi introduction made by Ly MInh Phuong-SOC team
Download as PPT, PDF0 likes758 views
OSGi is an architecture that provides a dynamic module system for Java to address issues like JAR dependency management and dynamic loading/unloading of modules. It defines bundles as the basic deployment and versioning unit. Bundles have a lifecycle and can import/export and register/consume services through the OSGi framework and service registry. OSGi aims to provide a dynamic and flexible environment for modular Java applications, especially in embedded, desktop and enterprise domains.
Os gi introduction made by Ly MInh Phuong-SOC team
- 1. OSGi Introduction Ly Minh Phuong – Social Team
- 2. Objective OSGi architecture overview Bundles Services Lifecycle Demo Q&A OSGi framework Motivation
- 3. Why OSGi? Java not support natively dynamic module system.(@2011) JAR dependences management is missing. No way to restrict using class in JAR file.
- 4. Why OSGi? Java not support natively dynamic module system.(@2011)
- 5. Why OSGi? JAR dependences management is missing. What happened when two jar file have duplicate packages and classes ? What happened when your classes only work with a library which version < 2.3.0 ? Can it be prevent in run time ? No way to restrict using class in JAR file. When writing a lib/component can we control what user can import or not ?
- 6. Why OSGi? Resolve in OSGi way.
- 7. What is OSGi OSGi alliance Open Service Gateway initiative Founded 1999 Specification first released in 2000 Newest version of specification is 4.3 (April 2011) Target: embedded, desktop, enterprise application. Widely adopted: Eclipse Equinox, Apache Felix, Glassfish, Knopflerfish, ProSyst, Hitachi SuperJ Engine, …
- 9. Bundle Bundle Basic deployment entity ( app, component, library) Version convention ( major.minor.micro.qualifier ) Specify the dependence, export package, activator Package like JAR file and added the bundle meta info Bundle-ManifestVersion: 2 Bundle-Name: Greeting Client Bundle-SymbolicName: org.foo.hello.client Bundle-Version: 1.2.1.SNAPSHOT
- 10. Bundle Lifecycle
- 11. Bundle dependency resolution The framework prefer already resolved bundle If both are resolved the framework prefer highest matching version. If the version is equal it's prefer the older one.
- 12. Bundle Activator Bundle Activator Define by Bundle-Activator header Handle when bundle start/stop public final class Activator implements BundleActivator{ public void start( BundleContext bc ) throws Exception{ .... } public void stop( BundleContext bc ) throws Exception{ .... } }
- 13. Bundle Mainifest example Bundle-ManifestVersion: 2 Bundle-Name: Greeting Client Bundle-SymbolicName: org.foo.hello.client Bundle-Version: 1.2.1.SNAPSHOT Bundle-Activator : org.foo.hello.client.Activator Import-Package : org.foo.hello;version="[1.0,2.0)" Export-Package : org.org.foo.hello.api;version="1.0" Bundle-ClassPath : .,WEB-INF/classes,WEB-INF/lib/a.jar
- 14. Service Service Bundle can register/unregister service using bundle activator. One service name can have multi provider Service can have properties to describe the service info
- 15. Registering a service Programmatically using Activator Dictionary properties = new Properties(); properties.setProperty("BookStorageType", "MySQL"); bundleContext.registerService(BookStorage.class.getName(), new BookStorageImpl(), properties );
- 16. Consuming a service Programatically using bundleContext.getSerivce() ServiceReference bookStorageRef = bc.getServiceReference(BookStorage.class.getName()); if(bookStorageRef != null){ bookStorage = (BookStorage) bc.getService(bookStorageRef); System.out.println("Got BookStorage Service"); } Use Service Listener Activator.java String filter = "(" + Constants.OBJECTCLASS + "=" + BookStorage.class.getName() + ")"; context.addServiceListener(new BookStorageListener(), filter); BookStorageListener.java class BookStorageListener implements ServiceListener { public void serviceChanged(ServiceEvent event) { .... } }
- 17. Service consuming Use Service Tracker public class XyzServiceTracker extends ServiceTracker { public XyzServiceTracker(BundleContext context) { super(context, ServiceToTrack.class.getName(), null); ... } public Object addingService(ServiceReference reference) { ... } public void removedService(ServiceReference reference, Object service) { context.ungetService(reference); ... } }
- 18. Problems about OSGi OSGi look great but tool and development process not widely public yet. Not every lib is bundle. Version management can be nightmare. Runtime dynamic can result untested situation.
- 19. DEMO
- 20. Q&A