OUGF - OSGi / Flex
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This document discusses building modular rich internet applications (RIAs) using Flex and OSGi. It provides an overview of Flex, OSGi, and how they can interact. Key points covered include communicating between Flex and OSGi services via RemoteObjects and Producer/Consumer, defining strongly typed objects, and building modular applications by creating Flex modules that package UI and logic into individual OSGi bundles. The document demonstrates how this approach allows splitting applications into independently deployable pieces to improve modularity.
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OUGF - OSGi / Flex
- 1. Building complex and modular RIAs with OSGi and Flex francois.fornaciari@zenika.com www.zenika.com
- 2. Agenda • Introduction • Flex and OSGi interactions • Application modularization • Demo • Conclusion www.zenika.com
- 3. What is Flex (1/2) • Framework for building RIA • Flash technology • Free Software Development Kit (SDK) • Flash Player (VM) • Strong integration with Java • Tooling • Flash Builder : IDE based on Eclipse • IntelliJ IDEA www.zenika.com
- 4. What is Flex (2/2) • MXML: XML-based language • ActionScript: ECMAScript-compliant scripting • Library of pre-built components • Compiler: create SWFs from MXML/ActionScript www.zenika.com
- 5. MXML • XML-based language • Declarative way to build applications <s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark" xmlns:mx="library://ns.adobe.com/flex/mx"> <s:Panel> <s:Label text="Label" /> <s:Button label="Button" /> </s:Panel> </s:Application> www.zenika.com
- 6. ActionScript • Core of the Flex Framework • ECMAScript-compliant scripting • Familiar syntax package com.zenika.flex { public class MyClass interface MyInterface { public function MyClass() { } public function doSomething():String { } } } www.zenika.com
- 7. What is OSGi (1/3) • A module system and service platform for the Java programming language • OSGi framework specifications • Core Specification • Compendium Specification • Enterprise Specification www.zenika.com
- 8. What is OSGi (2/3) • Service Oriented Architecture Service broker Lookup Register Specification Binding Consumer Provider www.zenika.com
- 9. What is OSGi (3/3) • Bundle • Deployment unit: JAR + MANIFEST • Functional unit (provides services) • Application • Set of bundles • Dynamically deployed • Potentially shared between applications www.zenika.com
- 10. Purpose • Presentation of the main design patterns for building complex and modular applications with Flex and OSGi • Two axes • Communication between Flex and OSGi • Application modularization www.zenika.com
- 11. General architecture Client (browser) Server (Java) Flex HTTPService OSGi Framework WebService RemoteObject Producer SWF Application SWF Module SWF Module Consumer Bundle Bundle Bundle www.zenika.com
- 12. Handling remote calls • HTTPService, WebService, Remote Objects, Consumer/Producer • Asynchronous calls • Result, Fault or Message handlers • Arguments and result types • Strongly typed or generic objects • XML format • Properties • URL, destination, endpoint, id, … www.zenika.com
- 13. Service call example private function callService():void { var service:MyService = new MyService(destination); service.addEventListener(ResultEvent.RESULT, onResult); service.addEventListener(FaultEvent.FAULT, onFault); service.send(); } private function onResult(event:ResultEvent):void { var result:MyObject = event.result as MyObject; ... } private function onFault(event:FaultEvent):void {...} www.zenika.com
- 14. Communications (1/2) • Accessing “non-OSGi services” • HTTPService • Supported methods: GET | POST • HEAD | OPTIONS | PUT | TRACE | DELETE only through the server-based proxy service • WebService • Provides access to SOAP-based web services on remote servers • ex: exposed through D-OSGi www.zenika.com
- 15. Communications (2/2) • Accessing “OSGi services” • In a transparent way • Two communication types • RemoteObject • Simple call to an existing OSGi service • Strongly-typed arguments and result or … • … generic objects • Unsafe access to properties and methods • Introspection API • Producer/Consumer • Topic subscription www.zenika.com
- 16. AMF Protocol (1/2) • Action Message Format (v3) • Binary format used to serialize ActionScript objects • Optimized transferred data amount • Primarily used to exchange data between Adobe Flash applications and remote services • Specification since 2007 • Supported by many server-side languages and technologies: Java, .NET, PHP, … www.zenika.com
- 17. Integration frameworks • Existing open source frameworks Name OSGi support RemoteObject Producer / Consumer AMF3 for OSGi (LGPL) yes yes yes GraniteDS (LGPL) yes (prototype) yes (unstable) no Spring Flex (ASL) yes (Virgo) yes yes • AMF3 for OSGi (Christopher Brind) • Easy to use • Only 3 bundles to deploy • Robust www.zenika.com
- 18. AMF3 for OSGi • OSGi bundles description • uk.co.arum.osgi.amf3 • Serialization-deserialization of AMF3 objects • uk.co.arum.osgi.amf3.http • Registers an HTTP servlet that is capable of reading and writing AMF3 objects • uk.co.arum.osgi.amf3.flex.remoting • Implements FlexRemoting over HTTP • Provides support for channel based messaging www.zenika.com
- 19. Apache Felix projects (1/2) • Core of the server-side application • Framework • File Install • Directory based OSGi management agent • Used internally by AMF3 for OSGi • Declarative Service (SCR) • Event Admin Service • Log Service • HTTP Service (Jetty) www.zenika.com
- 20. Apache Felix projects (2/2) • Application-specific projects • Event Admin Service • OSGi EventHandler receives messages from Flex Producers • Messages posted by the OSGi EventAdmin service are received by Flex Consumers • iPOJO • Used to declare OSGi components • Support of annotations • Extensible handlers www.zenika.com
- 21. Publishing OSGi services • Additional service property • AMF_SERVICE_NAME • Instantiated with the service class name @Component(name="MyService") @Provides public class MyServiceImpl implements MyService { @ServiceProperty(name="AMF_SERVICE_NAME") private String serviceName = MyService.class.getName(); ... } www.zenika.com
- 22. Consuming OSGi services • Flex RemoteObject • Endpoint: AMF3 servlet path ex: http://localhost:8080/amf3osgi • Destination: OSGi service class name <s:RemoteObject id="myService" endpoint="/amf3osgi" destination="com.zenika.service.MyService"> <mx:method name="doSometing" result="onResult(event)" fault="onFault(event)" /> </s:RemoteObject> www.zenika.com
- 23. Type-safe objects • Method arguments and result [RemoteClass(alias="com.zenika.systemmanager...SWFModule")] [Bindable] public class SWFModule www.zenika.com
- 24. Producer / Consumer (1/2) • Bridge between Flex events and EventAdmin service • Elements attributes • Consumer: callback when a message is received • Consumer and producer: destination <mx:Consumer message="onMessage(event)" destination="events" fault="onFault(event)" /> <mx:Producer destination="events" fault="onFault(event)" /> www.zenika.com
- 25. Producer / Consumer (2/2) • Destination configuration • Set of channels used to send messages to a target destination • QoS: many channels for network failure tolerance var channelSet:ChannelSet = new ChannelSet(); var channel:AMFChannel = new AMFChannel("events","/amf3osgi"); channel.pollingInterval = 5000; channelSet.addChannel(channel); consumer.channelSet = channelSet; www.zenika.com
- 26. Sending messages (1/2) • From OSGi • PublishedObjectEvent (channelID, object) • Extends org.osgi.service.event.Event @Bind public void bindEventAdmin(EventAdmin eventAdmin) { this.eventAdmin = eventAdmin; } private void sendMessage() { eventAdmin.postEvent( new PublishedObjectEvent("events", object)); } www.zenika.com
- 27. Sending messages (2/2) • From Flex • Sending AsyncMessage through the producer • Body: object to send var message:AsyncMessage = new AsyncMessage(); message.body= messageObject; producer.send(message); www.zenika.com
- 28. Receiving message (1/2) public class FlexEventHandler implements EventHandler { @ServiceProperty(name="event.topics") private String eventTopics = ".../amf3/flex/remoting/events/PublishedObjectEvent"; public void handleEvent(Event event) { if (event instanceof PublishedObjectEvent) { ...} } } All Flex messages are received by this handler www.zenika.com
- 29. Receiving message (2/2) • Message: typed-object • Start / cancel subscription private function start():void { consumer.subscribe(); } private function stop():void { consumer.unsubscribe(); } private function onMessage(event:MessageEvent):void { var msg:MyMessage = event.message.body as MyMessage; ... } www.zenika.com
- 30. Some key elements • We have seen how to: • Expose OSGi services to Flex • Interact with different service types • Remote Objects • Event-based messages • Standard web services • Define strongly-typed objects • Handle events posted by the backend www.zenika.com
- 31. Flex modulary • Flex modules • SWF files that can be loaded and unloaded at runtime by an application • Cannot be run independently • Applications can share modules • No need to load all modules at startup www.zenika.com
- 32. Benefits • Split Flex application into several pieces • Smaller initial download size of the SWF • Shorter load time • Better encapsulation • Load required modules only • Unload modules at runtime • Free up memory and resources www.zenika.com
- 33. Main goal • OSGi is the Java modularity • Flex supports modules • How can we build a complete modular application? www.zenika.com
- 34. Creating modules • “Module” as root element <mx:Module xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark" xmlns:mx="library://ns.adobe.com/flex/mx" implements="...api.ModuleInterface" creationComplete="start()"> <fx:Script> <![CDATA[ public function start():void {...} public function stop():void {...} ]]> </fx:Script> <s:Label text="Label" /> </mx:Module> www.zenika.com
- 35. Module lifecycle • Start method is called when the module is loaded • Stop method is called before unloading the module • Common interface between the application and the module package com.zenika.systemmanager.api { public interface ModuleInterface { function stop():void; } } www.zenika.com
- 36. Packaging • Each bundle contains • Business logic • OSGi services Application Module bundle bundle • User interface • SWF file JAVA JAVA • Build may be done with (OSGi) (OSGi) Maven UI UI (SWF) (SWF) www.zenika.com
- 37. Application bundle • User Interface skeleton • Able to retrieve list of available modules • OSGi service for getting module URLs • Flex client notified when a module appears or disappears • Flex consumer is aware of events posted by the EventAdmin www.zenika.com
- 38. Technical view (1/3) • Registers bundle resources into the HTTP Service • Main SWF, HTML files, … • Listens to bundle arrival / departure • Implementation of the extender pattern • Use of a BundeTracker for being notified of bundles declaring Flex modules • MANIFEST.MF : SWF-Modules: [path]=[SWF name] • Register/unregister SWFs into declared path • Post event to notify Flex client www.zenika.com
- 39. Technical view (2/3) var modules:ArrayCollection = event.result as ArrayCollection; for each(var module:SWFModule in modules) { var loader:ModuleLoader = new ModuleLoader(module.url); // Register event listeners loader.addEventListener(ModuleEvent.READY, handleModuleReady); loader.addEventListener(ModuleEvent.ERROR, handleModuleError); // Start the module loading loader.load(); } www.zenika.com
- 40. Technical view (3/3) • After bundle undeployment • Call the stop method • Stop properly on-going processes • Warning: OSGi services have already been unregistered • Unload associated modules • Free-up memory and resources www.zenika.com
- 41. Module bundle • Autonomous module • Contains its own UI and logic • Good isolation • Flex modules can easily be based upon OSGi services www.zenika.com
- 42. Démo DEMO www.zenika.com
- 43. Conclusion (1/2) • Flex • Development of rich interfaces • Native support of modules • Loading / unloading modules at runtime • OSGi • The Dynamic Module System for Java • Service Oriented Architecture • Service availability to Flex www.zenika.com
- 44. Conclusion (2/2) • Seamless communications • Asynchronous remote calls • Notifications • Integration • Application: set of autonomous bundles with their own interface and business logic www.zenika.com