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OSGi and Java EE: A Hybrid Approach to Enterprise Java Application Development

Sanjeeb Sahoo

Staff Engineer, Sun Microsystems India Pvt. Ltd.

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The following is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions.The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle.

Safe Harbor Statements

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The preceding is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions.The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle.

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Agenda

• OSGi 101• OSGi meets Java EE – Hybrid Applications• Advanced usecases• Hybrid Application Demo• Q & A

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Agenda

• OSGi 101• OSGi meets Java EE – Hybrid Applications• Advanced usecases• Hybrid Application Demo• Q & A

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OSGi

Service oriented dynamic

module system for Java

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OSGi Layers

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Module Layer

• Bundle – a unit of modularity in OSGi• Encapsulation• Lifecycle independent of the JVM• Versionable• Packaged as a JAR (classes + Manifest with OSGi

metadata)• Very explicit dependency specification• Well defined dependency resolution rules

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Bundle-SymbolicName: com.acme.hello.startup

Bundle-Name: Hello World OSGi Sample

Bundle-Version: 1.0.1

Bundle-ManifestVersion: 2

Bundle-Activator: com.acme.hello.startup.MyActivator

Export-Package: com.acme.hello.startup;version=1.0.0

Import-Package: org.osgi.framework;version=1.3

OSGi Metadata

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Classloading in OSGi

Image from the OSGi R4 Core Specification

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Lifecycle Layer

• Provides an API to manage bundles– BundleContext.install– BundleContext.uninstall– Bundle.update

• BundleActivator• BundleListener – listen to BundleEvents

– Synchronous– Asynchronous

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Bundle Lifecycle

Image from the OSGi R4 Core Specification

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Service Layer

• In-VM SOA• Service Registry

– Register – Unregister

• Service is a POJO• Service Dynamism

– Service tracking

• Service Discovery– LDAP filter based queries

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Interactions between OSGi Layers

Image from the OSGi R4 Core Specification

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OSGi benefits – a recap

• Layered approach

• Modularity– Enforces modularity

– Ensures class-space consistency

– Enables component reuse

– Supports versioning and evolution

• Dynamism– Bundles

– Services

• Ease of deployment and management– OBR

• Bundle deployment order is not relevant

– Faster deployment cycle

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OSGi meets Java EE

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Agenda

• OSGi 101• OSGi meets Java EE – Hybrid Applications• Advanced usecases• Hybrid Application Demo• Q & A

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Java EEPlatform of choice for enterprise applications

• Widely used APIs (JPA, JTA, JAXB, JNDI)• Component Models (Servlet, EJB, JAX-RS)• Frameworks (JSF, CDI)• Ease of Use (Annotations, Convention over

Configuration)• Platform provided infrastructure services

(Transaction, Security, Persistence, Remoting)• Tools (IDE, Management, Monitoring)• Ubiquitous deployment platform for enterprise

applications

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Hybrid ApplicationsMeeting of the two worlds

• OSGi + Java EE = Hybrid application• Hybrid application

– An OSGi bundle– And a Java EE Archive

• Leverage the capabilities of both the platforms– Enterprise applications can now

• be built as modular OSGi bundles• use OBR, Config Admin, service tracking, etc.

– OSGi bundles can now use Java EE services like JTA, JPA, etc.

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Current State

• OSGi Enterprise Expert Group (EEG)– Relased OSGi Service Platform Enterprise Specification 4.2

in 2010

• Open source efforts– Project GlassFish– Project Aries– Eclipse Gemini

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OSGi/Web Application (WAB)

• Web Application Bundle (WAB)– WAR + OSGi metadata + Web-ContextPath header

• Can use all enterprise APIs (like JPA, JTA)• Wrapped WAR support

– webbundle: URL scheme

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Bundle-SymbolicName: com.acme.hellowab

Bundle-Name: Hello World OSGi Web Application

Bundle-Version: 1.0.0

Bundle-ManifestVersion: 2

Bundle-Activator: com.acme.hellowab.MyActivator

Import-Package: javax.servlet; javax.servlet.http; version=3.0,

org.osgi.framework; version=1.5

Bundle-ClassPath: WEB-INF/classes, WEB-INF/lib/foo.jar

Web-ContextPath: /hello

OSGi Metadata of a WAB

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Hybrid application bundle lifecycle

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Enterprise OSGi Specifications

• OSGi/Web Application• OSGi/JPA• OSGi/JDBC• OSGi/JTA• OSGi/JNDI• OSGi/HTTP Service• OSGi Blueprint Service

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EE APIs in OSGi

• OSGi/JDBC– JDBC driver as DataSourceFactory– Dynamic discovery of driver details– Multiple versions of same driver

• OSGi/JTA– JTA artifacts available as OSGi Services

• OSGi/JPA– Enhancement of JPA entities at runtime– Same packaging rules as JPA and also deploy entities as a

bundle– Shared Persistence Unit and thereby shared second level

cache

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Tools

• BND (http://www.aqute.biz/Code/Bnd)– de-facto tool for OSGi metadata generation– maven-bundle-plugin– Ant task

• IDE– Eclipse– NetBeans– IntelliJ IDEA

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Advanced Usecases

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<Insert Picture Here>

Agenda

• OSGi 101• OSGi meets Java EE – Hybrid Applications• Advanced usecases• Hybrid Application Demo• Q & A

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OSGi/EJB Application

• Allows you to develop managed, transactional, secure OSGi services with very little knowledge of OSGi

• Make your existing EJB service available to OSGi clients with little effort

• Achieved through simple manifest metadata– Export-EJB: ALL/None/<names of stateless local EJB>

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Bundle-SymbolicName: com.acme.helloEjbOsgi

Bundle-Name: Hello World OSGi EJB Bundle

Bundle-Version: 1.0.0

Bundle-ManifestVersion: 2

Import-Package: javax.ejb; version=3.0,

Export-EJB: ALL

OSGi Metadata of an OSGi/EJB bundle

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CDI

• Brings type-safe dependency injection to EE platform– Strong typing and loose coupling

• Well defined life cycle of stateful objects bound to life cycle contexts

• Ability to decorate and intercept injected Beans• An event notification model• An ability to develop portable extensions that

integrates with the container to extend the runtime

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GlassFish CDI/OSGi Portable Extension

• Use of CDI for type safe injection of OSGi services

@WebServlet(urlPatterns = “/login”)

public class FooServlet implements HttpServlet {

    @Inject 

    @org.glassfish.osgicdi.OSGiService(

          dynamic=”true”, 

          timeout = 200, 

          serviceCriteria=<an ldap query >)

    FooService foo;

}

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Demo: Putting them together

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Demo schematic

• WAB

• JPA- LAZY loading

• EJB as Service

• OSGi Service Injection

• OBR

• Security/Transaction

Context propagation

Simple

OSGi

Bundle

OSGi

Service

Simple

OSGi

Service

EJB

OSGi

Service

Advanced

WAB

Simple

WAB

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Call To Action

• Want to build hybrid applications? – Try our tutorial at http://tinyurl.com/osgieehol

• Want to try out?– Use GlassFish 3.1 trunk builds from http://glassfish.org

• Questions?– users@glassfish.dev.java.net

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References

• OSGi Service Platform Core and Enterprise Specification 4.2 – http://www.osgi.org

• Project GlassFish – http://glassfish.org

• Hybrid application samples– http://wikis.sun.com/display/GlassFish/BlogsGfOsgi

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<Insert Picture Here>

Agenda

• OSGi 101• OSGi meets Java EE – Hybrid Applications• Advanced usecases• Hybrid Application Demo• Q & A

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<Insert Picture Here>

OSGi and Java EE: A Hybrid Approach to Enterprise Java Application Development

Sanjeeb Sahoo

Staff Engineer, Sun Microsystems India Pvt. Ltd.