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Introduction to OSGiMarcel Offermans

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Introduction

• Marcel Offermans

• marcel.offermans@luminis.nl

• Luminis

• IT solutions from idea toimplementation

• with and for customers:consultancy and projects

• experts in Java, OSGi, .NET,Agile/Scrum

• Apache Felix and Ace PMC

Enschede

image © 2008 Google Earth

ApeldoornArnhem

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Agenda

• History of OSGi

• The Framework

• The Compendium

• Patterns, Models & Embedding

• Open Source Frameworks

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OSGi history

• Started as an embedded platform for the “home gateway”

• Originally under the JCP as JSR-8 (1999)

• OSGi alliance, consists of a large number of big companies, with the following mission:

• Maintaining and publicizing the OSGi specification.

• Certifying implementations.

• Organising events.

• Current version: OSGi Release 4.1 (JSR-291)

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OSGi releases

• R1: may 2000

• R2: october 2001

• Java Embedded Server (Sun), Oscar (SourceForge)

• R3: march 2003

• Knopflerfish

• R4: august 2005

• IBM joined and influenced this release, Equinox (Eclipse Foundation)

• R4.1: april 2007

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OSGi today

OSGi technology is the dynamic module system for Java™

OSGi technology is Universal Middleware.

OSGi technology provides a service-oriented, component-based environment for developers and offers standardized ways to manage the software lifecycle. These capabilities greatly increase the value of a wide range of computers and devices that use the Java™ platform.

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OSGi Alliance

• Expert Groups:

• core platform (CPEG)

• mobile (MEG)

• vehicle (VEG)

• enterprise (EEG)

• residential (REG)

• Working Groups:

• marketing

• requirements

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OSGi specification

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OSGi Alliance

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Signatu re Not Verified

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OSGi Alliance

Digitally signed by OSGi Alliance DN: cn=OSGi Alliance, c=US Date: 2007.02.22 14:45:47 + 01'00'

Signatur e Not Verified

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OSGi Framework Layering

L3 - Provides a publish/find/bind service model to decouple bundles

L2 - Manages the life cycle of a bundle in a framework without requiring the vm to be restarted

L1 - Creates the concept of a module (aka. bundles) that use classes from each other in a controlled way according to system and bundle constraints

L0 - well defined profiles that define the environment in which bundles can work, ie:* CDC/Foundation* JavaSE-6

SERVICE MODEL

MODULE

LIFE-CYCLE

ExecutionEnvironment

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Module Layer (1/3)

• Unit of deploymentis the bundle i.e., a JAR

• Separate class loaderper bundle

• Class loader graph

• Independent namespaces

• Class sharing at the Java package level

Module

ModuleBundle Bundle Bundle

org.apache.utils 1.0

org.apache.utils 1.1org.apache.log 2.3

org.apache.db 1.4

Bundle

exports

imports

exports

imports

exports

exports

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Module Layer (2/3)

• Multi-version support

• i.e., side-by-side versions

• Explicit code boundaries and dependencies

• i.e., package imports and exports

• Support for various sharing policies

• i.e., arbitrary version range support

• Arbitrary export/import attributes

• Influence package selection Module

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Module Layer (3/3)

• Sophisticated class space consistency model

• Ensures code constraints are not violated

• Package filtering for fine-grained class visibility

• Exporters may include/exclude specific classes from exported package

• Bundle fragments

• A single logical module in multiple physical bundles

• Bundle dependencies

• Allows for tight coupling when required Module

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Manifest

Bundle-Name: Example BundleBundle-SymbolicName: net.luminis.example.bundleBundle-Version: 1.0.0DynamicImport-Package: net.luminis.jdbc.*Import-Package: org.osgi.framework;version=“1.3“, org.osgi.service.event;version=“[1.1,2.0)“, net.luminis.foo;resolution:=“optional“Export-Package: org.osgi.service.event;uses:=org.osgi.framework;version=“1.1“Bundle-ManifestVersion: 2

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Life-cycle Layer

• Managed life cycle

• States for each bundle;

• Allows updates of existing bundles

• Dynamically install, start, update, and uninstall

Life-cycle

Life-cycle

start

end

installedinstall

startingstart

stopping stop

activeresolved

uninstalled

uninstall

Module

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Life-cycle Example

Bundle

OSGi Framework

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Life-cycle Example

Bundle

OSGi Framework

Provided Package

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Life-cycle Example

Bundle

OSGi Framework

Bundle

Install

Bundle

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Life-cycle Example

Bundle

OSGi Framework

Bundle

Resolve

Bundle

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Service Layer

• OSGi framework promotes service oriented interaction pattern among bundles

Service

Service

Log Database

Bundle Bundle Bundle

publish useuse

publish

Bundle

Prefs

publish

use

Service Provider

Service Requester

Service Registry

interact

publish find

Life-cycle

Module

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Service Example

Bundle

OSGi Framework

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Service Example

Bundle

OSGi Framework

Provided Package

Provided Service

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Service Example

Bundle

OSGi Framework

Bundle

Install

Bundle

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Service Example

Bundle

OSGi Framework

Bundle

Resolve

Bundle

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Service Example

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Security Concepts Overview

• Codebased security of the Java Security Model

• Makes use of Protection Domain

• The stack walk based Permission Check

• Signed bundles

• User based security is supported by the UserAdmin service but not integrated in the standard permission check as with JAAS

• PermissionAdmin and ConditionalPermissionAdmin servicesprovide management infrastructure

Security

Module

Life-cycle

Service

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Conditional Permission Admin

• New (4.0) way of doing permission management

• use this exclusively for new implementations

• interoperability when both PA and CPA are present

• IF all conditions of a set of conditions match THEN apply the supplied permissions

• More flexible, extensible model

• Conditions evaluation is highly optimized

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Example

ConditionalPermissionAdmin condPermAdmin = getConditionalPermissionAdmin();

condPermAdmin.addConditionalPermissionInfo( new ConditionInfo[] { new ConditionInfo( BundleLocationCondition.class.getName(), new String[] {"*://www.luminis.nl/*"}) }, new PermissionInfo[] { new PermissionInfo(AdminPermission.class.getName(), "*", "*"), new PermissionInfo(ServicePermission.class.getName(), "*", ServicePermission.GET), new PermissionInfo(ServicePermission.class.getName(), "net.luminis.service.*", ServicePermission.REGISTER), new PermissionInfo(PackagePermission.class.getName(), "net.luminis.service.*", PackagePermission.EXPORT), new PermissionInfo(PropertyPermission.class.getName(), "*", "read") });

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Signing bundles in Eclipse

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BundleSignerCondition

• Condition to test if the signer of a bundle matches a pattern

• Uses the wildcard matching

condPermAdmin.addConditionalPermissionInfo(new ConditionInfo[]{ new ConditionInfo(BundleSignerCondition.class.getName(),

new String[]{"*,o=luminis"}) }, ALLPERMISSION_INFO);

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Local Permissions

• Defined in a resource inside the bundle

• Defines a set of permissions that are enforced by the framework

• A bundle can get less than these permissions, but never more

• Defaults to All Permissions

• Good way for operators to “audit” the permissions of a bundle

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Local Permissions Example

• OSGI-INF/permissions.perm

( ..ServicePermission "..log.LogService" "GET" ) ( ..PackagePermission "..log" "IMPORT" ) ( ..ServicePermission "..cm.ManagedService" "REGISTER" )( ..PackagePermission "..cm" "IMPORT" ) ( ..ServicePermission "..useradmin.UserAdmin" "GET" ) ( ..PackagePermission "..cm" "SET" ) ( ..PackagePermission "com.acme.chess" "IMPORT,EXPORT" ) ( ..PackagePermission "com.acme.score" "IMPORT" )

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Agenda

• History of OSGi

• The Framework

• The Compendium

• Patterns, Models & Embedding

• Open Source Frameworks

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OSGi compendium

Log

HTTP

Device Access

Configuration AdminPreferences

Metatype

Wire AdminUser Admin

IO Connector

Initial Provisioning

UPnP™ Device

Declarative Services

Event Admin Service Tracker

XML Parser

Position

Measurement and State

Execution Environment Spec

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OSGi Alliance

Digitally signed by OSGi Alliance DN: cn=OSGi Alliance, c=US Date: 2007.02.22 14:44:10 + 01'00'

Signatu re Not Verified

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User Admin

• Used in any application that needs role based access control

• Provides: users, roles and groups

• Can authenticate users

• Can determine autorization for authenticated users

• Fairly easy to plug-in to HTTP, SOAP, RMI, JMX or anything else

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Config Admin

• Configuration Admin:

• contains externally configurable settings for a service;

• allows manage-ment systems to configure all settings;

• settings can becreated even before theactual bundle is installed.

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Event Admin

• Publish subscribe

• Asynchronous and synchronous

• Hierarchical topics

• Used within OSGi too

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Event AdminExample

class Subscriber implements BundleActivator, EventHandler { final static String[] topics = new String[] { "org/osgi/service/log/LogEntry/LOG_WARNING", "org/osgi/service/log/LogEntry/LOG_ERROR" };

public void start(BundleContext context) { Dictionary d = new Hashtable(); d.put(EventConstants.EVENT_TOPIC, topics); d.put(EventConstants.EVENT_FILTER, "(bundle.symbolicName=com.acme.*)"); context.registerService(EventHandler.class.getName(), this, d); } public void stop(BundleContext context) { }

public void handleEvent(Event event) { //... }}

class Publisher { EventAdmin m_eventAdmin;

public void send() { if (m_eventAdmin != null) { Dictionary properties = new Hashtable(); properties.put("timestamp", new Date()); m_eventAdmin.sendEvent(new Event("com/acme/timer", properties)); } }}

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Preferences

• Preferences:

• contains bundle privatesettings;

• is coupled to the bundlelife-cycle;

• like the standard Java APIthere is a notion of systemand user preferences perbundle.

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Agenda

• History of OSGi

• The Framework

• The Compendium

• Patterns, Models & Embedding

• Open Source Frameworks

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Service Whiteboard Pattern

• Instead of having clients look up and use a service interface, have clients register a service interface to express their interest

• The service tracks the registered client interfaces and calls them when appropriate

• This is called the Whiteboard pattern

• It can be considered an Inversion of Control pattern

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Service vs. Extender Models

• Two different approaches for adding extensibility to an OSGi-based application

• The service-based approach uses the OSGi service concept and the service registry as the extensibility mechanism

• The extender-based approach uses the OSGi installed bundle set as the extensibility mechanism

• Advantages and disadvantages for each

• Can be used independently or together

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Example code

http://felix.apache.org/site/apache-felix-application-demonstration.html

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Bundled vs. Hosted

• Applications can leverage OSGi functionality in two ways

• Bundled application

• Build entire application as a set of bundles that will run on top of a framework instance

• Hosted framework

• Host a framework instance inside the application and externally interact with bundles/services

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Hosted Framework

• More complicated due to external/internal gap between application and framework

• e.g., unlike bundles the host application does not have a bundle context by which it can access framework services

• Requires host/framework interactions

• Accessing framework

• Providing services to bundles

• Using services from bundles

• Standardized API is in progress for R4.2

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Hosted Framework

• Felix tries to simplify hosted framework scenarios

• Configuration data is passed into framework constructor

• Felix framework is the System Bundle

• Gives the host application an intuitive way to access framework functionality

• Felix constructor also accepts „constructor activators“ to extend system bundle

• Felix tries to multiplex singleton resources to allow for multiple framework instances

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Hosted Framework

public class Main { private static Felix m_felix = null; public static void main(String[] args) throws Exception { Map configMap = new HashMap(); configMap.put(AutoActivator.AUTO_START_PROP + ".1", "file:bundle/org.apache.felix.shell-1.0.2.jar " + "file:bundle/org.apache.felix.shell.tui-1.0.2.jar"); List list = new ArrayList(); list.add(new AutoActivator(configMap)); configMap.put(FelixConstants.SYSTEMBUNDLE_ACTIVATORS_PROP, list); try { m_felix = new Felix(configMap); m_felix.start(); m_felix.waitForStop(); System.exit(0); } catch (Exception ex) { System.err.println("Could not create framework: " + ex); ex.printStackTrace(); System.exit(-1); } }}

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Hosted Framework

• Providing a host application service:

• Accessing internal bundle services:

BundleContext bc = felix.getBundleContext();bc.registerService(Service.class, svcObj, null);

BundleContext bc = felix.getBundleContext();ServiceReference ref = bc.getServiceReference(Service.class);Service svcObj = (Service) bc.getService(ref);

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Hosted Framework

• Classes shared among host application and bundles must be on the application class path

• Disadvantage of hosted framework approach, which limits dynamics

• Use of reflection by host to access bundle services can eliminate this issue, but it is still not an optimal solution

• In summary, better to completely bundle your application if possible

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Open Source Implementations

• Apache Felix: http://felix.apache.org/

• R4, originally called Oscar

• Knopflerfish 2: http://www.knopflerfish.org/

• R4, open source version of UbiServ by Makewave

• Equinox: http://www.eclipse.org/equinox/

• R4, initially developed for Eclipse and the RCP

• Concierge: http://concierge.sourceforge.net/

• R3, optimized for resource constrained environments

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Agenda

• History of OSGi

• The Framework

• The Compendium

• Patterns, Models & Embedding

• Open Source Frameworks

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Coming soon:

• software distribution

• configuration management

• just started in the Apache Incubator

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Any questions?

? & !