Osgi platform

OSGi platform

Yuriy ShapovalovEPAM Systems

What is it?

“The Open Services Gateway initiative framework is a module system and service platform for the Java programming language that implements a complete and dynamic component model, something that as of 2012 does not exist in standalone Java/VM environments.” – Wikipedia

OSGi Platform

… module system …


OSGi Platform

… service platform …


OSGi Platform

… for Java programming language …


OSGi Platform

…complete and dynamic component model …


OSGi Platform


OSGi Platform

… does not exist in standalone Java/VM …

OSGi history

o Initially was developed as an embedded platform for the “home gateway”;o and make it easier to deploy Java application on embedded devices

o OSGi Alliance was formed in 1999, and it has following mission:• Maintaining and publishing OSGi specification• Certifying implementations• Organizing events.

o Specification target was: “Define Java-based service platform, full dynamic component model”• Because JVM does not support natively dynamic module

system – starting, stopping, updating application at runtime• JAR dependencies management missing

OSGi Platform 8/42

o Adaptive

o Flexible

o Contracts

o Robust

o Secure

o Evolution

o Distributed

The Dream

OSGi Platform 9/42

B C

D E F

G H I

Adaptive

o Flexible

o Contracts

o Robust

o Secure

o Evolution

o Distributed

The Dream

OSGi Platform 10/42

A B C

D E F

G H I

Adaptive

o Flexible

o Contracts

o Robust

o Secure

o Evolution

o Distributed

The Dream

OSGi Platform 11/42

A B C

D E F

G H I

Adaptive

Flexible

o Contracts

o Robust

o Secure

o Evolution

o Distributed

The Dream

OSGi Platform 12/42

A Ba C

D E F

G H I

Bb

Adaptive

Flexible

o Contracts

o Robust

o Secure

o Evolution

o Distributed

The Dream

OSGi Platform 13/42

A Ba C

D E F

G H I

Bb

Adaptive

Flexible

Contracts

o Robust

o Secure

o Evolution

o Distributed

The Dream

OSGi Platform 14/42

A Ba C

D E F

G H I

Bb

Adaptive

Flexible

Contracts

o Robust

o Secure

o Evolution

o Distributed

The Dream

OSGi Platform 15/42

A Ba C

D E F

G H I

Bb

Adaptive

Flexible

Contracts

Robust

o Secure

o Evolution

o Distributed

The Dream

OSGi Platform 16/42

A Ba C

D E F

G H

Bb

Adaptive

Flexible

Contracts

Robust

o Secure

o Evolution

o Distributed

The Dream

OSGi Platform 17/42

A Ba C

D E F

G H

Bb

Adaptive

Flexible

Contracts

Robust

Secure

o Evolution

o Distributed

The Dream

OSGi Platform 18/42

A Ba C

D E F

G H

Bb

Adaptive

Flexible

Contracts

Robust

Secure

o Evolution

o Distributed

The Dream

OSGi Platform 19/42

A Ba C

D E F

G H

Bb

Adaptive

Flexible

Contracts

Robust

Secure

o Evolution

o Distributed

The Dream

OSGi Platform 20/42

A Ba C

D E F

G H I v2.0

Bb

Adaptive

Flexible

Contracts

Robust

Secure

Evolution

o Distributed

The Dream

OSGi Platform 21/42

A Ba C

D E F

G H I v2.0

Bb

Adaptive

Flexible

Contracts

Robust

Secure

Evolution

o Distributed

The Dream

OSGi Platform 22/42

A Ba C

D E F

G H I v2.0

Bb

Adaptive

Flexible

Contracts

Robust

Secure

Evolution

Distributed

The Dream

OSGi Platform 23/42

A Ba

D E F

G I v2.0

Bb

What is an OSGi application

o Collection of bundles integrated via Service interfaceso Bundles may be independently developed and deployedo Bundles and their associated services may appear or

disappear at any time

o Resulting application follows a Service-Oriented Component Model approacho Combines Ideas from both component and service orientation

OSGi Platform 24/42

Architecture abstraction

o Application is a set of independent components, collaborating between each other in a service orienting way.

OSGi Platform 25/42

Application

A C D

B E F


o Application implement reduced functionality, all additional features implements as plug-ins

OSGi Platform 26/42

ApplicationA

C

D

B E F


o or even…

OSGi Platform 27/42

Application

A C D

B E

A

B

D

E

× Focus on “what”, not “how”× Encapsulate the implementation details× Formalize the input data (arguments)× Formalize the output data (return values)

Next level of modularity

OSGi Platform 28/42

Subroutines (50’s)

Then systems grew…

Spaghetti Code


OSGi Platform 29/42


Functions

functionInput (arguments) Output (return)


OSGi Platform 30/42


Functions

Modules (70’s)

ModuleImported Functions Exported Functions


Sharing Proved Hard


OSGi Platform 31/42


Functions

Classes/Objects (80’s)

Modules (70’s)

TypeImported Members Exported Members



OSGi Platform 32/42


Functions


Modules (70’s)

Packages (90’s)

TypeImported Types Exported Types

Then systems grew…… and distributed… and multiplies

Small Java App …


OSGi Platform 33/42


OSGi Platform 34/42


Functions


Modules (70’s)

Packages (90’s)

Bundles (00’s)

Bundle(JAR file)

Imported Packages Exported Packages

Bundle

o A Bundle - is a module in OSGi terminology

o What is a bundle?• Simply a JAR file plus module metadata• Modules metadata is stored in META-INF/MANIFEST.MF

• Define what the module provides and require

o What does a bundle JAR contain?• Java classes (i.e., standard JAR file content)• Resources (e.g., configuration files, images, etc.)• Native code• Embedded JAR files

• Bundles have their own class path

OSGi Platform 35/42

OSGi architecture

OSGi Platform 36/42

OS / Hardware

Java VM

OSGi LayerApplication composite(Bundles)

Security

Module

Life Cycle

Service

BundleBundle

BundleBundle

BundleBundle

Bundle

Life cycle of bundles

OSGi Platform 37/42

INSTALLED

RESOLVED

UNINSTALLED

STARTING

ACTIVE

STOPPING

Services System

o Services are simple POJOs with a published service interfaceo Coupling to the framework is isolated to the Activator and

collaboratorso Services may bind to other services through their published

interfaceso The framework provides a standard Service Factory mechanism

OSGi Platform 38/42

Bundle A Service Registry

Bundle B

Bundle C

Service

publish

track

track

publish

OSGi Bundle Manifest

OSGi Platform 39/42

Bundle-ManifestVersion: 2

Bundle-SymbolicName: org.foo.simplebundle

Bundle-Version: 1.0.0

Bundle-Activator: org.foo.Activator

Bundle-ClassPath: .,org/foo/embedded.jar

Bundle-NativeCode: libfoo.so; osname=Linux; processor=x86,foo.dll; osname=Windows 7; processor=x86

Import-Package:o sgi.service.log; version="[1.0.0,1.1.0)"; resolution:="optional"

Export-Package: org.foo.service; version=1.1; vendor="org.foo:"; exclude:="*Impl", org.foo.service.bar; version=1.1; uses:="org.foo.service"


OSGi Platform 40/42









Indicates semantic and syntax


OSGi Platform 41/42









Indicates semantic and syntaxGlobally unique ID


OSGi Platform 42/42









Life cycle entry point


OSGi Platform 43/42









Internal bundle class path


OSGi Platform 44/42









Native code dependencies


OSGi Platform 45/42







Import-Package: osgi.service.log; version="[1.0.0,1.1.0)"; resolution:="optional"


Optional dependency on a package version

range


OSGi Platform 46/42









Provided package with arbitrary attribute and

excluded classes


OSGi Platform 47/42









Provided package with dependency on

exported package

Declarative Services

o Declarative services provides a minimally intrusive way to:• Define components that provide and use services• Automate dependency resolution and maintenance

OSGi Platform 48/42

package foo.impl;public class HelloImpl implements foo.HelloService { LogService log; protected void setLog(LogService l) { log = l; } protected void unsetLog(LogService l) { log = null; } public void sayHello(String s) { log.log(LogService.LOG_INFO, "Hello " + s); }}

Declarative Services

o Declarative services component metadata:

OSGi Platform 49/42

<?xml version="1.0" encoding="UTF-8"?><component name="example.hello"> <implementation class="foo.impl.HelloImpl"/> <service> <provide interface="foo.HelloService"/> </service> <reference name="LOG" interface="org.osgi.service.log.LogService" bind="setLog" unbind="unsetLog" /></component>

OSGi implementations

o Specification it is good, but without implementation it is a dead stuff

o The most popular open source implementation is:

• Equinox

• Apache Felix

• Knopflerfish

OSGi Platform 50/42

OSGi in Enterprise (as example)

o Why?• Create modular and reusable software• Create evolvable software• Create line of products

o What?• Desktop Applications• Web Applications• Service Layers• Content Management Systems• Embedded and Mobile Applications• Cloud Applications

OSGi Platform 51/42

Conclusions

o Java needs improved modularity support• Lagging behind .NET in this area for years• The OSGi framework provides it now

o Importance and relevance of OSGi is growing• Industry support for mobile applications• Significant uptake in the enterprise space

OSGi Platform 52/42

Questions?

OSGi Platform 53/42

Osgi platform

Technology

home gateway o

osgi history o

deployed o bundles

o specification target

service interfaces o

wikipediaosgi platform

dynamic component model

javabased service platform