OSGi for Application Developers Neil Bartlett WeigleWilczek UK - - PowerPoint PPT Presentation

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OSGi for Application Developers Neil Bartlett WeigleWilczek UK - - PowerPoint PPT Presentation

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OSGi for Application Developers Neil Bartlett WeigleWilczek UK QCon London 2009 Agenda Brief Intro to OSGi OSGi in Infrastructure The (Partial Failure) of Object Orientation Component Oriented Programming Implementing Components DEMO

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OSGi for Application Developers

Neil Bartlett – WeigleWilczek UK QCon London 2009

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Agenda

Brief Intro to OSGi OSGi in Infrastructure The (Partial Failure) of Object Orientation Component Oriented Programming Implementing Components DEMO

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Brief Intro to OSGi

❶

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OSGi: The Module System for Java

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Standard Java

ABC.JAR

JARs are Deployment Units They are Not Modules

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Meaningful name Version Vendor Exports Dependencies

What’s Missing?

ABC.JAR

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Dependencies

JARs do have dependencies They are implicit. A dependency is an assumption. “I assume module X (version Y) is on the

  • classpath. If not I will crash and burn.”
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Module = “Bundle”

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Meaningful name Version Vendor Exports Dependencies

Just a JAR + Metadata

  • rg.foo.mylib
Manifest-Version: 1.0 Bundle-SymbolicName: com.mylib Bundle-Name: My Library Bundle Bundle-Vendor: Neil Bartlett Bundle-Version: 1.0.0 Import-Package: javax.swing, org.w3c.dom Export-Package: com.mylib1.ui;version=“1.0.0”, com.mylib1.util;version=“1.0.0” Bundle-RequiredExecutionEnvironment: J2SE-1.5
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MANIFEST.MF

Manifest-Version: 1.0 Bundle-SymbolicName: com.mylib Bundle-Name: My Library Bundle Bundle-Vendor: Neil Bartlett Bundle-Version: 1.0.0 Import-Package: javax.swing, org.w3c.dom Export-Package: com.mylib.ui;version=“1.0.0”, com.mylib.util;version=“1.0.0” Bundle-RequiredExecutionEnvironment: J2SE-1.5

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Works Outside OSGi

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Dependency Graphs

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com.foo.bar javax.swing

  • rg.wibble

Imports..... and Exports

com.mylib com.mylib.ui com.mylib.util

} {

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Package Resolution

com.foo.bar

A

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Package Resolution

com.foo.bar

A

com.foo.bar

B

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Package Resolution

com.foo.bar

A

com.foo.bar

B

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Versioned Dependency

com.foo.bar [1.2.0,1.4.0)

A

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Versioned Dependency

com.foo.bar [1.2.0,1.4.0)

A

com.foo.bar 1.4.5

B

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Versioned Dependency

com.foo.bar [1.2.0,1.4.0)

A

com.foo.bar 1.3.12

B’

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Versioned Dependency

com.foo.bar [1.2.0,1.4.0)

A

com.foo.bar 1.3.12

B’

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Side-by-Side Versions

com.foo.bar 1.4.5 com.foo.bar 1.3.12 com.foo.bar [1.2.0,1.4.0) com.foo.bar [1.4.0,1.5.0)

B B’ X Y

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Side-by-Side Versions

com.foo.bar 1.4.5 com.foo.bar 1.3.12 com.foo.bar [1.2.0,1.4.0) com.foo.bar [1.4.0,1.5.0)

B B’ X Y

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How it Works

Bundle-SymbolicName: com.mylib1 Bundle-Version: 1.2.0 Export-Package: com.mylib1.ui;version=“1.2.0”, com.mylib1.util;version=“1.2.0” Bundle-SymbolicName: com.app1 Bundle-Version: 2.2.3.alpha Import-Package: com.mylib1.ui;version=“[1.2.0,1.3.0)” com.mylib1.util;version=“[1.2.0,1.3.0)”

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Private Internals

Exports must be stated explicitly Packages not listed in “Export-Package” are not available to other bundles

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Versions

Standard numbering scheme with well-defined

  • rdering.

major.minor.micro.qualifier First three numeric, last alphanumeric Eg 1.0.0.beta2 Unspecified → 0.0.0

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Version Ranges

Open, closed or implicit [1.0.0, 2.0.0] → 1.0.0 ≤ version ≤ 2.0.0 [1.0.0, 2.0.0) → 1.0.0 ≤ version < 2.0.0 Informally “1.*” 1 → [1.0.0, ∞) Unspecified → [0.0.0, ∞)

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Our Promise*: No More NoClassDefFoundErrors!

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Dynamic! Dynamic!

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Dynamic

Install Bundles Update Bundles Uninstall Bundles ... all “on the fly”

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OSGi for “Infrastructure”

❷

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OSGi: The Standard Module System for Java

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De Facto AND De Jure

de facto: No other module system is more widely used (or is even close) Three independent implementations in open source (EPL, APL and BSD). de jure: JSR 291 (Java SE), JSR 232 (Java ME). OSGi Alliance: Founded 1999, 28 Full Members.

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Just The Full Members

Aplix Corporation Deutsche Telekom Ericsson Mobile Platforms AB GigaSpaces Technologies Harman/Becker Automotive Systems GmbH Hitachi, Ltd. IBM Corporation IONA Technologies LinkedIn Makewave Mitsubishi Electric Corporation Motorola, Inc. NEC Corporation Nokia Corporation NTT Oracle Corporation ProSyst Software GmbH Red Hat Samsung Electronics Co., Ltd. SAP AG Siemens AG Siemens Enterprise Communications Software AG SpringSource Sprint Sun Microsystems, Inc. Telcordia Technologies, Inc. TIBCO Software Inc.

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Where is OSGi Used Today?

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Application Servers

WebSphere WebLogic JBoss GlassFish (JEE RI) Geronimo SAP NetWeaver JOnAS Spring dm Server

NB: SOME ARE PLANNED OR IN-PROGRESS

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ESBs

ServiceMix Mule WS02 Carbon Project Fuji Celtix

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Mobile & Embedded

Too numerous to list (and many are obscure) Just 2 examples: BMW 7-Series cars Sprint Titan platform

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This Is All “Infrastructure”

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Infrastructure ♥ OSGi

Lots of Libraries To Manage Designed for Extensibility Dynamic Deployment, Uptime

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Where are the “Business” Apps?

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The (Partial) Failure of Object Orientation

❸

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Reuse – Harder Than It First Seemed

Image credit: s. bär on Flickr

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“Object Oriented technology was going to change the world... we would have all these objects in our library and building a new system would be a

  • snap. Just get a few classes, bunch

them together... and voila!”

  • Peter Kriens
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What Went Wrong?

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Coupling

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No Man Class Is an Island...

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Classes are Coupled to Other Classes...

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Packages are Coupled to Other Packages...

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Packages are Coupled to JARs...

“CLASSPATH”

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Which are Coupled to More JARs...

“CLASSPATH”

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Which Are Coupled to Yet More JARs...

“CLASSPATH”

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A Solution...?

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Give Up!

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Reuse In Other Contexts is Hard, so...

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Don’t Try!

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Leave Code “In-Place”, and Call Remotely

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...a.k.a. “SOA”

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Component-Oriented Programming

❹

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“COP” Sounds Cooler...

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... Than “OOP”

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Okay Maybe Not...

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OOP Not Broken – Just Not The Whole Answer

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Can We Ever Build Software Like Lego?

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Just What Is a “Component”?

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I Prefer a Different Analogy to Lego Bricks:

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Components

Active players in the system Aware of and adapt to their environment May provide services to other components Have a life cycle

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The “Environment”

“Environment” means: Services provided by other components Resources, devices, etc

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Adaptation

When env is good, the component flourishes When env is harsh, the component survives When very harsh, the component sleeps or dies

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Composable

Components use the services of other components Whole systems can be composed this way

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Loosely Coupled

Components don’t depend on internal details of

  • ther components

Yes, this is the same as OO

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Implementing Components

❺

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Services

Components provide Services Registered with a central Service Registry POJOs! Look-up by Java interface name

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In-Process SOA

Service Provider Service Consumer Service Broker Client Service Register Find Bind Service Contract

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Plain Old Java Objects

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The Glue Between Components

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Dynamics Make Services Slippery

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We Don’t Code Directly to Services

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Let a Framework do the Fiddly Stuff

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Several Frameworks

Declarative Services (DS) Spring-DM Apache iPOJO Peaberry (Guice)

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Perfect Interoperability At Services Level!

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Examining DS

Like a Dependency Injection framework But with dynamic injection... ... and “uninjection”

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DS Component

package org.example.ds; import javax.sql.DataSource; import org.example.osgi.mailbox.api.Mailbox; import org.example.osgi.mailbox.api.MailboxException; import org.example.osgi.mailbox.api.Message; public class DbMailbox implements Mailbox { private DataSource dataSource; protected void setDataSource(DataSource dataSource) { /* ... */ } protected void unsetDataSource(DataSource dataSource) { /* ... */ } @Override public long[] getAllMessages() throws MailboxException { /* ... */ } }

No OSGi Imports JavaBeans Style => Testable

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DS Declaration

<?xml version="1.0" encoding="UTF-8"?> <component name="DbMailbox"> <implementation class="org.example.ds.DbMailbox"/> <service> <provide interface="org.example.mailbox.api.Mailbox"/> </service> <reference name="DataSource" interface="javax.sql.DataSource" bind="setDataSource" unbind="unsetDataSource"/> </component>

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Optional vs Mandatory

<reference name="DataSource" interface="javax.sql.DataSource" bind="setDataSource" unbind="unsetDataSource" policy="static"/> <reference name="Log" interface="org.osgi.service.log.LogService" bind="setLog" unbind="unsetLog" cardinality="0..1"/>

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Lifecycle

protected void activate(Map configuration) { /* ... */ } protected void deactivate() { /* ... */ }

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Dynamic Binding/ Unbinding

<reference name="DataSource" interface="javax.sql.DataSource" bind="setDataSource" unbind="unsetDataSource" policy="static"/> <reference name="Log" interface="org.osgi.service.log.LogService" bind="setLog" unbind="unsetLog" cardinality="0..1" policy="dynamic"/>

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Truly Reusable Components are Thread-Safe

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Thread Safety

private LogService log; protected void setLog(LogService log) { /* ... */ } protected void unsetLog(LogService log) { /* ... */ } protected void activate(Map configuration) { /* ... */ } protected void deactivate() { /* ... */ } @Override public long[] getAllMessages() throws MailboxException { /* ... */ }

Can be called concurrently!

}

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Truly Reusable Components are Stateless

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DEMO

❻

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CONCLUSION

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When is Modularity Not Relevant?

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Getting Involved

OSGi User’s Forum UK just founded. Free for companies and individuals. http://uk.osgiusers.org/

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Getting up to Speed

SkillsMatter Training in April (4 days) http://tinyurl.com/sm-osgi Half price for “1st Teach”

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Getting up to Speed

EclipseCon in 2 weeks! http://www.eclipsecon.org/ 4 tutorials on OSGi (4 hours each) and 15+ sessions Everything you ever wanted to know about OSGi, and then some

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Thank You!

Demo Code: github.com/njbartlett/osgidemo User Forum: uk.osgiusers.org/ Training: tinyurl.com/sm-osgi Me: neilbartlett.name/

OSGi is a trademark or a registered trademark of the OSGi Alliance in the United States, other countries, or both