Dynamic modular Web applications

with Equinox and Vaadin

Kai Tödter Siemens Corporate Technology

Who am I?

Software Architect/Engineer at Siemens Corporate Technology

Eclipse RCP expert and OSGi enthusiast

Open Source advocate

Committer at e4 and Platform UI

E-mail: kai.toedter@siemens.com

Twitter: twitter.com/kaitoedter

Blog: toedter.com/blog

5/9/2011 2 © Kai Tödter and others, Licensed under Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Germany License.

Outline

Demo

Server-side OSGi

Vaadin

Whiteboard Pattern

OSGi Declarative Services (DS)

Code deep dive

Discussion

5/9/2011 3 © Kai Tödter and others, Licensed under Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Germany License.

Demo

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Download & Blog

You can download the demo projects (6,8 MB, including the target platform) at http://www.toedter.com/download/vaadin/osgi-vaadin-demo.zip

See also my blog “Dynamic modular Web Applications with Vaadin and OSGi” http://www.toedter.com/blog/?p=412

5/9/2011 © Kai Tödter and others, Licensed under Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Germany License. 5

Server-side OSGi

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Picture from http://www.sxc.hu/photo/1043923

Server-side OSGi

For this demo I use Equinox as OSGi container

To run server-side Equinox there’s 2 choices:

Embed Equinox in a servlet container

Embed a HTTP server in Equinox

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Embed Equinox in a Servlet Container

Needed bundles:

org.eclipse.equinox.servletbridge

org.eclipse.equinox.servletbridge.http

org.eclipse.equinox.http.servlet

[optional] org.eclipse.equinox.http.registry

See http://www.eclipse.org/equinox/server/ http_in_container.php

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Embed Jetty in Equinox

Needed bundles:

org.eclipse.equinox.http.jetty

org.eclipse.equinox.http.servlet

org.mortbay.jetty

org.apache.commons.logging

javax.servlet

[optional] org.eclipse.equinox.http.registry

See http://www.eclipse.org/equinox/server/ http_in_equinox.php

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Hello, JAX! OSGi Servlet Demo

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Picture by Office Online, iStockPhoto http://office.microsoft.com/en-us/images/results.aspx?qu=world#ai:MP900444203|

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What is Vaadin?

Server-based RIA Framework

Uses Google Web Toolkit (GWT) as rendering engine

Pure Java, no JavaScript, no configuration

Rich widget set

Out of the box OSGi support

Only one JAR file, already an OSGi bundle

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5/9/2011 © Kai Tödter and others, Licensed under Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Germany License. 13

Demo

The Whiteboard Pattern

Problem: Often a service provides an implementation of the publisher/subscriber design pattern and provides methods to register listeners for notifications

The OSGi service model provides a service registry with these notification mechanisms already!

So: Don’t get a service and register as listener

Be a service yourself and register with the OSGi service registry!

14

Example: The Listener Pattern

Clients use ApplicationService to register view and action contributions

Client is responsible for handling dynamic behavior

15

Example: The Whiteboard Pattern

Clients register view and action contributions as services

Application manager is responsible for handling dynamic behavior

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The Action and View contribution managers are NOT services

Instead, they are wrapped in a OSGi Declarative Services (DS) component

All action and view contributions are OSGi services and implement

IActionContribution

IViewContribution

Whiteboard Pattern in Vaadin Demo

17

OSGi Declarative Services

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Component Instance

Component Description

Active Bundle

Component

Component Instance

Component Description

Active Bundle

Component Service

reference

provide

Life Cycle

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Component

DS-powered Bundle

Component Component

Service Component Runtime (SCR)

create

Declaring a Component

Specify component description(s) via Service-Component manifest header

Specify the implementation class

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Service-Component: OSGI-INF/treeView.xml

<component xmlns="http://www.osgi.org/xmlns/scr/v1.1.0">

<implementation class="...TreeView"/>

</component>

Providing a Service

Specify each service interface

By default components providing a service are created on demand (lazy)

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<service>

<provide interface="...IViewContribution"/>

<provide interface="...IActionContribution"/>

</service>

Referencing Services

Specify the service interface

Specify bind and unbind methods

Specify the cardinality

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<reference interface="...IPersonManager"

bind="setPersonManager"

unbind="removePersonManager"

cardinality="1..1"/>

Further Reading

Chris Brind: In Bed with Vaadin and OSGi http://www.perplentropy.com/2010/02/in-bed-with-

vaadin-and-osgi.html I use Chris’ bundles in this demo

Neil Bartlett: Vaadin OSGi bridge at GitHub https://github.com/njbartlett/VaadinOSGi

Petter Holmström: Creating a Modular Vaadin Application with OSGi http://vaadin.com/wiki/-

/wiki/Main/Creating%20a%20Modular%20Vaadin%20Application%20with%20OSGi

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Putting it all together…

Main demo application is a DS component

factory='vaadin.app' => used Chris Brind’s implementation

0..n service references to

IViewContribution

IActionContribution

Source code will be shown soon…

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Resources, Images and Themes

Resources (e.g. images) have to be put in a fragment with the com.vaadin bundle as host

See project com.siemens.ct.osgi.vaadin.pm.theme

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Code Deep Dive

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Picture from http://www.sxc.hu/photo/1159613

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Picture from http://www.sxc.hu/photo/922004

License

This work is licensed under the Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Germany License

See http://creativecommons.org/licenses/by-nc-nd/3.0/de/deed.en_US

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Picture Index

Slide „Server-side OSGi“: http://www.sxc.hu/photo/1043923

Slide „Hello JAX!“: http://office.microsoft.com/en-us/images/results.aspx?qu=world#ai:MP900444203|

Slide „Reindeer“ Animation: http://www.sxc.hu/photo/1138596

Slide „Code Browsing“: http://www.sxc.hu/photo/1159613

Slide “Discussion”: http://www.sxc.hu/photo/922004

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Many thanks to the authors of the following pictures: