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Slide 1 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Using OSGi to Build Better Software Lessons from a Telemedicine Software for Smartphones and Desktop Systems Doreen Seider (DLR - German Aerospace Center) ApacheCon NA 2011 (Vancouver, 11/11/2011)
Slide 2 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Outline
What software did we want to have? How did we develop it with OSGi? What did we learn?
What kind of software did we want to have?
ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
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Slide 5 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Telemonitoring Software
Supports remote monitoring of patients (e.g. in rural areas) Captures vital sign of patients from medical devices Sends measurements to doctors sitting in a medical service center Executable on mobile devices and desktop systems Supports any kind of medical device and medical service center
Slide 8 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
In Comparison to That: Flexible Telemonitoring Software
Slide 9 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Flexible Telemonitoring Software Technology
Plug&Care Connector
Slide 10 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Plug&Care Connector Requirements
1. Both on smartphones (like Android or Windows Mobile) and on desktop system executable
2. Support of any device and service center – even later on – without modification of the Plug&Care Connector
How did we develop it with OSGi?
ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
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Slide 12 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Plug&Care Connector‘s Architecture
Slide 13 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
OSGi Principles: Bundles and Services
OSGi is specification of a modular service platform written in Java „modular“
It is a module layer above the Java package layer Classes are assembled to packages packages are assembled to bundles (modules) bundles are assembled to applications
Slide 14 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
OSGi Principles: Bundles and Services
By default bundles are totally encapsulated Bundles can make use of each other by explicit exports and imports of packages
Slide 15 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
OSGi Principles: Bundles and Services
OSGi is specification of a modular service platform written in Java „service“
In a perfect world bundles make use of each other via services Eliminates direct dependencies to each others implementation
Slide 16 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
OSGi Principles: Bundles and Services
Slide 17 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
OSGi Principles: Bundles and Services
Service definition and implementation are separated to each other No direct implementation dependencies Enables loose coupling Important for assembling bundles (jars) to applications
Slide 18 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
OSGi Principles: Bundles and Services
Slide 19 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
OSGi Principles: Declarative Services (DS)
OSGi Runtime calls the bundle and not other way around
Slide 20 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
OSGi Principles: Declarative Services (DS)
Bundles provide a set of so called component descriptions A component is a Java class Each describes which services a component provides and consumes OSGi runtime injects all required services at start up
Slide 21 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
OSGi Principles: Declarative Services (DS)
Benefits of Declarative Services Less complexity in own code Better testing (no mock up of OSGi runtime needed)
Slide 22 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Fulfilling Requirements with the help of OSGi
1. Both on smartphones (like Android or Windows Mobile) and on desktop system executable
Platform independency by realizating it as OSGi application OSGi serves as an abstraction layer of underlying diversity Using different implementations of OSGi for different platforms Assembling bundles to the Plug&Care Connector application according to its deployment platform
Slide 23 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Used OSGi Implementations: Equinox
For desktop Eclipse Software Foundation OSGi implementation under Eclipse Decision was made due to experiences from other software we develop
Slide 24 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Used OSGi Implementations: mBS Mobile
For Smartphones ProSyst company (http://prosyst.com) Android, Windows Mobile, Nokia S60 http://dz.prosyst.com/mbsmobile/ Decision was made due to supported platforms at that time and due to development status
Slide 25 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Used OSGi Implementations: mBS Mobile Integration in Android
Slide 26 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Used OSGi Implementations: mBS Mobile OSGi Management on Android
Slide 27 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Used OSGi Implementations: mBS Mobile OSGi Applications on Android
Slide 28 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
OSGi-Stack: mBS Mobile Development Environment in Eclipse
Slide 29 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
OSGi-Stack: mBS Mobile Development Environment in Eclipse
Slide 30 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Designing Plug&Care Connector Abstraction with the use of Console
OSGi comes with a console for management purposes It is useful for testing i.e. interacting with the application if no GUI is available yet Own commands can be provided Different OSGi implementations might have different console APIs Abstraction of console APIs is needed to hide them for the underlying application layers writing to the console
Slide 31 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Designing Plug&Care Connector Abstraction with the use of Console
Layered architecture of affected bundles
Slide 32 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Designing Plug&Care Connector Abstraction with the use of Device Communication
Measurements are captured via Bluetooth There are different bluetooth implementations on different devices Later on not only Bluetooth, but USB should be supported as well Abstraction of communication layer and Bluetooth implementations is needed to ensure driver implemenentation must not be changed
Slide 33 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Designing Plug&Care Connector Abstraction with the use of Device Communication
Layered architecture of affected bundles
Slide 34 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Designing Plug&Care Connector Abstraction with the use of Console and Device Communication
Deployment
Slide 35 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Fulfilling Requirements with the help of OSGi
1. Both on smartphones (like Android or Windows Mobile) and on desktop system executable
Platform independency by realizating it as OSGi application OSGi serves as an abstraction layer of underlying diversity Using different implementations for different platforms
2. Support of any device and service center – even later on – without
modification of the Plug&Care Connector Establish plugin concept Get plugins with help of modularity of OSGi Handle plugins (registration) by the use of dependency injection provided by OSGi (Declarative Services)
Slide 37 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Designing Plug&Care Connector Plugin and Registry Concept using the Example of Driver
How did we realize it?
Slide 38 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Designing Plug&Care Connector Plugin and Registry Concept using the Example of Driver
Slide 39 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Designing Plug&Care Connector Plugin and Registry Concept using the Example of Driver
What does a driver developer need to do? Implement the driver interfaces provided by Plug&Care Connector Provide a component description like that:
<component name=„Driver A“> <implementation class="de.pncc.plugins.drivers.DriverA"/> <service> <provide interface="de.pncc.drivers.Driver"/> </service> </component>
Slide 40 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Designing Plug&Care Connector Plugin and Registry Concept using the Example of Driver
What does the Plug&Care Connecor do? Provides component description like that:
<component name=„Driver Registry„ <reference name="de.pncc.driver„ interface="de.pncc.drivers.Driver„ bind="addDriver„ unbind="removeDriver </component>
Implements bind and unbind method to e.g., store the driver in a list
Slide 41 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Designing Plug&Care Connector Plugin and Registry Concept using the Example of Driver
What does OSGi do? Everything else
like listen to new driver bundles, retrieving there provided driver services, inject them to the right place, handles uninstalled driver bundles, …
What did we learn?
ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
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Slide 45 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
What did We Learn?
Living out OSGi principles is a good base for building better software (in terms of maintance and deployment).
Slide 46 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Living out OSGi Principles Services Use services
Seperate service interface and service implementation Allows abstraction and loose coupling Makes application
More robust against changes Deployable in different environments just by assempling different kind of jar files
Slide 47 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Living out OSGi Principles Declarative Services Prerequisite is usage of services
Make use of dependency injection Let other maintain the code for dependency handling Get your code free from OSGi API Makes application
Easier to test by injecting stub or mock objects More robust because fewer lines of code (every reduced line of code, reduces the chance for a bug) Easier to understand and use by third party developers knowing nothing about OSGi
Slide 48 ApacheCon 2011 > Doreen Seider> Using OSGi to Build Better Software > 11.11.2011
Living out OSGi Principles Encapsulation Make only those code public which is really intended to be public
Hide as much as possible from the outer world In perfect word only the (service) interfaces are public Makes application
More robust against changes because third party code can only be depend on a little part of your applications‘s implementation Architecture smarter, because you need to think about it in more detail