OSGi & Spring combined

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2 C O N T E N T S What is OSGi Where does OSGi come from What is Spring Why this combination Problems An Example Conclusion -2-

3 Woher kommt OSGi OSGi-Alliance: org/ Developed since 1999 Originally for Embedded-Systems Now: Also used for enterprise and server-side side systems Applications based on a OSGi-Framework: Eclipse, IBM-Websphere Application-Server, Lotus, Adobe BEA Oracle -3-

4 C O N T E N T S What is OSGi Where does OSGi come from What is Spring Why this combination Problems An Example Conclusion -4-

5 What is OSGi - I A dynamic, service oriented module system for Java Source: OSGi.org A module system for Java which defines Modules (aka Bundles ), Visibility of Packages (public-api vs. private-api) Dependencies between Bundles Version of a Bundle. -5-

6 What is OSGi - II A dynamic, service oriented module system for Java Source: OSGi.org Bundles can be dynamically installed, started, stopped uninstalled and refreshed during runtime. -6-

7 What is OSGi - III A dynamic, service oriented module system for Java Source: OSGi.org Bundles can dynamically publish services Bundles can search for services in a global service repository and use them The runtime provides support for (de-)registration of services while the system is up and running -7-

8 C O N T E N T S What is OSGi Where does OSGi come from What is Spring Why this combination Problems An Example Conclusion -8-

9 Was ist Spring de-facto standard for Java EE Applications Simple programming model (POJOs) Inversion of Control / Dependency Injection AOP using different implementations Many technology abstractions and helpers Simple and technology independent d development of enterprise applications -9-

10 C O N T E N T S What is OSGi Where does OSGi come from What is Spring Why this combination Problems An Example Conclusion -10-

11 Why this combination - I OSGi == Embedded? - Spring == Enterprise?? Goal: Using the benefits of the OSGi Service Platform without loosing the benefits of Spring Splitting up your application in Bundles to use Dependency Management Visibility Management Versions-Management Dynamic behavior Deploying Spring as Bundles -11-

12 Why this combination - II Boundary conditions Complexity It must still be as easy to use as Spring is POJO programming model Integration with the OSGi-Service-Model OSGi-Services as Beans and vice versa Testing Must be possible without an OSGi-Container If possible, no dependencies to the OSGi-APIs The enterprise features of Spring must still be available -12-

13 C O N T E N T S What is OSGi Where does OSGi come from What is Spring Why this combination Problems An Example Conclusion -13-

14 Problems in general Class loading Many 3rd-party libraries expect to see and work on a linear Java Class path No linear Class path in OSGi Using strategies to load Classes Buddy Class loading ContextClassLoader Dynamic behavior What to do if a part of my application is not available?? How to handle the different versions? Which 3rd-party libraries can I use? -14-

15 Problems in particular It is still pretty new stuff Broken builds Bugs Missing features Examples: Persistence layer: Class loading problems Problems with OSGi s dynamic behavior Web Not yet implemented Also some open questions -15-

16 C O N T E N T S What is OSGi Where does OSGi come from What is Spring Why this combination Problems An Example Conclusion -16-

17 Example I OSGi Spring Application(s) -17-

Spring-OSGi creates and destroys the Context automatically whenever a

18 Example II Bundles and Spring Normal Spring-Apps: 1 ApplicationContext Spring-OSGi: One App == several Bundles One ApplicationContext per Bundle: Spring-OSGi creates and destroys the Context automatically whenever a bundle was (de-)activated Defining the ApplicationContext in META-INF/spring -18-

19 Example III Beans as OSGi Service Spring-Beans can be exported as an OSGi-ServiceService OSGi-Services are visible for all bundles <beans> <bean name="customerservice" class="de.example.customerservice.internal.customerserviceimpl" /> <osgi:service i id="customerserviceosgi" i i" ref="customerservice" interface="de.example.customerservice.customerservice" /> </beans> -19-

Example IV OSGi Service as Beans Using existing OSGi-Services

id="customerserviceosgi" i i" interface="de.example.

customerservice"/> <bean id="orderservice" class="de.example.

20 Example IV OSGi Service as Beans Using existing OSGi-Services within your Spring-Context <beans> <osgi:reference id="customerserviceosgi" i i" interface="de.example.customerservice.customerservice"/> <bean id="orderservice" class="de.example.orderservice.internal.orderserviceimpl"> <property name="customerservice"> <ref local="customerserviceosgi"/> </property> </bean> </beans> -20-

21 Example V jpetstore jpetstore is a Spring example 3 Layers ibatis RMI, HTTP, Hessian and Burlap for remoting JSPs and Spring- WebMVC -21-

22 Example VI jpetstore Architecture I Bundles and their dependencies Export:...dataaccess Internal:...internal.dataaccess...internal.dataaccess.ibatis...internal.dataaccess.ibatis.maps dataaccess import...dataaccess Export:...domain Export:...domain.logic...domain.logic.validator Internal:...domain.internal.logic domain.logic import...domain domain import...domain.logic...domain.logic.validator Export: Internal:...internal.web...internal.web.spring web -22-

23 Example VII jpetstore Architecture II Domain model and Database mapping Account mapped to Account 1 -account mapped to Order mapped to LineItem Order 1..* -items LineItem -quantity : int 1 -item mapped to Product CartItem -item 1 Item 0..* -cartitems -items 0..* Cart -product 1 Product -category 1 Category mapped to Item mapped to Category -23-

24 Example VIII jpetstore Architecture III Services dataaccess DataSource <<uses>> PropertyPlaceholder <<uses>> AccountDao CategoryDao ProductDao ItemDao OrderDao TransactionManager domain.logic <<uses>> <<AOP>> <<uses>> TransactionAdvice OrderValidator AccountValidator PetStore <<uses>> exporter web servlets <<uses>> httppetstore client client rmipetstore rmipetstore...controller -24-

25 C O N T E N T S What is OSGi Where does OSGi come from What is Spring Why this combination Problems An Example Conclusion -25-

26 Conclusion No OSGi-API used Visibility could be defined not only on package-level but also for Spring beans Dependency Injection Many other possibilities Service cardinalities Service-Listener Property-Placeholder -26-

27 Thank you for your attention Questions? -27-

Spring and OSGi. Martin Lippert akquinet agile GmbH Bernd Kolb Gerd Wütherich

Spring and OSGi. Martin Lippert akquinet agile GmbH Bernd Kolb Gerd Wütherich Spring and OSGi Martin Lippert akquinet agile GmbH lippert@acm.org Bernd Kolb b.kolb@kolbware.de Gerd Wütherich gerd@gerd-wuetherich.de 2006 by Martin Lippert, Bernd Kolb & Gerd Wütherich, made available