OSGi fundamentals

Slides from my Liferay Symposium France 2016 talk aiming to explain the fundamental concepts behind OSGi (structured around Modularity Maturity Model) and what makes it the only true modular technology in Java world.

Transcript

1. @MilenDyankov OSGi Fundamentals
2. OSGi = Modularity
3. " When I use a word," Humpty Dumpty said, in rather a scornful tone, " it means just what I choose it to mean - neither more nor less."
4. Modularity Maturity Model proposed by Dr Graham Charters at the OSGi Community Event 2011 Level 1 Ad Hoc nothing Level 2 Modules decoupled from artifact Level 3 Modularity decoupled from identity Level 4 Loose-Coupling decoupled from implementation Level 5 Devolution decoupled from ownership Level 6 Dynamism decoupled from time
5. Level 1 Ad Hoc nothing Level 2 Modules decoupled from artifact Level 3 Modularity decoupled from identity Level 4 Loose-Coupling decoupled from implementation Level 5 Devolution decoupled from ownership Level 6 Dynamism decoupled from time Level 7 Peter Kriens only available to people who are Peter Kriens Modularity Maturity Model proposed by Dr Graham Charters at the OSGi Community Event 2011
6. Modularity Maturity Model proposed by Peter Kriens in foreword to “Java Application Architecture” Level 1 Ad Hoc Level 2 Modules Level 3 Modularity Level 4 Loose-Coupling Level 5 Devolution Level 6 Dynamism Unmanaged / chaos Managing dependencies Proper isolation Minimize coupling Service-oriented architecture
7. Level 1 Monolith Level 2 Composite Level 3 Containers Level 4 Discovery Level 5 JuServices Buzzword compliant Modularity Maturity Model
8. Level 1 Monolith Unaware of own dependencies Level 2 Composite Aware of infrastructural dependencies Level 3 Containers Aware of functional dependencies Level 4 Discovery Aware of functional requirements Level 5 Adapts to changing requirements JuServices Buzzword compliant Modularity Maturity Model
9. Level 1 Monolith Level 2 Composite Level 3 Containers Level 4 Discovery Level 5 JuServices Buzzword compliant Modularity Maturity Model
10. Level 1 Monolith Level 2 Composite Level 3 Containers Level 4 Discovery Level 5 JuServices Buzzword compliant Modularity Maturity Model
11. Buzzword compliant Modularity Maturity Model JuServices Level 1 Monolith Level 2 Composite Level 3 Containers Level 4 Discovery Level 5
12. Buzzword compliant Modularity Maturity Model JuServices Level 1 Monolith Level 2 Composite Level 3 Containers Level 4 Discovery Level 5 OSGi
13. product intermediate intermediate material
17. Product Entity Entity Entity Entity Entity Entity Offer Offer Offer Offer Offer Offer Offer Offer Offer Offer Offer
18. Application Artifact Artifact Artifact Artifact Artifact Artifact Export Export Export Export Export Export Export Export Export Export Export
19. Artifact Level 2 decoupled from artifact
20. Foo Level 2 decoupled from artifact Manifest-Version: 1.0 Bundle-ManifestVersion: 2 Bundle-Name: Foo Bundle-SymbolicName: com.foo Bundle-Vendor: Foo, Inc. Bundle-Version: 1.0.0 . . .
21. Buzzword compliant Modularity Maturity Model JuServices OSGi Level 1 Monolith Level 2 Composite Level 3 Containers Level 4 Discovery Level 5 OK!
22. Level 3 decoupled from identity Artifact Export Artifact
23. Level 3 decoupled from identity Require-Bundle: com.foo Foo Me
24. Level 3 decoupled from identity Export-Package ::= export ( ',' export)* List of packages (Java package + version) within this jar file that external code is allowed to access! Foo Me
25. Level 3 decoupled from identity Export-Package:\ com.standard.power.plugs;\ version=”1.0.0”,\ com.foo.power.plugs.shop;\ version=”2.3.0”;\ uses:=”com.standard.power.plugs”,\ ... Export-Package ::= export ( ',' export)* List of packages (Java package + version) within this jar file that external code is allowed to access! Foo Me
26. Level 3 decoupled from identity Import-Package ::= import ( ',' import )* List of packages (Java package + version-range) that classes in this jar file expect other bundles to provide! Foo Me
27. Level 3 decoupled from identity Import-Package:\ com.standard.power.plugs;\ version=”[1,2)”,\ com.foo.power.plugs.shop;\ version=”2.3.0”,\ com.other.power.plugs.shop;\ version=”1.5.0”,\ ... Foo Me Import-Package ::= import ( ',' import )* List of packages (Java package + version-range) that classes in this jar file expect other bundles to provide!
28. Buzzword compliant Modularity Maturity Model JuServices OSGi Level 1 Monolith Level 2 Composite Level 3 Containers Level 4 Discovery Level 5 OK! OK!
29. Level 4 decoupled from implementation Artifact Artifact Requirement Need to connect device to power outlet! Capability Can connect device to power outlet! RESOLVER
30. Level 4 decoupled from implementation Artifact Artifact Requirement Need to connect device to power outlet! Capability Can connect device to power outlet! RESOLVER Require-Capability: power.supply;\ filter:=”(& (voltage>110)\ (voltage<230))”,\ electrician;\ filter:=”(& (price<50)\ (certified=yes))”
31. Level 4 decoupled from implementation Artifact Artifact Requirement Need to connect device to power outlet! Capability Can connect device to power outlet! RESOLVER Require-Capability: power.supply;\ filter:=”(& (voltage>110)\ (voltage<230))”,\ electrician;\ filter:=”(& (price<50)\ (certified=yes))” org.osgi.framework.system.capabilities.extra= power.supply;voltage:Long=220
32. Level 4 decoupled from implementation Artifact Artifact Requirement Need to connect device to power outlet! Capability Can connect device to power outlet! RESOLVER Require-Capability: power.supply;\ filter:=”(& (voltage>110)\ (voltage<230))”,\ electrician;\ filter:=”(& (price<50)\ (certified=yes))” org.osgi.framework.system.capabilities.extra= power.supply;voltage:Long=220 Provide-Capability: electrician;price:Long=10;certified=yes
33. Buzzword compliant Modularity Maturity Model JuServices OSGi Level 1 Monolith Level 2 Composite Level 3 Containers Level 4 Discovery Level 5 OK! OK! OK!
34. Level 5 decoupled from ownership & time JuServices Artifact Artifact REGISTRY Service Service Service Service
35. Level 5 decoupled from ownership & time JuServices Artifact Artifact REGISTRY Service Service Service Service manifest manifest OSGi service registry REGISTER REGISTER manifest Interface Service 1 . . . Service N
36. Level 5 decoupled from ownership & time JuServices Artifact Artifact REGISTRY Service Service Service Service manifest manifest OSGi service registry REGISTER USE manifest Interface Service 1 . . . Service N REGISTER
37. Level 5 decoupled from ownership & time JuServices Artifact Artifact REGISTRY Service Service Service Service OSGi service registry SERVLET SERVLET GET GET REGISTER REGISTER HTTPServiceImpl HTTP Service HTTPServiceImpl REGISTER manifest
38. Level 5 decoupled from ownership & time JuServices Artifact Artifact REGISTRY Service Service Service Service manifest OSGi service registry HTTP Servlet REGISTER SERVLET SERVLET GET (when needed) HTTPServiceImpl Servlet1 (path=”/1”) Servlet2 (path=”/2”) REGISTER
39. Level 5 decoupled from ownership & time JuServices Artifact Artifact REGISTRY Service Service Service Service Register OSGI service (manually) SINGLETON PROPERTIES CONTRACT
40. Level 5 decoupled from ownership & time JuServices Artifact Artifact REGISTRY Service Service Service Service Use an OSGI service (manually) DONE WITH THE SERVICE START USING THE SERVCE FIND A SERVCE
41. Level 5 decoupled from ownership & time JuServices Artifact Artifact REGISTRY Service Service Service Service Declarative services and Service Component Runtime (SCR)
42. Level 5 decoupled from ownership & time JuServices Artifact Artifact REGISTRY Service Service Service Service /OSGI-INF/MyComponent.xml file: <?xml version="1.0" encoding="UTF-8"?> <scr:component name=”MyComponent” xmlns:scr=”http://www.osgi.org/xmlns/scr/v1.2.0”> <implementation class=”com.liferay.MyComponent”/> </scr:component> Manifest header: Service-Component: OSGI-INF/MyComponent.xml
43. Level 5 decoupled from ownership & time JuServices Artifact Artifact REGISTRY Service Service Service Service @Component( configurationPid=”hello.component.pid”, configurationPolicy=ConfigurationPolicy.OPTIONAL, enabled=true, immediate=true, name=”HelloComponent”, property={ ”vendor.name=Liferay”, ”other.property=value” }, service={HelloService.class, OtherService.class} ) public class HelloComponent implements MultiService { . . .
44. Level 5 decoupled from ownership & time JuServices Artifact Artifact REGISTRY Service Service Service Service @Activate void open(Map<String,?> properties) { } @Deactivate void close() { } @Modified void modified(Map<String,?> properties) { }
45. Level 5 decoupled from ownership & time JuServices Artifact Artifact REGISTRY Service Service Service Service @Reference( cardinality=ReferenceCardinality.MANDATORY, name = “LogService”, policy = ReferencePolicy.STATIC, policyOption=ReferencePolicyOption.RELUCTANT, service = LogService.class, target = “(vendor.name=Liferay)”, unbind = “unsetLog”, updated = “updatedLog” ) void setLog( LogService log) { } void unsetLog( LogService log) { } void updatedLog( Map<String,?> ref ) { }
46. Buzzword compliant Modularity Maturity Model JuServices OSGi Level 1 Monolith Level 2 Composite Level 3 Containers Level 4 Discovery Level 5 OK! OK! OK! OK!
47. The essence of modularity is Not knowing
48. The essence of modularity is Not knowing Which enforces optimization for Predictability
49. Which results in application Agility The essence of modularity is Not knowing Which enforces optimization for Predictability
50. milen.dyankov@liferay.com @MilenDyankov http://www.liferay.com @Liferay