CS5233 Components Models and Engineering

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1 Prof. Dr. Th. Letschert CS5233 Components Models and Engineering (Komponententechnologien) Master of Science (Informatik) OSGI Bundles and Services

2 Slides on OSGi are based on OSGi Alliance: OSGi Service Platform Core Specification OSGi 2009 J. McAffer, P. Vanderlei, S. Archer: OSGi and Equinox, Addison-Wesley 2010 Bundles Wütherich/Hartmann/Kolb/Lübken, Die OSGI Service Platform Dpunkt Verlag, 2008 Seite 2

3 Eclipse / RCP Hello World Bundle Context download and install Eclipse for RCP Developers or install General Purpose Tools / Eclipse Plugin Development Environment RCP, Plugin, Bundle: RCP = Rich Client Platform Eclipse RCP Framework / platform / run-time for RCP applications makes it easy to create rich client applications RCP-Application = Application logic as plugin / bundle + Eclipse-RCP run-time Seite 3

4 Eclipse / RCP Hello World Bundle Example: Hello World Bundle Create a new Plug-in Project called HelloWorld Wizard page 1: target platform: choose OSGi / standard target platform is about who will run the plugin OSGi means that it will run directly on an OSGi framework (not within eclipse) standard means do not use special Equinox-extension Wizard page 2: Execution environment is an OSGi concept, it denotes the minimum Java runtime for the bundle, do not select anything choose generate Activator! Activator is the activator for the bundle as specified by OSGi A bundle is activated by calling its Bundle Activator object, if one exists. The BundleActivator interface defines methods that the Framework invokes when it starts and stops the bundle. OSGi Core Specification, The Activator must be declared in the manifest file with the header Bundle-Activator: <full qualified class name> Wizard page 3: do not select a template Seite 4

5 Eclipse / RCP Hello World Bundle Created files: MAINIFEST.MF Activator.java build.properties manifest file activator class template packaging / deployment configuration file Seite 5

6 Eclipse / RCP Hello World Bundle Created files: MAINIFEST.MF manifest file Manifest-Version : 1.0 Bundle-ManifestVersion : 2 Bundle-Name: HelloWorld Bundle-SymbolicName: HelloWorld Bundle-Version: qualifier Bundle-Activator : helloworld.activator Import-Package: org.osgi.framework;version="1.3.0" We are creating an OSGi-Bundle, this is its Manifest. Seite 6 MANIFEST.MF

7 Eclipse / RCP Hello World Bundle Created files: Activator.java activator class template package helloworld; import org.osgi.framework.bundleactivator; import org.osgi.framework.bundlecontext; public class Activator implements BundleActivator { private static BundleContext context; static BundleContext getcontext() { return context; /* * (non-javadoc) org.osgi.framework.bundleactivator#start(org.osgi.framework.bundlecontext) */ public void start(bundlecontext bundlecontext) throws Exception { Activator.context = bundlecontext; Activator.java /* * (non-javadoc) org.osgi.framework.bundleactivator#stop(org.osgi.framework.bundlecontext) */ public void stop(bundlecontext bundlecontext) throws Exception { Activator.context = null; OSGi Core Spec. Seite 7

$. = src/ output.. = bin/ bin.includes = META-INF/,\. build.$

8 Eclipse / RCP Hello World Bundle Created files: build.properties packaging / deployment configuration file build.properies source.. = src/ output.. = bin/ bin.includes = META-INF/,\. build.properties, as seen by the build properties editor Seite 8 and seen by a text editor

9 Eclipse / RCP Hello World Bundle fill the Activator with some code package helloworld; import org.osgi.framework.bundleactivator; import org.osgi.framework.bundlecontext; public class Activator implements BundleActivator { private static BundleContext context; static BundleContext getcontext() { return context; /* * (non-javadoc) org.osgi.framework.bundleactivator#start(org.osgi.framework.bundlecontext) */ public void start(bundlecontext bundlecontext) throws Exception { Activator.context = bundlecontext; System.out.println("Hello Bundle"); /* * (non-javadoc) org.osgi.framework.bundleactivator#stop(org.osgi.framework.bundlecontext) */ public void stop(bundlecontext bundlecontext) throws Exception { Activator.context = null; System.out.println("Goodby world - the bundle stops."); Seite 9 Activator.java

10 Eclipse / RCP Hello World Bundle run it in an OSGi framework Run Run as OSGi Framework osgi> Hello Bundle. should appear in the console (after several exception messages) create a minimal run configuration run it: Run Run as OSGi Framework open the run configuration: Run Run Configurations / OSGi Framework edit the configuration rename it to HelloWorldConfig deselected everything besides HelloWorld org.eclipse.osgi export bundle Export Deployable Plugins and Fragments wizard next Page: select and name a directory / finish Seite 10

Eclipse / RCP Hello World Bundle start OSGi console; install start stop the plugin > java -jar /path/to/eclipse/plugins/org.eclipse.osgi_3.6.2.r36x_v20110210.

11 Eclipse / RCP Hello World Bundle start OSGi console; install start stop the plugin > java -jar /path/to/eclipse/plugins/org.eclipse.osgi_3.6.2.r36x_v jar -console osgi> install file:/path/to/my/plugins/helloworld_ jar Bundle id is 1 osgi> start 1 Hello Bundle osgi> ss Framework is launched. id State Bundle 0 ACTIVE org.eclipse.osgi_3.6.2.r36x_v ACTIVE HelloWorld_ osgi> stop 1 Goodby world - the bundle stops. osgi> generated bundle (jar file) with manifest Seite 11

12 Eclipse / RCP Hello World Bundle Summary: Bundles are developed as Plugin projects in Eclipse Eclipse uses a directory structure for bundles that differs from the structure of the jar file By exporting the project Eclipse creates a bundle-jar The most simplistic bundle consists of a manifest file a class that implements org.osgi.framework.bundleactivator The activator has a start method that gets called when the bundle is started a stop method that gets called when the bundle is stopped For details of eclipse see: Seite 12

13 Bundle, Bundle Activator and Context org.osgi.framework Interface BundleActivator Activator: Activator: manifest entry Bundle-Activator: <fully qualified class name> class that implements interface BundleActitivator If an activator class exists (and is named in the manifest file) the bundle class loader will load the class and the framework will create an object of this type (using newinstance so it has to have a default constructor) its start / stop methods will be called by the framework Methods of interface BundleActitivator start(bundlecontext) Method to allocate resources, start threads, register services Bundles must be stopped by the framework if this method throws an exception stop(bundlecontext) Method called if the bundle is stopped (except if it stopped via an exception thrown by start). Should be used to deallocate resources allocated by start, services do not have to be unregistered. OSGi Service Platform Release 4 Version 4.1 Seite 13

14 Bundle, Bundle Activator and Context Activation Policy: Activation policy: How should a bundle be activated: eager or lazy Manifest entry Bundle-ActivationPolicy: lazy [ ; in/exclude directives] Eager activation (default) bundle is activated when started Lazy activation bundle is not to be activated immediately when started, instead activation is to be deferred until at least one of its classes is loaded Include / exclude directives (optional with lazy activation) include: packages with classes that should trigger activation exclude: packages with classes that should not trigger activation OSGi Core Spec. Seite 14

15 Bundle, Bundle Activator and Context org.osgi.framework Interface BundleContext Bundle Context: Bundle Context : Object of type BundleContext Proxy to the framework for a bundle Created when a bundle is started Passed as argument to the start method Can be used to: Obtain information about the framework Install new bundles Interrogate other bundles Obtain a persistent storage. Retrieve service objects of registered services. Register services. Subscribe or unsubscribe to events. OSGi Core Spec. Seite 15

16 Bundle, Bundle Activator and Context osgi> ss Framework is launched. Example : get information about id State Bundle 0 ACTIVE org.eclipse.osgi_3.6.2.r36x_v bundles and framework 2 INSTALLED HelloWorld_ osgi> start 2 All bundles: Bundle: org.eclipse.osgi_3.6.2.r36x_v [0] state: 32 ACTIVE package helloworld; Bundle: HelloWorld_ [2] state: 8 STARTING Framework Properties: Version: import org.osgi.framework.bundle; Vendor: Eclipse import org.osgi.framework.bundleactivator; OS: Linux import org.osgi.framework.bundlecontext; Processor: x86-64 import org.osgi.framework.constants; public class Activator implements BundleActivator {... public void start(bundlecontext bundlecontext) throws Exception { Activator.context = bundlecontext; System.out.println("All bundles:"); for (Bundle bundle: bundlecontext.getbundles()) { System.out.print("Bundle: " + bundle + " state: " + bundle.getstate()); if (bundle.getstate() == 1) System.out.print(" UNINSTALLED "); if (bundle.getstate() == 2) System.out.print(" INSTALLED "); if (bundle.getstate() == 4) System.out.print(" RESOLVED "); if (bundle.getstate() == 8) System.out.print(" STARTING "); if (bundle.getstate() == 16) System.out.print(" STOPPING "); if (bundle.getstate() == 32) System.out.print(" ACTIVE "); System.out.println(); System.out.println("Framework Properties: "); System.out.println("Version: " + context.getproperty(constants.framework_version) ); System.out.println("Vendor: " + context.getproperty(constants.framework_vendor) ); System.out.println("OS: " + context.getproperty(constants.framework_os_name) ); System.out.println("Processor: " + context.getproperty(constants.framework_processor) );... Seite 16

17 Bundle: Activator and Context org.osgi.framework Interface Bundle Bundle Objects of type Bundle represent installed bundles Bundle objects may be used to: get information about the bundle including the bundle's meta information manage the lifecycle of an installed bundle access a bundle's context Seite 17

18 Bundle, Bundle Activator and Context Example : List all headers of bundle with id 0 public void start(bundlecontext bundlecontext) throws Exception { Activator.context = bundlecontext; Bundle bundle_0 = context.getbundle(0); System.out.println(bundle_0 + " with Enumeration<String> keys = bundle_0.getheaders().keys(); while (keys.hasmoreelements()) { String key = keys.nextelement(); System.out.println(key + " \t" + bundle_0.getheaders().get(key)); org.eclipse.osgi_3.6.2.r36x_v [0] with headers: Manifest-Version 1.0 Bundle-DocUrl Main-Class org.eclipse.core.runtime.adaptor.eclipsestarter Bundle-Localization systembundle Bundle-RequiredExecutionEnvironment J2SE-1.5,OSGi/Minimum-1.2 Bundle-SymbolicName org.eclipse.osgi; singleton:=true...etc... the Mainfest headers Manifest-Version: 1.0 Bundle-DocUrl: Main-Class: org.eclipse.core.runtime.adaptor.eclipsestarter Bundle-Localization: systembundle Bundle-RequiredExecutionEnvironment: J2SE-1.5,OSGi/Minimum-1.2 Bundle-SymbolicName: org.eclipse.osgi; singleton:=true... org.eclipse.osgi_3.6.2.r36x_v jar/meta-inf/manifest Seite 18

19 Bundle, Bundle Activator and Context Example : install and start HelloWorld bundle public void start(bundlecontext context) throws Exception { System.out.println("The bundle loading bundle is starting"); Bundle bundle = context.installbundle("file:/path/to/helloworld.jar"); bundle.start(); System.out.println(bundle + " with headers:"); Enumeration<String> keys = bundle.getheaders().keys(); while (keys.hasmoreelements()) { String key = keys.nextelement(); System.out.println(key + " \t" + bundle.getheaders().get(key)); bundle.stop(); Seite 19

20 Events and Listener org.osgi.framework Class BundleEvent org.osgi.framework Class FrameworkEvent Events Objects of type BundleEvent are generated by the framework report on changes in the life-cycle of a bundle are delivered to BundleListeners registered with the framework have a type that represents the bundle's state change INSTALLED, RESOVED, STARTED, Objects of type FrameworkEvent are generated by the framework report on changes in the life-cycle of the framework are delivered to FrameworkListeners registered with the framework have a type that represents events within the framework STARTED, ERROR, WARNING, Seite 20

21 Events and Listeners org.osgi.framework Interface BundleListener org.osgi.framework Interface FrameworkListener Listener Objects of type BundleListner are registered with the framework (representet by a bundle context object) are called with an event of type BundleEvent when a bundle's lifecycle state has changed Objects of type FrameworkEvent are registered with the framework (representet by a bundle context object) are called with an event of type FrameworkEvent when the framework starts, stops, is refreshed, or when an error occurs Seite 21

22 Events and Listeners Example : monitor bundle events public void start(bundlecontext bundlecontext) throws Exception { bundlecontext.addbundlelistener(new BundleListener() public void bundlechanged(bundleevent event) { System.out.println("EVENT : a Bundle event occured "); System.out.println("\t type: " + decode(event.gettype()) + "\n\t for bundle:" + event.getbundle().getsymbolicname()); ); Bundle bundle = bundlecontext.installbundle( "file:/home/thomas/tmp/rcp/plugins/helloworld_ jar"); bundle.start(); bundle.update(); bundle.stop(); EVENT : a Bundle event occured bundle.uninstall(); Goodby world - the bundle stops. type: STARTED for bundle:helloworld public void stop(bundlecontext bundlecontext) throws Exception { EVENT : a Bundle event occured Activator.context = null; type: STOPPED System.out.println("Goodby world - the bundle stops."); for bundle:helloworld EVENT : a Bundle event occured type: UNRESOLVED for bundle:helloworld private static String decode(int type) { EVENT : a Bundle event occured switch (type) { type: UNINSTALLED case 1: return "INSTALLED"; case 2: return "STARTED"; for bundle:helloworld case 4: return "STOPPED"; case 8: return "UPDATED"; EVENT : a Bundle event occured case 16: return "UNINSTALLED"; case 32: return "RESOLVED"; type: STARTED case 64: return "UNRESOLVED"; case 128: return "STARTING"; for bundle:helloworld case 256: return "STOPPING"; case 512: return "LAZY_ACTIVATION"; EVENT : a Bundle event occured default: return "??" + type + "??"; type: STARTED for bundle:org.eclipse.osgi org.osgi.framework.frameworkevent Seite 22

23 Bundle Relations: Require / Import / Export Seite 23

24 Bundle: Import / Export Inter-bundle relationships direct : Bundle A has access to bundle B via import / export indirect : Bundle A uses a service provided by bundle B, this relationship is always mediated by the framework Direct usage Require Bundle Import every package that is export by the bundle Syntax: Require-Bundle ::= bundle-description ( ',' bundle-description )* bundle-description ::= symbolic-name (';' parameter )* Import Package Import named package of a bundle should be preferred in general Syntax: Import-Package ::= import ( ',' import )* import ::= package-names ( ';' parameter )* package-names ::= package-name ( ';' package-name )* Seite 24

25 Bundle: Import Export / Require Bundle Import via Require Bundle Example: Greeting Bundle Exporter Create Plugin-Project GreetingBundle without Activator Create class greetingbundle.hello with public method sayhello sayhello should print Hello World add Export-Package: greetingbundle to the manifest Importer Create Plugin-Project GreetingUserBundle with Activator add Require-Bundle: GreetingBundle;bundle-version=" " to the manifest Seite 25

Bundle: Import Export / Require Bundle Greeting Bundle create, add Class Hello change version and provider package greetingbundle; public class Hello { public void sayhello() { System.out.

26 Bundle: Import Export / Require Bundle Greeting Bundle create, add Class Hello change version and provider package greetingbundle; public class Hello { public void sayhello() { System.out.println("Hello! says the greeting bundle"); generated manifest Manifest-Version: 1.0 Bundle-ManifestVersion: 2 Bundle-Name: de.thm.mni.greetingbundle Bundle-SymbolicName: GreetingBundle Bundle-Version: Bundle-RequiredExecutionEnvironment: JavaSE-1.6 Bundle-Vendor: de.thm.mni Seite 26

Bundle: Import Export / Require Bundle Greeting Bundle add package export modified manifest Manifest-Version: 1.0 Bundle-ManifestVersion: 2 Bundle-Name: de.thm.mni.

27 Bundle: Import Export / Require Bundle Greeting Bundle add package export modified manifest Manifest-Version: 1.0 Bundle-ManifestVersion: 2 Bundle-Name: de.thm.mni.greetingbundle Bundle-SymbolicName: GreetingBundle Bundle-Version: Bundle-RequiredExecutionEnvironment: JavaSE-1.6 Bundle-Vendor: de.thm.mni Export-Package: greetingbundle Seite 27

greetinguserbundle Bundle-SymbolicName: GreetingUserBundle Bundle-Version: 1.0.0.0 Bundle-Activator: greetinguserbundle.

28 Bundle: Import Export / Require Bundle Greeting User Bundle create using bundle, add require bundle modified manifest Manifest-Version: 1.0 Bundle-ManifestVersion: 2 Bundle-Name: de.thm.mni.greetinguserbundle Bundle-SymbolicName: GreetingUserBundle Bundle-Version: Bundle-Activator: greetinguserbundle.activator Import-Package: org.osgi.framework;version="1.3.0" Bundle-RequiredExecutionEnvironment: JavaSE-1.6 Bundle-Vendor: de.thm.mni Require-Bundle: GreetingBundle;bundle-version="1.0.0" Seite 28

29 Bundle: Import Export / Require Bundle Greeting User Bundle create using/importing class... Eclipse manages import of required bundles! Seite 29

30 Bundle: Import Export / Require Bundle Greeting User Bundle... add using statement to activator Seite 30

31 Bundle: Import - Export / Require Bundle Export bundles ( plugins ) create minimal configuration then export as deployable plug-ins and fragments Seite 31

32 Bundle: Import - Export / Require Bundle Export bundles ( plugins ) create minimal configuration (org.eclipse.osgi, GreetingUserBundle) then export as deployable plug-ins and fragments Seite 32

33 Bundle: Import - Export / Require Bundle Test bundles osgi> ss Framework is launched. id 0 State Bundle ACTIVE org.eclipse.osgi_3.6.2.r36x_v osgi> install file:/home/thomas/tmp/rcp/plugins/greetingbundle_ jar Bundle id is 4 osgi> install file:/home/thomas/tmp/rcp/plugins/greetinguserbundle_ jar Bundle id is 5 osgi> ss Framework is launched. id State Bundle ACTIVE org.eclipse.osgi_3.6.2.r36x_v INSTALLED GreetingBundle_ INSTALLED GreetingUserBundle_ osgi> start 4 osgi> start 5 Hello! says the greeting bundle osgi> Seite 33

34 Bundle: Import - Export / Import Package Import via Import Package modify the using bundle GreetingUserBundle: 1. remove require bundle statement Seite 34

Bundle: Import - Export / Import Package Import via Import Package modify the using bundle GreetingUserBundle: 2. Let Eclipse generate the import Seite 35 Manifest-Version: 1.

35 Bundle: Import - Export / Import Package Import via Import Package modify the using bundle GreetingUserBundle: 2. Let Eclipse generate the import Seite 35 Manifest-Version: 1.0 Bundle-ManifestVersion: 2 Bundle-Name: de.thm.mni.greetinguserbundle Bundle-SymbolicName: GreetingUserBundle Bundle-Version: Bundle-Activator: greetinguserbundle.activator Import-Package: greetingbundle, org.osgi.framework;version="1.3.0" Bundle-RequiredExecutionEnvironment: JavaSE-1.6 Bundle-Vendor: de.thm.mni

36 Bundle: Import - Export / Import Package Import via Import Package export the new version and test it osgi> ss Framework is launched. id State ACTIVE ACTIVE INSTALLED Bundle org.eclipse.osgi_3.6.2.r36x_v GreetingBundle_ GreetingUserBundle_ osgi> start 6 Hello! says the greeting bundle osgi> stop 6 osgi> uninstall 6 osgi> install file:/home/thomas/tmp/rcp/plugins/greetinguserbundle_ jar Bundle id is 7 osgi> ss Framework is launched. id State ACTIVE ACTIVE INSTALLED Bundle org.eclipse.osgi_3.6.2.r36x_v GreetingBundle_ GreetingUserBundle_ osgi> start 7 Hello! says the greeting bundle Seite 36

37 Bundle: Import - Export / Version Versions Bundle version Bundles have a version Default value : Specified with the Bundle-Version header Syntax: Bundle-Version ::= version version ::= major( '.' minor ( '.' micro ( '.' qualifier )? )? )? mayor ::= number minor ::= number micro ::= number qualifier ::= ( alphanum _ '-' )+ Components that are not specified, they have a default value of 0. If the qualifier component is not specified, it has a default value of the empty string. Bundles are identified by the combination of symbolic name and version Requiring bundle specifies a version constraint Require-Bundle: <bundlename>; bundle-version= <versionrange> Required bundle must match the version constraint Seite 37

38 Bundle: Import - Export / Version Versions Package version Packages may have a version (not related to bundle version) Specified as part of the package import / export header Import specifies a version constraint Import-Package: <packagename>; version= <versionrange> Export must match the version constraint Seite 38

39 Bundle: Import - Export / Version Versions Version Ranges Example: 1.1 means all versions v with <= v Example: (1.1, 2.1] means all versions v with < v <= [, ] range inclusive (, ) range exclusive Seite 39

40 Bundle: Import - Export / Dynamic Import Dynamic Import of Packages Header: DynamicImport-Package: <comma separated list of package names with wildcards> Example: DynamicImport-Package: * Packages are imported when needed Dynamic Imports The DynamicImport-Package header is intended to look for an exported package when that package is needed. The key use case for dynamic import is the Class forname method when a bundle does not know in advance the class name it may be requested to load. [OSGi-Spec] Seite 40

41 Bundle: Class Loading Class Loading Each bundle has its own class loader Bundle loader is created by the framework after the bundle has been resolved Class loading in a bundle is performed in these steps: java.* classes are loaded by the parent class loader of the bundle (usually the boot loader) bundles referencing classes of imported packages loading is delegated to the exporting bundle, starting with this step bundles referencing classes of required other bundles or that are importing from several other bundles delegate loading to required bundles in the the order they appear in the manifest the bundle class path is searched for the class search for classes in exported packages ends here if the class may be in a dynamically imported package an appropriate exporter is searched, if successful, the class form now on is treated as if in an explicitly imported package search for the class ends here Seite 41

42 Bundle: Class Loading OSGI-Spec. Seite 42

43 Services Seite 43

44 Services / Example Introductory Example: Hello World Service Create plugin project HelloService with activator Create plugin project HelloServiceUser with activator Seite 44

45 Services / Example Hello World Service / define the service package helloservice; public interface HelloService { void sayhello(); the service definition as interface package helloserviceimpl; import helloservice.helloservice; public class HelloServiceImpl implements HelloService public void sayhello() { System.out.println("Hello - this service is brought to you by the HelloService"); Seite 45 the service implementation

46 Services / Example Hello World Service / register the service in the activator public class Activator implements BundleActivator { private static BundleContext context;... public void start(bundlecontext bundlecontext) throws Exception { Activator.context = bundlecontext; System.out.println("hello service started"); Class<?> serviceinterface = HelloService.class; Object serviceimpl = new HelloServiceImpl(); Dictionary<String, String> properties = new Hashtable<String, String>(); context.registerservice(serviceinterface.getname(), serviceimpl, properties); System.out.println("helloservice: HelloService registered");... Seite 46

Services / Example Hello World Service / export package with service interface The generated manifest of the service bundle Manifest-Version: 1.0 Bundle-ManifestVersion: 2 Bundle-Name: de.thm.mni.

47 Services / Example Hello World Service / export package with service interface The generated manifest of the service bundle Manifest-Version: 1.0 Bundle-ManifestVersion: 2 Bundle-Name: de.thm.mni.helloservice Bundle-SymbolicName: HelloService Bundle-Version: Bundle-Activator: helloservice.activator Import-Package: org.osgi.framework;version="1.3.0" Bundle-RequiredExecutionEnvironment: JavaSE-1.6 Bundle-Vendor: de.thm.mni Export-Package: helloservice Seite 47

48 Services / Example Hello World Service User / use the service within the activator The activator of the service user Seite 48

49 Services / Example Hello World Service User / use the service within the activator package helloserviceuser; import org.osgi.framework.bundleactivator; import org.osgi.framework.bundlecontext; import org.osgi.framework.servicereference; import helloservice.helloservice; public class Activator implements BundleActivator { private static BundleContext context;... public void start(bundlecontext bundlecontext) throws Exception { Activator.context = bundlecontext; System.out.println("hello service user: started"); ServiceReference helloserviceref = context.getservicereference("helloservice.helloservice"); if (helloserviceref == null) { System.out.println("hello service user: cannot reference hello service"); else { try { System.out.println("hello service user: ServiceReference found " + helloserviceref); HelloService helloservice = (HelloService) context.getservice(helloserviceref); System.out.println("hello service user: hello service resolved " + helloservice); helloservice.sayhello(); catch (Exception e) { System.out.println(e);... The activator of the service user Seite 49

50 Services / Example Hello World Service / Test When testing with eclipse make sure that the service defining bundle is started before the service user by setting appropriate start levels! Seite 50

51 Services / Example Hello World Service / Test Seite 51

52 Services Services Service An object registered with the service registry under one or more interfaces together with properties. This object can be discovered and used by bundles. Service Registry Holds the service registrations. Service Reference A reference to a service. Provides access to the service s properties but not the actual service object. The service object must be acquired through a bundle s Bundle Context. Service consumer Service consumer Registry Registry Service Reference Service Service provider Service provider Seite 52

53 Services Service Service name Fully qualified name of the service interface. Service interface Defines the service semantically. - The class of the service object may also be used as interface. Service object Implementation of a service. Owned by and run within the defining bundle. Service properties Dictionary of key (a string) value pairs which describe the service. (Optional) Seite 53

54 Services Service registration Making a service available by publishing it. Service may be unregistered explicitly is unregistered implicitly when the registrating bundle is uninstalled Registration in done by calling methods of a BundleContext registerservice(string name, Object service, Dictionary properties) For a service object registered under a single service interface. registerservice(string[] names, Object service, Dictionary properies) For a service object registered under multiple service interfaces. Framework ensures that the registered object is an instance of the service interface and returns a service reference object. Seite 54

55 Services Service locating Get a reference to a service. To use a service the user first has to obtain a service reference by calling methods of a BundleContext getservicereference(string name) Returns a reference to a service object registered under the name. getservicereference(string name, String filter) Returns a reference to a service object registered under the name satisfying the filter. To get a service object the user calls a method of a BundleContext getservice(servicereference reference) Returns a service object. Seite 55

56 Services / Properties Service properties java.util.dictionary<string, ValueType> object, where ValueType should be a basic Java type defined in defined java.* Properties describe the service and may be used to get information about a service to query the registry for a service using a filter in oder to find a matching service All keys are not case sensitive are within common name-space when filtering and should be unique across services Keys of the form service.* are reserved, some of them are predefined Filtering Filter: An expression according to the syntax of LDAP-search filters may be used to match properties of a service reference Seite 56

57 Services / Filter org.osgi.framework Interface Filter Filtering Creation of filters is supported by objects of type BundleContext and by class FrameworkUtil: Filter createfilter(string filter)throws InvalidSyntaxException A filter supports matching: match(servicereference) Match the properties of the Service Reference performing key lookup in a case insensitive way. match(dictionary) Match the entries in the given Dictionary object performing key lookup in a case insensitive way. matchcase(dictionary) Match the entries in the given Dictionary object performing key lookup in a case sensitive way. Example: String filterstring = "(java.util.currency=chf)" ; Filter filter = FrameworkUtil. createfilter (filterstring); if (filter.match(myserviceref)) { MyService myservice = (MyService) context.getservice(myserviceref); Seite 57

58 Services / Service Factory org.osgi.framework Interface ServiceFactory Service Factories A Service Factory is a Service object that implements ServiceFactory If the service objects implements this interface it will will not be returned directly by context.getservice(servicereference) instead context.getservice delegates creation of the service object to its factory method: getservice(bundle serviceuser, ServiceRegistration registobj) This method is called by the Framework if a call is made to BundleContext.getService and the following are true: The ServiceReference argument to BundleContext.getService refers to a service object that implements the ServiceFactory interface. The bundle s usage count of that service object is zero; that is, the bundle currently does not have any dependencies on the service object. The call to BundleContext.getService must be routed by the framework to this method, passing to it the Bundle object of the caller. Seite 58

59 Services / Service Factory package helloservice; Factory Example import org.osgi.framework.bundle; import org.osgi.framework.servicefactory; import org.osgi.framework.serviceregistration; public class HelloServiceFactory implements ServiceFactory public Object getservice(bundle bundle, ServiceRegistration registration) { System.out.println("Hey bundle " + bundle + " needs my service"); return new public void ungetservice(bundle bundle, ServiceRegistration registration, Object service) { package helloservice; import import import import java.util.dictionary; java.util.hashtable; org.osgi.framework.bundleactivator; org.osgi.framework.bundlecontext; public class Activator implements BundleActivator { public void start(bundlecontext context) throws Exception { Class<?> serviceinterface = HelloService.class; Object serviceimpl = new HelloServiceFactory (); Dictionary<String, String> properties = new Hashtable<String, String>(); context.registerservice(serviceinterface.getname(), serviceimpl, properties); public void stop(bundlecontext context) throws Exception { Seite 59

OSGi in Action. Ada Diaconescu

OSGi in Action. Ada Diaconescu OSGi in Action Karl Pauls Clement Escoffier karl.pauls@akquinet.de clement.escoffier@akquinet.de INF 346. Ada Diaconescu ada.diaconescu@telecom-paristech.fr 2 OSGi in Action - Clement Escoffier (clement.escoffier@akquinet.de)