Using OSGi in Nakamura

Using OSGi in Nakamura

Carl [email protected] Technologies

15 June 2010

Overview

• Apache Felixo Dependency Injectiono Dynamic loading/unloadingo Instantiation by configuration

• BND plugin generates manifesto Export-Package, Private-Package, Include-Resource

• SCR plugin generates descriptorso Declarative Serviceso Configuration Admino Metatype services

11th Sakai Conference - June 15-17, 2010

Starting Lineup

• Bundles• Components• Dependency Injection• Configuration


Bundles


Bundle Life Cycle

• INSTALLEDo Successfully installed in container

• RESOLVEDo All resources available; ready to start or has stopped

• STARTINGo Activator.start called; waiting for return

• ACTIVEo No errors during start; activator has returned

• STOPPINGo Activator.stop called; waiting for return

• UNINSTALLEDo Cannot move to any other state


Bundle Activation

import org.osgi.framework.BundleActivator;import org.osgi.framework.BundleContext;

public class Activator implements BundleActivator {public void start(BundleContext context) {System.out.println("Starting: Hello World");}

public void stop(BundleContext context) {System.out.println("Stopping: Goodbye Cruel World");}}

Source: Wikipedia


Components


Types of Components

• Componento Singletono Consumes functionality

• Serviceo Singletono Consumes & offers functionality

• Service Factoryo Creates a service per bundleo Not configurable

• Component Factoryo Creates a service per callo Fully configurable


Service Example

@Component@Servicepublic class LdapAuthenticationPlugin implements AuthenticationPlugin { @Property(value = "o=sakai") static final String LDAP_BASE_DN = "sakai.auth.ldap.baseDn"; private String baseDn;

@Reference private LdapConnectionManager connMgr;

@Activate protected void activate(Map<?, ?> props) { baseDn = OsgiUtil.toString(props.get(LDAP_BASE_DN), "o=sakai"); }}


Component Execution

@Activateprotected void activate(ComponentContext ctx) {}protected void activate(BundleContext ctx) {}protected void activate(Map<?, ?> props) {}

@Modifiedprotected void modified(...) {}

@Deactivateprotected void deactivate(...) {}protected void deactivate(int reasonCode) {}


OSGi Services

System Services• Logging• Configuration Admin• Device Access• User Admin• IO Connector• Preferences• Component Runtime• Deployment Admin• Event Admin• Application Admin


Protocol Services• HTTP Service• UPnP Device Service• DMT Admin

Miscellaneous Services• Wire Admin• XML Parse• Measurement and State

Dependency Injection


References

• Acquiringo Event-based using bind/unbind methodso Lookup using ComponentContext

• Policyo Requiredo Optional

• Cardinalityo Singleo Multiple


References

public class GetAReference { @Reference ConnectionManager connMgr;}

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@Component@Servicepublic class LdapConnectionManager implements ConnectionManager { }

@Component@Servicepublic class JdbcConnectionManager implements ConnectionManager { }


Single Instance Reference

// OPTIONAL_UNARY == "0..1"// MANDATORY_UNARY == "1..1"

@Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY, policy = ReferencePolicy.STATIC)ConnectionManager connMgr;

protected void bindConnMgr(ConnectionManager mgr) { this.connMgr = mgr;}

protected void unbindConnMgr(ConnectionManager mgr) { this.connMgr = null;}


Multiple Instance Reference

// OPTIONAL_MULTIPLE == "0..n"// MANDATORY_MULTIPLE == "1..n"

@Reference(cardinality = ReferenceCardinality.OPTIONAL_MULTIPLE, policy = ReferencePolicy.DYNAMIC, referenceInterface = ConnectionManager.class, bind = "bindManager", unbind = "unbindManager")List<ConnectionManager> managers; // be sure to instantiate this

protected void bindManager(ConnectionManager mgr) { managers.add(mgr);}

protected void unbindManager(ConnectionManager mgr) { managers.remove(mgr);}


Reference Target

@ReferencePooledConnectionManager connMgr; //boo!

@Reference(target = "(type=pooled)")ConnectionManager connMgr; //yay!

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@Component @Service@Property(name = "type", value = "simple")public class SimpleCM implements ConnectionManager {}

@Component @Service@Property(name = "type", value = "pooled")public class PooledCM implements ConnectionManager {}


Configuration


Felix Admin Console


New Service Configuration

@ReferenceConfigurationAdmin cfgAdmin;

@Activateprotected void activate() { Configuration cfg = cfgAdmin.createFactoryConfiguration("some.factory.pid");

Hashtable props = new Hashtable(); props.put("key1", "val1"); props.put("key2", "val2");

config.update(props);}


Configure A Reference

@ReferenceConnectionManager connMgr;

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@ReferenceConfigurationAdmin cfgAdmin;

@Activateprotected void activate() { Configuration cfg = cfgAdmin.createFactoryConfiguration("some.factory.pid");

Hashtable props = new Hashtable(); props.put("connMgr.target", "(type=pooled)");

config.update(props);}


Technology

Using OSGi in Nakamura