JAVA OSGi: InstantiationException with Declarative Services

I'm new to OSGi and am building a first DS-implementation.

开发者_开发百科Everything is coded according to "the book" but when running I get this error:

java.lang.InstantiationException: com.mine.logger.internal.udp.UdpListener
at java.lang.Class.newInstance0(Unknown Source)
at java.lang.Class.newInstance(Unknown Source)
at org.eclipse.equinox.internal.ds.model.ServiceComponent.createInstance(ServiceComponent.java:457)
at org.eclipse.equinox.internal.ds.model.ServiceComponentProp.createInstance(ServiceComponentProp.java:264)
at org.eclipse.equinox.internal.ds.model.ServiceComponentProp.build(ServiceComponentProp.java:325)
at org.eclipse.equinox.internal.ds.InstanceProcess.buildComponent(InstanceProcess.java:588)
at org.eclipse.equinox.internal.ds.InstanceProcess.buildComponents(InstanceProcess.java:196)
at org.eclipse.equinox.internal.ds.Resolver.getEligible(Resolver.java:328)
at org.eclipse.equinox.internal.ds.SCRManager.serviceChanged(SCRManager.java:221)
at org.eclipse.osgi.internal.serviceregistry.FilteredServiceListener.serviceChanged(FilteredServiceListener.java:104)
at org.eclipse.osgi.framework.internal.core.BundleContextImpl.dispatchEvent(BundleContextImpl.java:933)
at org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:227)
at org.eclipse.osgi.framework.eventmgr.ListenerQueue.dispatchEventSynchronous(ListenerQueue.java:149)
at org.eclipse.osgi.internal.serviceregistry.ServiceRegistry.publishServiceEventPrivileged(ServiceRegistry.java:756)
at org.eclipse.osgi.internal.serviceregistry.ServiceRegistry.publishServiceEvent(ServiceRegistry.java:711)
at org.eclipse.osgi.internal.serviceregistry.ServiceRegistrationImpl.register(ServiceRegistrationImpl.java:130)
at org.eclipse.osgi.internal.serviceregistry.ServiceRegistry.registerService(ServiceRegistry.java:206)
at org.eclipse.osgi.framework.internal.core.BundleContextImpl.registerService(BundleContextImpl.java:507)
at org.eclipse.equinox.internal.ds.InstanceProcess.registerService(InstanceProcess.java:504)
at org.eclipse.equinox.internal.ds.InstanceProcess.buildComponents(InstanceProcess.java:212)
at org.eclipse.equinox.internal.ds.Resolver.buildNewlySatisfied(Resolver.java:441)
at org.eclipse.equinox.internal.ds.Resolver.enableComponents(Resolver.java:213)
at org.eclipse.equinox.internal.ds.SCRManager.performWork(SCRManager.java:800)
at org.eclipse.equinox.internal.ds.SCRManager$QueuedJob.dispatch(SCRManager.java:767)
at org.eclipse.equinox.internal.ds.WorkThread.run(WorkThread.java:89)
at org.eclipse.equinox.internal.util.impl.tpt.threadpool.Executor.run(Executor.java:70)

This is the configuration.xml of the module I want to use in other ones:

<scr:component xmlns:scr="http://www.osgi.org/xmlns/scr/v1.1.0" activate="startup" deactivate="shutdown" immediate="true" name="com.mine.logger.storeindb">
   <implementation class="com.mine.logger.internal.storeindb.StoreLog"/>
   <service>
      <provide interface="com.mine.logger.storeindb.IStoreLog"/>
   </service>
</scr:component>

And this is the configuration.xml of the module which will use it:

<scr:component xmlns:scr="http://www.osgi.org/xmlns/scr/v1.1.0" name="com.mine.logger.udp">
   <implementation class="com.mine.logger.internal.udp.UdpListener"/>
   <reference bind="setStoreLog" interface="com.mine.logger.storeindb.IStoreLog" name="storelog" unbind="unsetStoreLog"/>
</scr:component>

Code for bind and unbind:

private IStoreLog storeLog;

public void setStoreLog(IStoreLog value)
{
    System.err.println("UdpListener > setStoreLog");
    this.storeLog = value;
}

public void unsetStoreLog(IStoreLog value)
{
    System.err.println("UdpListener > unsetStoreLog");
    if (this.storeLog == value) {
        this.storeLog = null;
    }
}

Any ideas? Thanks, Frank

InstantiationException:

Thrown when an application tries to create an instance of a class using the newInstance method in class Class, but the specified class object cannot be instantiated. The instantiation can fail for a variety of reasons including but not limited to:

• the class object represents an abstract class, an interface, an array class, a primitive type, or void
• the class has no nullary constructor

Is there a public, no-args constructor for com.mine.logger.internal.udp.UdpListener ?

Thanks to Thilo!

added a no-args function and error is gone!

public UdpListener() 
{
    // public, no-args constructor needed for Declarative Services !!!
}

public UdpListener(int port) 
{
    this.port = port;
}

Typo? The IStoreLog field is named storeLog but you say name="storelog" (lower-case l).

I had similar problem, caused by referencing non-public class. Something like:

in ServiceAImpl.java file:

class ServiceBImpl implements Service {
...
}

This was effect of unfortunate refactoring.