You are viewing a plain text version of this content. The canonical link for it is here.
Posted to users@felix.apache.org by MMatos <ra...@gmail.com> on 2007/09/12 00:28:25 UTC
java.lang.ClassNotFoundException when using reflection ?
Hello!
I've been playing with apache felix for some months. Now I am building
a bundle that depends on external jars and use a bit of reflection.
To overcome the problem of the external library I have used the
Bundle-ClassPath: manifest header.
Currently my problem is when I tried to load a class using reflection
and I get a class not found exception.
javax.management.ReflectionException: The MBean class could not be
loaded by the default loader repository
at
com.sun.jmx.mbeanserver.MBeanInstantiatorImpl.findClassWithDefaultLoaderRepository(MBeanInstantiatorImpl.java:61)
at
com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.createMBean(DefaultMBeanServerInterceptor.java:271)
at
com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.createMBean(DefaultMBeanServerInterceptor.java:211)
at
com.sun.jmx.mbeanserver.JmxMBeanServer.createMBean(JmxMBeanServer.java:408)
at kAdapt.mbeanServer.MainServer.registerMBean(MainServer.java:131)
Caused by: java.lang.ClassNotFoundException: kAdapt.mbeanServer.InfoMBean
at
com.sun.jmx.mbeanserver.ClassLoaderRepositorySupport.loadClass(ClassLoaderRepositorySupport.java:208)
at
com.sun.jmx.mbeanserver.ClassLoaderRepositorySupport.loadClass(ClassLoaderRepositorySupport.java:128)
at
com.sun.jmx.mbeanserver.MBeanInstantiatorImpl.findClassWithDefaultLoaderRepository(MBeanInstantiatorImpl.java:58)
... 18 more
The class in question kAdapt.mbeanServer.InfoMBean is of course in the
package hierarchy but the osgi classloader seems to miss it ...
I would like to know why this happens and the solution.
( In this particular problem the class failing to load is an MBean when
trying to create it
-->> at
com.sun.jmx.mbeanserver.MBeanInstantiatorImpl.findClassWithDefaultLoaderRepository(MBeanInstantiatorImpl.java:61)
but I think that this problem will happen whenever one uses reflection
... Am I right ?
)
I tried with DynamicImport-Package but without success too ...
Here is my manifest
Manifest-Version: 1.0
Archiver-Version: Plexus Archiver
Created-By: Apache Maven
Build-Jdk: 1.5.0_12
Bundle-Activator: kAdapt.Activator
DynamicImport-Package: kAdapt.mbeanServer <<---- the class not found
is here
Bundle-ClassPath: .,kAdapt,js-1.6R5.jar
Import-Package: org.osgi.framework;version=1.3,org.osgi.service.log;ve
rsion=1.3,javax.management.remote,javax.management,javax.xml.parsers,
org.w3c.dom,org.xml.sax
Bundle-ManifestVersion: 2
Any guidance will be greatly appreciated.
Miguel Matos
PS: I think I could use the jmx facilities provided by felix ( I am
already doing that in another bundle, but that is not the point in my
question....))
---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscribe@felix.apache.org
For additional commands, e-mail: users-help@felix.apache.org
Re: java.lang.ClassNotFoundException when using reflection ?
Posted by Felix Meschberger <fm...@gmail.com>.
Hi Miguel,
Alright, so I assume this case is closed.
Regards and have a nice day
Felix
Am Mittwoch, den 12.09.2007, 13:02 +0100 schrieb Miguel Matos:
> Hi again,
>
> Felix Meschberger wrote:
> > Hi Migueal,
> >
> > Am Mittwoch, den 12.09.2007, 11:46 +0100 schrieb Miguel Matos:
> >
> > > > So you would have to make sure the JMX
> > > > Server knows about how to load the MBeans from within the Bundles -
> > > > given that Bundles may come and go, this sounds like tricky. Generally I
> > > > try no to use the JMX Server to create MBeans because of these issues.
> > > >
> > > >
> > > How do you create the MBeans ?
> > >
> >
> > Generally, I have my internal services and state objects, which register
> > themselves with the JMX Server, either directly or using some
> > ProxyMBean.
> >
> > But I have to admit, that I never had a requirement to have the
> > JMX-based administrator create MBeans - and when there was the slightest
> > chance, there could be such a requirement, I quickly found a
> > workaround :-)
> >
> >
> Well that is what I did ;) Instead of having the jmx server create
> the MBeans I create them as a normal obejct and then register them
> with the mbeanserver solving the problem of the classloading by the
> jmx side.
> The mbeans used are dynamic mbeans and there is no difference in
> creating them by jmx or by "hand" by the application and later
> registering them.
>
> > > As a side question is this a general problem when using reflection in
> > > a osgi environment?
> > >
> >
> > Reflection in itself is not the primary issue. The problem is tampering
> > with class loading. And this is somewhat involved if you come from the
> > traditional Java ClassLoader hierarchy model where each class loader
> > knows all classes of its ancestor class loaders.
> >
> > In OSGi environment, each bundle has its class loader which only asks
> > its parent class loader under certain circumstances (mainly
> > bootdelegation classes). Generally, a bundle class loader only knows
> > about its imports and the bundle-contained classes.
> >
> > One option to find solutions regarding class loaders and bundles might
> > be to implement a class loader along the lines of the Equinox
> > BundleProxyClassLoader recipe [1].
> >
> >
> Well I no longer need a custom classloader but I will have a look at
> the recipe to help me dive deeper in the inner workings of osgi ;)
>
> Thanks for your help
>
> Miguel Matos
> > Regards
> > Felix
> >
> > [1] http://wiki.eclipse.org/BundleProxyClassLoader_recipe
> >
> >
> > > Miguel Matos
> > >
> > > > Hope this helps.
> > > >
> > > > Regards
> > > > Felix
> > > >
> > > > Am Dienstag, den 11.09.2007, 23:28 +0100 schrieb MMatos:
> > > >
> > > >
> > > > > Hello!
> > > > >
> > > > > I've been playing with apache felix for some months. Now I am building
> > > > > a bundle that depends on external jars and use a bit of reflection.
> > > > >
> > > > > To overcome the problem of the external library I have used the
> > > > > Bundle-ClassPath: manifest header.
> > > > >
> > > > > Currently my problem is when I tried to load a class using reflection
> > > > > and I get a class not found exception.
> > > > >
> > > > >
> > > > > javax.management.ReflectionException: The MBean class could not be
> > > > > loaded by the default loader repository
> > > > > at
> > > > > com.sun.jmx.mbeanserver.MBeanInstantiatorImpl.findClassWithDefaultLoaderRepository(MBeanInstantiatorImpl.java:61)
> > > > > at
> > > > > com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.createMBean(DefaultMBeanServerInterceptor.java:271)
> > > > > at
> > > > > com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.createMBean(DefaultMBeanServerInterceptor.java:211)
> > > > > at
> > > > > com.sun.jmx.mbeanserver.JmxMBeanServer.createMBean(JmxMBeanServer.java:408)
> > > > > at kAdapt.mbeanServer.MainServer.registerMBean(MainServer.java:131)
> > > > >
> > > > >
> > > > > Caused by: java.lang.ClassNotFoundException: kAdapt.mbeanServer.InfoMBean
> > > > > at
> > > > > com.sun.jmx.mbeanserver.ClassLoaderRepositorySupport.loadClass(ClassLoaderRepositorySupport.java:208)
> > > > > at
> > > > > com.sun.jmx.mbeanserver.ClassLoaderRepositorySupport.loadClass(ClassLoaderRepositorySupport.java:128)
> > > > > at
> > > > > com.sun.jmx.mbeanserver.MBeanInstantiatorImpl.findClassWithDefaultLoaderRepository(MBeanInstantiatorImpl.java:58)
> > > > > ... 18 more
> > > > >
> > > > >
> > > > > The class in question kAdapt.mbeanServer.InfoMBean is of course in the
> > > > > package hierarchy but the osgi classloader seems to miss it ...
> > > > > I would like to know why this happens and the solution.
> > > > >
> > > > > ( In this particular problem the class failing to load is an MBean when
> > > > > trying to create it
> > > > > -->> at
> > > > > com.sun.jmx.mbeanserver.MBeanInstantiatorImpl.findClassWithDefaultLoaderRepository(MBeanInstantiatorImpl.java:61)
> > > > > but I think that this problem will happen whenever one uses reflection
> > > > > ... Am I right ?
> > > > > )
> > > > >
> > > > > I tried with DynamicImport-Package but without success too ...
> > > > >
> > > > > Here is my manifest
> > > > >
> > > > > Manifest-Version: 1.0
> > > > > Archiver-Version: Plexus Archiver
> > > > > Created-By: Apache Maven
> > > > > Build-Jdk: 1.5.0_12
> > > > > Bundle-Activator: kAdapt.Activator
> > > > > DynamicImport-Package: kAdapt.mbeanServer <<---- the class not found
> > > > > is here
> > > > > Bundle-ClassPath: .,kAdapt,js-1.6R5.jar
> > > > > Import-Package: org.osgi.framework;version=1.3,org.osgi.service.log;ve
> > > > > rsion=1.3,javax.management.remote,javax.management,javax.xml.parsers,
> > > > > org.w3c.dom,org.xml.sax
> > > > > Bundle-ManifestVersion: 2
> > > > >
> > > > > Any guidance will be greatly appreciated.
> > > > >
> > > > > Miguel Matos
> > > > >
> > > > > PS: I think I could use the jmx facilities provided by felix ( I am
> > > > > already doing that in another bundle, but that is not the point in my
> > > > > question....))
> > > > >
> > > > > ---------------------------------------------------------------------
> > > > > To unsubscribe, e-mail: users-unsubscribe@felix.apache.org
> > > > > For additional commands, e-mail: users-help@felix.apache.org
> > > > >
> > > > >
> > > > >
> > > > ---------------------------------------------------------------------
> > > > To unsubscribe, e-mail: users-unsubscribe@felix.apache.org
> > > > For additional commands, e-mail: users-help@felix.apache.org
> > > >
> > > >
> > > >
> > > >
> > > ---------------------------------------------------------------------
> > > To unsubscribe, e-mail: users-unsubscribe@felix.apache.org For
> > > additional commands, e-mail: users-help@felix.apache.org
> > >
> >
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: users-unsubscribe@felix.apache.org
> > For additional commands, e-mail: users-help@felix.apache.org
> >
> >
> >
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@felix.apache.org For
> additional commands, e-mail: users-help@felix.apache.org
---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscribe@felix.apache.org
For additional commands, e-mail: users-help@felix.apache.org
Re: java.lang.ClassNotFoundException when using reflection ?
Posted by Felix Meschberger <fm...@gmail.com>.
Hi Migueal,
Am Mittwoch, den 12.09.2007, 11:46 +0100 schrieb Miguel Matos:
> > So you would have to make sure the JMX
> > Server knows about how to load the MBeans from within the Bundles -
> > given that Bundles may come and go, this sounds like tricky. Generally I
> > try no to use the JMX Server to create MBeans because of these issues.
> >
> How do you create the MBeans ?
Generally, I have my internal services and state objects, which register
themselves with the JMX Server, either directly or using some
ProxyMBean.
But I have to admit, that I never had a requirement to have the
JMX-based administrator create MBeans - and when there was the slightest
chance, there could be such a requirement, I quickly found a
workaround :-)
> As a side question is this a general problem when using reflection in
> a osgi environment?
Reflection in itself is not the primary issue. The problem is tampering
with class loading. And this is somewhat involved if you come from the
traditional Java ClassLoader hierarchy model where each class loader
knows all classes of its ancestor class loaders.
In OSGi environment, each bundle has its class loader which only asks
its parent class loader under certain circumstances (mainly
bootdelegation classes). Generally, a bundle class loader only knows
about its imports and the bundle-contained classes.
One option to find solutions regarding class loaders and bundles might
be to implement a class loader along the lines of the Equinox
BundleProxyClassLoader recipe [1].
Regards
Felix
[1] http://wiki.eclipse.org/BundleProxyClassLoader_recipe
>
> Miguel Matos
> > Hope this helps.
> >
> > Regards
> > Felix
> >
> > Am Dienstag, den 11.09.2007, 23:28 +0100 schrieb MMatos:
> >
> > > Hello!
> > >
> > > I've been playing with apache felix for some months. Now I am building
> > > a bundle that depends on external jars and use a bit of reflection.
> > >
> > > To overcome the problem of the external library I have used the
> > > Bundle-ClassPath: manifest header.
> > >
> > > Currently my problem is when I tried to load a class using reflection
> > > and I get a class not found exception.
> > >
> > >
> > > javax.management.ReflectionException: The MBean class could not be
> > > loaded by the default loader repository
> > > at
> > > com.sun.jmx.mbeanserver.MBeanInstantiatorImpl.findClassWithDefaultLoaderRepository(MBeanInstantiatorImpl.java:61)
> > > at
> > > com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.createMBean(DefaultMBeanServerInterceptor.java:271)
> > > at
> > > com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.createMBean(DefaultMBeanServerInterceptor.java:211)
> > > at
> > > com.sun.jmx.mbeanserver.JmxMBeanServer.createMBean(JmxMBeanServer.java:408)
> > > at kAdapt.mbeanServer.MainServer.registerMBean(MainServer.java:131)
> > >
> > >
> > > Caused by: java.lang.ClassNotFoundException: kAdapt.mbeanServer.InfoMBean
> > > at
> > > com.sun.jmx.mbeanserver.ClassLoaderRepositorySupport.loadClass(ClassLoaderRepositorySupport.java:208)
> > > at
> > > com.sun.jmx.mbeanserver.ClassLoaderRepositorySupport.loadClass(ClassLoaderRepositorySupport.java:128)
> > > at
> > > com.sun.jmx.mbeanserver.MBeanInstantiatorImpl.findClassWithDefaultLoaderRepository(MBeanInstantiatorImpl.java:58)
> > > ... 18 more
> > >
> > >
> > > The class in question kAdapt.mbeanServer.InfoMBean is of course in the
> > > package hierarchy but the osgi classloader seems to miss it ...
> > > I would like to know why this happens and the solution.
> > >
> > > ( In this particular problem the class failing to load is an MBean when
> > > trying to create it
> > > -->> at
> > > com.sun.jmx.mbeanserver.MBeanInstantiatorImpl.findClassWithDefaultLoaderRepository(MBeanInstantiatorImpl.java:61)
> > > but I think that this problem will happen whenever one uses reflection
> > > ... Am I right ?
> > > )
> > >
> > > I tried with DynamicImport-Package but without success too ...
> > >
> > > Here is my manifest
> > >
> > > Manifest-Version: 1.0
> > > Archiver-Version: Plexus Archiver
> > > Created-By: Apache Maven
> > > Build-Jdk: 1.5.0_12
> > > Bundle-Activator: kAdapt.Activator
> > > DynamicImport-Package: kAdapt.mbeanServer <<---- the class not found
> > > is here
> > > Bundle-ClassPath: .,kAdapt,js-1.6R5.jar
> > > Import-Package: org.osgi.framework;version=1.3,org.osgi.service.log;ve
> > > rsion=1.3,javax.management.remote,javax.management,javax.xml.parsers,
> > > org.w3c.dom,org.xml.sax
> > > Bundle-ManifestVersion: 2
> > >
> > > Any guidance will be greatly appreciated.
> > >
> > > Miguel Matos
> > >
> > > PS: I think I could use the jmx facilities provided by felix ( I am
> > > already doing that in another bundle, but that is not the point in my
> > > question....))
> > >
> > > ---------------------------------------------------------------------
> > > To unsubscribe, e-mail: users-unsubscribe@felix.apache.org
> > > For additional commands, e-mail: users-help@felix.apache.org
> > >
> > >
> >
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: users-unsubscribe@felix.apache.org
> > For additional commands, e-mail: users-help@felix.apache.org
> >
> >
> >
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@felix.apache.org For
> additional commands, e-mail: users-help@felix.apache.org
---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscribe@felix.apache.org
For additional commands, e-mail: users-help@felix.apache.org
Re: java.lang.ClassNotFoundException when using reflection ?
Posted by Felix Meschberger <fm...@gmail.com>.
Hi Miguel,
>>From the stack trace, I assume you want to create an MBean using the JMX
Server. For this to work, the JMX Server of course has to have some
knowledge of the class loaders used. In plain old Java applications this
is not so big of an issue.
In OSGi frameworks, this is more involved: You would have to provide the
JMX Server some support in loading the classes, which is defined in the
JMX spec (and which escapes my mind currently of what is to be done, but
IIRC you would have to do some stuff with ClassLoaderRepository...)
I assume, your JMX Server is running in the Java VM environment and your
MBean is located in the Bundle. So you would have to make sure the JMX
Server knows about how to load the MBeans from within the Bundles -
given that Bundles may come and go, this sounds like tricky. Generally I
try no to use the JMX Server to create MBeans because of these issues.
Finally, you say "external library" and refer to the Bundle-Classpath
manifest header. This sounds like a misconception: The Bundle-Classpath
lists additional locations, jar files generally, inside the bundle,
which should be used to build to the class loader for the bundle.
External Libraries are referred to by Import-Package headers and must be
provided by other bundles (through their Export-Package headers) or by
the org.osgi.framework.system.packages or
org.osgi.framework.bootdelegation system properties.
Hope this helps.
Regards
Felix
Am Dienstag, den 11.09.2007, 23:28 +0100 schrieb MMatos:
> Hello!
>
> I've been playing with apache felix for some months. Now I am building
> a bundle that depends on external jars and use a bit of reflection.
>
> To overcome the problem of the external library I have used the
> Bundle-ClassPath: manifest header.
>
> Currently my problem is when I tried to load a class using reflection
> and I get a class not found exception.
>
>
> javax.management.ReflectionException: The MBean class could not be
> loaded by the default loader repository
> at
> com.sun.jmx.mbeanserver.MBeanInstantiatorImpl.findClassWithDefaultLoaderRepository(MBeanInstantiatorImpl.java:61)
> at
> com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.createMBean(DefaultMBeanServerInterceptor.java:271)
> at
> com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.createMBean(DefaultMBeanServerInterceptor.java:211)
> at
> com.sun.jmx.mbeanserver.JmxMBeanServer.createMBean(JmxMBeanServer.java:408)
> at kAdapt.mbeanServer.MainServer.registerMBean(MainServer.java:131)
>
>
> Caused by: java.lang.ClassNotFoundException: kAdapt.mbeanServer.InfoMBean
> at
> com.sun.jmx.mbeanserver.ClassLoaderRepositorySupport.loadClass(ClassLoaderRepositorySupport.java:208)
> at
> com.sun.jmx.mbeanserver.ClassLoaderRepositorySupport.loadClass(ClassLoaderRepositorySupport.java:128)
> at
> com.sun.jmx.mbeanserver.MBeanInstantiatorImpl.findClassWithDefaultLoaderRepository(MBeanInstantiatorImpl.java:58)
> ... 18 more
>
>
> The class in question kAdapt.mbeanServer.InfoMBean is of course in the
> package hierarchy but the osgi classloader seems to miss it ...
> I would like to know why this happens and the solution.
>
> ( In this particular problem the class failing to load is an MBean when
> trying to create it
> -->> at
> com.sun.jmx.mbeanserver.MBeanInstantiatorImpl.findClassWithDefaultLoaderRepository(MBeanInstantiatorImpl.java:61)
> but I think that this problem will happen whenever one uses reflection
> ... Am I right ?
> )
>
> I tried with DynamicImport-Package but without success too ...
>
> Here is my manifest
>
> Manifest-Version: 1.0
> Archiver-Version: Plexus Archiver
> Created-By: Apache Maven
> Build-Jdk: 1.5.0_12
> Bundle-Activator: kAdapt.Activator
> DynamicImport-Package: kAdapt.mbeanServer <<---- the class not found
> is here
> Bundle-ClassPath: .,kAdapt,js-1.6R5.jar
> Import-Package: org.osgi.framework;version=1.3,org.osgi.service.log;ve
> rsion=1.3,javax.management.remote,javax.management,javax.xml.parsers,
> org.w3c.dom,org.xml.sax
> Bundle-ManifestVersion: 2
>
> Any guidance will be greatly appreciated.
>
> Miguel Matos
>
> PS: I think I could use the jmx facilities provided by felix ( I am
> already doing that in another bundle, but that is not the point in my
> question....))
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@felix.apache.org
> For additional commands, e-mail: users-help@felix.apache.org
>
---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscribe@felix.apache.org
For additional commands, e-mail: users-help@felix.apache.org