On 1/25/10 17:22, Serge Merzliakov wrote:
Re felix.bundle.dictionary - this is the package which is contains the
dictionary implementation inside the bundle, and so I thought this is what
the bundle needs to export as its 'services offered'.
Yes, but the implementation must get the interface it is implementing
from the class path. In that tutorial example, the interface is packaged
in the same bundle as the implementation and the bundle doesn't import
the package. What you will want to do is take the service interface
package out of the impl bundle (or at a minimum, change its metadata so
it only imports it). Then add the package to the class path of your
application and export it from the system bundle using the
...system.packages property.
I am trying to see how a client of some kind (either a host application or
another bundle) uses a service provided by a bundle. From the samples, it
appears that an interface is created which is shared by client and bundle,
with the only catch being that both need to share the same Class<?> instance
(loaded from a common classloader - the hosts).
If a bundle just exports a package or service of which host app or other
bundles do not share a common interface (e.g. a dictionary service with no
interface known to client), then the only way to invoke it is to use the
reflection API.
I thought the way host and client share the same Class<?> instance was
through the config setup:
config.put(Constants.FRAMEWORK_SYSTEMPACKAGES_EXTRA,
"felix.bundle.dictionary.DictionaryService");
This just exposes classes already on the class path, but you have to put
them on the class path first. See above.
This example also shows an embedded cased:
http://felix.apache.org/site/apache-felix-application-demonstration.html
It actually works as a bundle or a stand-alone application.
-> richard
My ultimate goal is to create a set of java interfaces which have different
implementations inside OSGi bundles (1 implementation per bundle) and the
decision about which implementation (bundle) to load could be made at
runtime.
Serge
Richard S. Hall wrote:
Why are you making the felix.bundle.dictionary package available inside
from a bundle in the first place?
If you want to share packages between the host app and bundles inside
the framework, then these packages should be on the class path. There is
really no reason to include them packaged inside of bundles too.
-> richard
On 1/25/10 0:35, Serge Merzliakov wrote:
Hello,
I am having trouble with the OSGI tutorials, with the host
application
using a bundle service (Tutorial 2 - dictionary service). I have read
previous posts on classloader issues between host app and bundles and
also
read (apache-felix-framework-launching-and-embedding.html) page as well.
My problem is that despite trying to 'inject' the service interface class
from the host into the bundle, as detailed in Felix pages above, the
bundle
is still using its own service interface, causing the ClassCastException.
I
have shown this to be the case as if use:
Class<?> bundleInstance =
felix.getBundleContext().getBundle(1).loadClass("felix.bundle.dictionary.DictionaryService");
Object dictionary =
bundleInstance.cast(felix.getBundleContext().getService(ref))
then it works. I find this very 'clunky' and would much rather do:
DictionaryService dictionary = (DictionaryService)
felix.getBundleContext().getService(ref);
I have attached my host application and would appreciate any feeback as
to
how to solve the classloader issue (I have seen the HostActivator code,
and
tried it, but fail to see how that would solve my problem).
Serge
/***********************************************/
public static void main(String[] argv) throws Exception
{
System.out.println("\nWelcome to Felix.");
try
{
Properties config = new Properties();
config.setProperty(AutoProcessor.AUTO_DEPLOY_ACTION_PROPERY,
"install,start");
config.setProperty(AutoProcessor.AUTO_DEPLOY_DIR_PROPERY,
"/Users/serge/dev/osgi/Felix/bundle");
config.put(Constants.FRAMEWORK_SYSTEMPACKAGES_EXTRA,
"felix.bundle.dictionary.DictionaryService");
felix = getFrameworkFactory().newFramework(config);
felix.init();
AutoProcessor.process(config, felix.getBundleContext());
felix.start();
ServiceReference ref =
felix.getBundleContext().getServiceReference(DictionaryService.class.getName());
Class<?> hostClassInstance = DictionaryService.class; // hosts
version
Class<?> bundleClassInstance =
felix.getBundleContext().getBundle(1).loadClass("felix.bundle.dictionary.DictionaryService");
//bundle version
// -------- !!!!
// THIS LINE FAILS BECAUSE hostClassInstance !=
bundleClassInstance
DictionaryService svc = (DictionaryService)
felix.getBundleContext().getService(ref);
// ---------- !!!!
boolean found = svc.checkWord("hello");
System.out.println("word hello exists - " + found);
felix.waitForStop(4000);
felix.getBundleContext().ungetService(ref); //reference
counting
for bundle unloading
System.exit(0);
}
catch (Exception ex)
{
.......
}
}
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