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Re: [ecf-dev] Fun with remote services part 1

Hi Eugen,

Eugen Reiswich wrote:
Hi Scott,

sure! The first problem I ran into was that (as you have explained recently) DS does not support providing authentication information. Due to that I had to create the ECF-IContainer instance programmatically. Afterwards I registered this instance as an OSGi service. Next, I've provided for the services I wanted to publish the following properties (the second one was a guess):
<property name="service.exported.interfaces" type="String" value="*"/>
<property name="service.exported.configs" type="String" value="ecf.xmpp.smack"/>


I did not provide the server URL as my IContainer was already connected so I didn't see any sense to do it here again. As soon as I started my application ECF threw an exception that there was a problem with a container. I did not know how to fix the problem. Unfortunately I can't reproduce the error because I've already changed my code. So the server side did not work so far.

To figure out what went wrong here, some sort of indication of what method call resulted in the exception...and ideally a stack trace would be needed. Without this, it's impossible to tell whether the problem was initiated by your code, something in ECF, or DS, or some interaction.



Client-Side: I did not understand how I can connect to my XMPP server client-side using DS. As far as I understand again I would have to do this programmatically (create IContainer, register in the client side service registry) because of the authentication information. Next, in order to be able to use a remote service in my RCP application I didn't understand how I can retrieve the appropriate remote service. I've tried to do it the way you've shown me, just to ask the service registry for a service using DS. But I got a NP - well how should the registry know that I require a service instance running on a different machine? So this didn't work either.

Where/in what code do you get a NPE? As per above, more info would be needed to determine whether such a problem is with your code, in DS, ECF, or in some interaction.


WRT your question about registry knowing that you require a service instance running on a different machine...as per the OSGi 4.2 remote services spec, on the consumer proxy there is a standard service property set...that service property is: "service.imported". On the *proxy*, this service property will be set to some non-null value. In ECF's implementation, this property is set to the IRemoteService instance associated with the proxy.

With a ServiceTracker, you can set up a filter that only detects/tracks service registry entries that have the 'service.imported' service property set to a non-null value. There's an example of doing this in this class: org.eclipse.ecf.internal.examples.remoteservices.hello.consumer.HelloConsumerApplication

With DS, you can get at the service properties for an injected service (via bind method) by exposing a bind method with the following signature:

void <bindMethodName>(ServiceReference svcReference)
e.g.
void bindHello(ServiceReference helloReference) {
...examine helloReference properties...to see if 'service.imported' is set...if it is, then you want it...if not then not
}


It's also possible to have the bind method use a signature like this

void bindHello(IHello hello, Map svcProperties)

This is as specified in the DS specification, section 112.3.1 in the OSGi 4.2 compendium spec.


And as you mentioned I started to read articles that were outdated and hence used an old API. Furthermore I've found some ECF/DS examples that only work in a local subnet but didn't find any example with ECF, DS and XMPP.

Do you mean the hello examples? Yes, these use the ECF generic and DS rather than the XMPP provider. Unfortunately, we simply don't have enough resources to create examples with all combinations of providers...crossed with the use of DS or not.



Well now I'll wait for an article or tutorial that could help me. I don't think I'll solve my problems without on site guidance.

I'm not sure that waiting for someone else to create an article or tutorial that has this specific combination of technologies for your use case (i.e. OSGi remote services, DS, and XMPP provider) is a great idea...as although I and some others could certainly do it, without some support several of us don't have the means to do it specifically for this one use case...given the other docs, examples, combinations of technologies that have been/are being requested.


If you want something like this (article, tutorial, working example code, etc) specifically for your use case, it would be best, I think, to either contribute to creating it, support (via some means) someone else in doing so, or some combination of both.

Scott