Hi Yashodhan,
>
> I have created a set of services and a plugin based on mitkCoreServices
> (org.mitk.core.services). My understanding of the
> mitkCoreServicesPlugin is that it serves to start the
> DataStorageService.
A more suited terminology would be that it "registers" the DataStorageService.
If you are considering to execute cpu-intensive code inside the constructor of
a service, you may want to defer the execution of this code until a service
consumer calls a method on your service implementation. Otherwise, application
startup may be delayed considerably.
> I was wondering how this plugin is linked with or called from the main
> application? I was hoping for a mechanism where a user could start
> different plugins that would start different services. Does something
> like this exist?
>
All MITK plugins depend (may be implicitly) on org.mitk.core.services. You can
introduce plug-in dependencies by writing something like
Require-Bundle: org.mitk.core.services, ...
In your plugins MANIFEST.MF file. This ensures that all dependencies are loaded
and started.
If you have a set of plugins implementing different service interfaces, you can
use your plugins IBundleContext (you can get it from inside your
IBundleActivator::Start() method) to start a specific plugin (which would than
register a service class). For example (untested):
// your IBundleContext
berry::IBundleContext::Pointer context = ...
berry::IBundle::ConstPointer cplugin =
context->FindBundle("my.fancy.service.plugin");
// unfortunately, this is needed due to a design problem (I think)
berry::IBundle::Pointer plugin =
berry::IBundle::Pointer(const_cast<berry::IBundle*>(plugin.GetPointer()));
plugin->Start();
MyFancyService::Pointer fancyService =
context->GetService<MyFancyService>("my.fancy.service");
This approach allows you decouple the service interface and the implementation,
if you want. For example:
Plugin A: contains a "service interface" IMyFancyService
Plugin B: implements IMyFancyService in MyFancyImpl (Require-Bundle: A)
Plugin C: uses IMyFancyService (Require-Bundle: A) by starting the concrete
implementation via context->FindBundle("B")...
If loading your service implementation plugins is cheap, you can also "force"
their loading on application startup, by writing:
Bundle-ActivationPolicy: eager
In their MANIFEST.MF file. This way, you don't need to manually start the
plugins. Note that registering different implementations for the same service
id is not (yet) supported. You would get a Poco::ExistsException thrown.
Hope this helps,
Sascha
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