Service

Add the appropriate child element (, or ) to the section of the plugin.xml file.

For the newly added child element, set the following attributes:
- serviceInterface: specifies the service interface class.
- serviceImplementation: specifies the service implementation class.

Note that the interface and implementation classes can be the same.To clarify the service declaration procedure, consider the following fragment of the plugin.xml file:

<extensions defaultExtensionNs="com.intellij">
  <!-- Declare the application level service -->
  <applicationService serviceInterface="Mypackage.MyServiceInterfaceClass" serviceImplementation="Mypackage.MyServiceImplClass" />

  <!-- Declare the project level service -->
  <projectService serviceInterface="Mypackage.MyProjectServiceInterfaceClass" serviceImplementation="Mypackage.MyProjectServiceImplClass" />
</extensions>

Get

To instantiate your service, in Java code, use the following syntax:

MyServiceImplClass service = ServiceManager.getService(MyServiceImplClass.class);

Documentation / Reference

http://www.jetbrains.org/intellij/sdk/docs/basics/plugin_structure/plugin_services.html