Receiving configuration data using the ManagedService interface

Liberty profile configuration is managed by the OSGi Configuration Admin service and can be accessed according to the OSGi Configuration Admin service specification. Sets of configuration properties are identified by a persisted identity (PID) used to associate an element in server.xml, where the PID is used as the element name, with a component that registers to receive the properties.

For an OSGi bundle whose lifecycle is managed using the BundleActivator interface, a straightforward way to receive the configuration properties is to implement the org.osgi.service.cm.ManagedService interface, which specifies the PID as one its properties.

Example

Remember:

1. In Eclipse, we must select an SPI target runtime from Window > Preferences > Plug-In Development > Target Platform.

2. Add the following statement to the MANIFEST.MF file:
   Import-Package: org.osgi.service.cm;version="1.5.0"

3. Press Ctrl + Shift + O to update the bundle activator.

In this example, the Activator class implements the ManagedService interface in addition to the BundleActivator interface, and receives configuration properties using the updated method. We can provide default property values to simplify what must be specified in the user configuration.

public class Activator implements BundleActivator, ManagedService {

  public void start(BundleContext context) throws Exception {
    System.out.println("Sample bundle starting");
    // register to receive configuration     ServiceRegistration<ManagedService> configRef = context.registerService(
      ManagedService.class,   this,   getDefaults()
      );
  }

  public void stop(BundleContext context) throws Exception {
    System.out.println("Sample bundle stopping");
    configRef.unregister();
  }

  Hashtable getDefaults() {
    Hashtable defaults = new Hashtable();
    defaults.put(org.osgi.framework.Constants.SERVICE_PID, "simpleBundle");
    return defaults;
  }

  public void updated(Dictionary<String, ?> properties) throws ConfigurationException {
    if (properties != null)
    {
      String configColor = (String) properties.get("color");
      String configFlavor = (String) properties.get("flavor");
    }
  }

}

User configuration for the bundle can optionally be provided in server.xml, or an included file, by the following entry:

<simpleBundle color="red" flavor="raspberry" />

The element name in the user configuration, simpleBundle matches the value of the org.osgi.framework.Constants.SERVICE_PID property used in the ManagedService registration.

For more advanced configuration use, see Describing configuration using the OSGi Metatype service.

Parent topic: Develop an OSGi bundle with simple activation