Device Injection in iCasa Platform

The iCasa platform provides a development and access model to build digital home applications, in this model, applications must be created using the iPOJO component model and packaged into OSGi deployment packages.

In iCasa development model any component requiring access to platform devices must use the special annotation @RequiresDevice to indicate the platform its requirement. The platform is charged of watch if the application has rights on devices, and injects device dependencies into the component.

The @RequiresDevice annotation must specify a unique identifier, the id attribute. It must also specify the utilization mode in the type attribute, it can be field, bind or unbind. If the type is field, the device is injected in a field, bind or unbind is used in methods as callbacks when the device is injected to the component or removed from it.

In the next example the component LightFollowMeApplication requires a set of devices of type PowerSwitch. In addition, two callbacks methods are indicate to bind and unbind operation, the RequiresDevice annotation is also used but type indicate are bind and unbind respectively.

  @Component(name="LightFollowMeApplication")
  @Instantiate
  public class LightFollowMeApplication extends EmptyDeviceListener {

      /** Field for powerSwitches dependency */
      @RequiresDevice(id="powerSwitches", type="field", optional=true)
      private PowerSwitch[] powerSwitches;

      /** Bind Method for powerSwitches dependency */
      @RequiresDevice(id="powerSwitches", type="bind")
      public void bindPowerSwitch(PowerSwitch powerSwitch, Map properties) {
          powerSwitch.addListener(this);
      }

      /** Unbind Method for powerSwitches dependency */
      @RequiresDevice(id="powerSwitches", type="unbind")    
      public void unbindPowerswitch(PowerSwitch powerSwitch, Map properties) {
          powerSwitch.removeListener(this);
      }
  }