A document on creating a consumer service.

A consumer service must implement and register the org.osgi.service.wireadmin.Consumer interface. It must have the following list of registration properties:

• org.osgi.framework.Constants.SERVICE_PID – The service PID of the consumer
• WireConstants.WIREADMIN_CONSUMER_FLAVORS – The consumed data object classes (flavors)
• WireConstants.WIREADMIN_CONSUMER_COMPOSITE – (Only for composite consumers) the service PIDs of the producers this service will communicate with
• WireConstants.WIREADMIN_CONSUMER_SCOPE – (Only for composite consumers) the list of descriptive data types consumed by the service.

The updated(Wire, Object) method of the consumer is responsible for actualizing the received data. It is called by the connected wires whenever new data is available. The producersConnected(Wire[]) method updates the list of connected wires if new wires are available, or already known wires are updated/removed.

A consumer service will be able to receive data only if there is at least one connected wire with a producer

The following simple example creates a consumer service ready to accept any data types. Its service PID is consumer.all.

Listing 1. Creating a simple consumer.

                    mport java.util.Hashtable;

import org.osgi.framework.BundleContext;
import org.osgi.framework.BundleActivator;
import org.osgi.framework.ServiceRegistration;
import org.osgi.framework.BundleException;
import org.osgi.service.wireadmin.*;

public class ConsumerImpl implements Consumer, BundleActivator {                
  private ServiceRegistration reg;

  public void start(BundleContext bc) throws BundleException {
    Hashtable prop = new Hashtable();
    //this property shows that the consumer will accept any data types
    prop.put(WireConstants.WIREADMIN_CONSUMER_FLAVORS, new Class[] {Object.class});
    //the identifier property of the consumer  
    prop.put("service.pid", "consumer.all");
    //registering the service on the framework
    reg = bc.registerService(Consumer.class.getName(), this, prop);    
  }
  
  public void stop(BundleContext bc) throws BundleException {
    reg.unregister();
  }
  
  /** Watches the list of wires*/
  public void producersConnected(Wire[] wires) {
    if (wires == null) {
      System.out.println("Not connected to any wires");
    } else {
      System.out.println("Connected to " + wires.length + " wires");
    }
  }
  
  /** Receives the new data whenever such are available */
  public void updated(Wire wire, Object value) {
    System.out.println("Updated " + wire + " with value " + value);
  }
  
}