org.osgi.service.wireadmin

Interface Consumer

public interface Consumer

Data Consumer, a service that can receive updated values from Producer services.

Service objects registered under the Consumer interface are expected to consume values from a Producer service via a Wire object. A Consumer service may poll the Producer service by calling the Wire.poll() method. The Consumer service will also receive an updated value when called at it's updated(Wire, Object) method. The Producer service should have coerced the value to be an instance of one of the types specified by the Wire.getFlavors() method, or one of their subclasses.

Consumer service objects must register with a service.pid and a WireConstants.WIREADMIN_CONSUMER_FLAVORS property. It is recommended that Consumer service objects also register with a service.description property.

If an Exception is thrown by any of the Consumer methods, a WireAdminEvent of type WireAdminEvent.CONSUMER_EXCEPTION is broadcast by the Wire Admin service.

Security Considerations - Data consuming bundles will require ServicePermission[Consumer,REGISTER]. In general, only the Wire Admin service bundle should have this permission. Thus only the Wire Admin service may directly call a Consumer service. Care must be taken in the sharing of Wire objects with other bundles.

Consumer services must be registered with their scope when they can receive different types of objects from the Producer service. The Consumer service should have WirePermission for each of these scope names.

Author:

$Id: 2f7f64f305e997fa2c381842b037057116dc3e07 $

Method Summary

Methods

Modifier and Type	Method and Description
void	producersConnected(Wire[] wires) Update the list of Wire objects to which this Consumer service is connected.
void	updated(Wire wire, java.lang.Object value) Update the value.

Method Detail

updated

void updated(Wire wire,
           java.lang.Object value)

Update the value. This Consumer service is called by the Wire object with an updated value from the Producer service.

Note: This method may be called by a Wire object prior to this object being notified that it is connected to that Wire object (via the producersConnected(Wire[]) method).

When the Consumer service can receive Envelope objects, it must have registered all scope names together with the service object, and each of those names must be permitted by the bundle's WirePermission. If an Envelope object is delivered with the updated method, then the Consumer service should assume that the security check has been performed.

Parameters:

wire - The Wire object which is delivering the updated value.

value - The updated value. The value should be an instance of one of the types specified by the Wire.getFlavors() method.

producersConnected

void producersConnected(Wire[] wires)

Update the list of Wire objects to which this Consumer service is connected.

This method is called when the Consumer service is first registered and subsequently whenever a Wire associated with this Consumer service becomes connected, is modified or becomes disconnected.

The Wire Admin service must call this method asynchronously. This implies that implementors of Consumer can be assured that the callback will not take place during registration when they execute the registration in a synchronized method.

Parameters:

wires - An array of the current and complete list of Wire objects to which this Consumer service is connected. May be null if the Consumer service is not currently connected to any Wire objects.