org.osgi.service.device
Interface Driver

public interface Driver

A Driver service object must be registered by each Driver bundle wishing to attach to Device services provided by other drivers. For each newly discovered Device object, the device manager enters a bidding phase. The Driver object whose match(org.osgi.framework.ServiceReference) method bids the highest for a particular Device object will be instructed by the device manager to attach to the Device object.

See Also:

Device, DriverLocator

Method Summary

java.lang.String	attach(ServiceReference reference) Attaches this Driver service to the Device service represented by the given ServiceReference object.
int	match(ServiceReference reference) Checks whether this Driver service can be attached to the Device service.

Method Detail

match

public int match(ServiceReference reference)
          throws java.lang.Exception

Checks whether this Driver service can be attached to the Device service. The Device service is represented by the given ServiceReference and returns a value indicating how well this driver can support the given Device service, or Device.MATCH_NONE if it cannot support the given Device service at all.

The return value must be one of the possible match values defined in the device category definition for the given Device service, or Device.MATCH_NONE if the category of the Device service is not recognized.

In order to make its decision, this Driver service may examine the properties associated with the given Device service, or may get the referenced service object (representing the actual physical device) to talk to it, as long as it ungets the service and returns the physical device to a normal state before this method returns.

A Driver service must always return the same match code whenever it is presented with the same Device service.

The match function is called by the device manager during the matching process.

Parameters:

reference - the ServiceReference object of the device to match

Returns:

value indicating how well this driver can support the given Device service, or Device.MATCH_NONE if it cannot support the Device service at all

Throws:

java.lang.Exception - if this Driver service cannot examine the Device service

attach

public java.lang.String attach(ServiceReference reference)
                        throws java.lang.Exception

Attaches this Driver service to the Device service represented by the given ServiceReference object.

A return value of null indicates that this Driver service has successfully attached to the given Device service. If this Driver service is unable to attach to the given Device service, but knows of a more suitable Driver service, it must return the DRIVER_ID of that Driver service. This allows for the implementation of referring drivers whose only purpose is to refer to other drivers capable of handling a given Device service.

After having attached to the Device service, this driver may register the underlying device as a new service exposing driver-specific functionality.

This method is called by the device manager.

Parameters:

reference - the ServiceReference object of the device to attach to

Returns:

null if this Driver service has successfully attached to the given Device service, or the DRIVER_ID of a more suitable driver

Throws:

java.lang.Exception - if the driver cannot attach to the given device and does not know of a more suitable driver