org.demac.transport
Class TransportService

java.lang.Object
  org.demac.transport.TransportService

All Implemented Interfaces:

Service

Direct Known Subclasses:

FluctNetTransportService, OldTransportServiceImpl, TransportServiceImpl

public abstract class TransportService
extends java.lang.Object
implements Service

This class represents the transport layer of the DEMAC framework. It provides an asynchronous message delivering service and abstracts from the used delivering mechanism like TCP/IP, Bluetooth etc. The addressing schema basis on handles for devices and messages. The transport service selects one of the available lower transport services which are associated with the receiving device. Sent and received messages are implementations of the TransportMessage interface. To be notified of incomming messages the interested object must implement the org.demac.transport.TransportListener interface and register itself at the transport service.

The transport service also provides methods to inquire DEMAC devices in the neighbourhood.

Constructor Summary

TransportService()

Method Summary

abstract void	addDevice(Device device) Method to add a device manually to the transport service.
abstract void	addTransportListener(TransportListener listener) Method to register an object which implements the org.demac.transport.TransportListener interface at the service.
abstract void	detectDevices() Method to start the inquiary for devices in the neigbourhood.
abstract TransportMessage	extractMessage(MessageHandle handle) Method to get a message from the transport service which has arrived from foreign devices and remove it immediately.
abstract java.util.Enumeration	getAllDevices() Method to get all devices which are known by the transport service.
abstract DeviceHandle	getLocalDeviceHandle() Method to get the org.demac.transport.DeviceHandle of the local device.
abstract java.lang.String	getLocalName() Method to get a user-friendly name of the local device.
static TransportService	getTransportService() Method to get an instance of the DEMAC transport service.
abstract TransportMessage	receiveMessage(MessageHandle handle) Method to get a message from the the transport service which has arrived from foreign devices.
abstract void	removeDevice(Device device) Method to remove a device manually from the transport service.
abstract void	removeMessage(MessageHandle handle) Method to remove a message from the transport service.
abstract void	removeTransportListener(TransportListener listener) Method to remove a registered listener from the transport service.
abstract void	sendMessage(TransportMessage msg) Method to send a message to a device.
abstract void	sendMessage(TransportMessage msg, Constraint[] constraints) Method to send a message to a device under a set of constraints.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.demac.Service

isStarted, start, stop

Constructor Detail

TransportService

public TransportService()

Method Detail

getTransportService

public static TransportService getTransportService()

Method to get an instance of the DEMAC transport service. As mobile devices are mostly limited in their computing power the TransportService should be implemented as a singleton. This method should provide access to the instance of the transport service.

Returns:

the instance of the transport service.

getAllDevices

public abstract java.util.Enumeration getAllDevices()
                                             throws TransportException

Method to get all devices which are known by the transport service.

Returns:

an enumeration of org.demac.transport.Device[s]

Throws:

TransportException - if the service has not been started before invoking this method

detectDevices

public abstract void detectDevices()
                            throws TransportException

Method to start the inquiary for devices in the neigbourhood.

Throws:

TransportException - if the inquiary can not be started

sendMessage

public abstract void sendMessage(TransportMessage msg)
                          throws TransportException

Method to send a message to a device. The message must be an implementation of the org.demac.transport.TransportMessage interface. Sender, receiver and the message itself are referenced in the message.

Parameters:

msg - the message which is to be sent

Throws:

TransportException - if the message can not be sent of if the service has not been started.

sendMessage

public abstract void sendMessage(TransportMessage msg,
                                 Constraint[] constraints)
                          throws TransportException

Method to send a message to a device under a set of constraints. The message must be an implementation of the org.demac.transport.TransportMessage interface and the set of constraints is build up of implementations of the org.demac.transport.Constraint interface. Sender, receiver and the message itself are referenced in the message.

Parameters:

msg - the message which is to be sent

constraints - the set of constraints to fulfill

Throws:

TransportException - if the message can not be sent

addTransportListener

public abstract void addTransportListener(TransportListener listener)

Method to register an object which implements the org.demac.transport.TransportListener interface at the service.

Parameters:

listener - the listener which is to be registerd

removeTransportListener

public abstract void removeTransportListener(TransportListener listener)

Method to remove a registered listener from the transport service.

Parameters:

listener - the listener which is to be removed

receiveMessage

public abstract TransportMessage receiveMessage(MessageHandle handle)
                                         throws MessageNotAvailableException

Method to get a message from the the transport service which has arrived from foreign devices. The reference for the message can be obtained via the org.demac.transport.TransportListener interface.

Parameters:

handle - the reference of the message

Returns:

the message associated with the org.demac.transport.MessageHandle

Throws:

MessageNotAvailableException - if the message is not available (any more)

removeMessage

public abstract void removeMessage(MessageHandle handle)
                            throws MessageNotAvailableException

Method to remove a message from the transport service. The reference to the message can be obtained via the org.demac.transport.TransportListener interface.

Parameters:

handle - the org.demac.transport.MessageHandleassociated to the message

Throws:

MessageNotAvailableException - if the message is not available (any more)

extractMessage

public abstract TransportMessage extractMessage(MessageHandle handle)
                                         throws MessageNotAvailableException

Method to get a message from the transport service which has arrived from foreign devices and remove it immediately. Can be seen as a combination of receiveMessage(MessageHandle handle) and removeMessage(MessageHandle handle)

Parameters:

handle - the reference of the message

Returns:

the message associated with the org.demac.transport.MessageHandle

Throws:

MessageNotAvailableException - if the message is not available (any more)

getLocalDeviceHandle

public abstract DeviceHandle getLocalDeviceHandle()
                                           throws TransportException

Method to get the org.demac.transport.DeviceHandle of the local device.

Returns:

the handle of the local device

Throws:

TransportException - if the service has not been started before invoking this method

getLocalName

public abstract java.lang.String getLocalName()
                                       throws TransportException

Method to get a user-friendly name of the local device.

Returns:

the name of the local device

Throws:

TransportException - if the service has not been started before invoking this method

addDevice

public abstract void addDevice(Device device)
                        throws TransportException

Method to add a device manually to the transport service.

Parameters:

device - the device which is to be registered

Throws:

TransportException - if the service has not been started before invoking this method

removeDevice

public abstract void removeDevice(Device device)
                           throws TransportException

Method to remove a device manually from the transport service.

Parameters:

device - the device which is to be removed

Throws:

TransportException - if the service has not been started before invoking this method