org.eclipse.scada.da.server.common

Class DataItemBase

java.lang.Object

org.eclipse.scada.da.server.common.DataItemBase

All Implemented Interfaces:

DataItem

Direct Known Subclasses:

DataItemBaseChained, DataItemInput, DataItemOutput, DataItemTargetImpl, MemoryDataItem

public abstract class DataItemBase
extends Object
implements DataItem

This is an abstract base class for the DataItem interface. It also supports the SuspendableDataItem interface.

Author:

Jens Reimann <jens.reimann@th4-systems.com>

See Also:

SuspendableDataItem

Field Summary

Fields

Modifier and Type	Field and Description
protected ItemListener	listener

Constructor Summary

Constructors

Constructor and Description
DataItemBase(DataItemInformation information)

Method Summary

Modifier and Type	Method and Description
protected Map<String,Variant>	getCacheAttributes()
protected Variant	getCacheValue()
DataItemInformation	getInformation()
protected void	handleListenerChange(ItemListener listener)
protected void	notifyData(Variant value, Map<String,Variant> attributes) Notify a data change without checking for a real change.
void	notifyData(Variant value, Map<String,Variant> attributes, boolean cache) Notify a data change without checking for a real change.
void	setListener(ItemListener listener) Sets the listener for this item.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.eclipse.scada.da.server.common.DataItem

getAttributes, readValue, startSetAttributes, startWriteValue

Field Detail

listener

protected ItemListener listener

Constructor Detail

DataItemBase

public DataItemBase(DataItemInformation information)

Method Detail

getInformation

public DataItemInformation getInformation()

Specified by:

getInformation in interface DataItem

setListener

public void setListener(ItemListener listener)

Description copied from interface: DataItem

Sets the listener for this item. Set by the controller to which this item is registered. The item has to use the listener provided.

Specified by:

setListener in interface DataItem

Parameters:

listener - The listener to use or null to disable notification

handleListenerChange

protected void handleListenerChange(ItemListener listener)

getCacheValue

protected Variant getCacheValue()

getCacheAttributes

protected Map<String,Variant> getCacheAttributes()

notifyData

protected void notifyData(Variant value,
                          Map<String,Variant> attributes)

Notify a data change without checking for a real change.

See notifyData(Variant, Map, boolean) when and how to use the method!

Parameters:

value - the value to send

attributes - the attributes to send

notifyData

public void notifyData(Variant value,
                       Map<String,Variant> attributes,
                       boolean cache)

Notify a data change without checking for a real change.

This method simply forwards the change notification to the currently connected listener. It does not provide any real difference check and should therefore only be called by implementations that check for difference first.

If you simple want to send data away without the need to check for differences first see DataItemBaseChained, DataItemInput or one of their derivations.

Parameters:

value - the value to send

attributes - the attributes to send

cache - cache bit