org.eclipse.scada.da.master

Interface MasterItemHandler

All Known Implementing Classes:

AbstractCommonHandlerImpl, AbstractConfigurableMasterHandlerImpl, AbstractMasterHandlerImpl, BlockHandlerImpl, CommonSumHandler, GenericRemoteMonitor, ManualHandlerImpl, MapperMasterHandler, MarkerHandlerImpl, MasterItemLogger, MultiMasterHandler, NegateHandlerImpl, RemoteBooleanAttributeAlarmMonitor, RemoteBooleanValueAlarmMonitor, RoundHandlerImpl, ScaleHandlerImpl, ScriptMonitor.InjectMasterHandler

public interface MasterItemHandler

Method Summary

Methods

Modifier and Type	Method and Description
void	dataUpdate(Map<String,Object> context, DataItemValue.Builder value) Called when data changed or the handler chain changed.
WriteRequestResult	processWrite(WriteRequest request) Handle a write request

Method Detail

dataUpdate

void dataUpdate(Map<String,Object> context,
              DataItemValue.Builder value)

Called when data changed or the handler chain changed.

The call gets a context object provided which each handler can use to store context information of one calculation run. Each calculation run gets a fresh new context. The context is intended to pass data from one handler to the next.

Although the value parameter is a mutable type, the handler may only make changes inside the dataUpdate method.

Parameters:

context - the context object

value - the changed value

processWrite

WriteRequestResult processWrite(WriteRequest request)

Handle a write request

This method is called when a master item received a write request. It will then pass on the request to all MasterItemHandler in order to process or alter the write request. Each handler returns a result and then the next handler will received that altered write request.

If null is returned instead of a new write result, original write request is used and it is considered that the handler has done nothing.

Parameters:

request - the write request to handle

Returns:

the resulting write request