org.eclipse.scada.hd

Interface QueryListener

All Known Implementing Classes:

QueryControlView, QueryDataView, QueryHandler, QueryHandler, QueryImpl, QueryImpl.QueryEntry, QueryViewPart

public interface QueryListener

A query listener interface

The query listener is called by the Query to notify the listener of internal changes in the query. In most cases the creator of the query is interested in receiving the query results.

The updateState(QueryState) method may be called at any time by the query and is only for informational purposes. The query can switch the status without request from the client back to QueryState.LOADING for example although the client did not request a change in parameters. The query should however update the status only if necessary and use the state QueryState.LOADING as an indicator that data is being fetched from the archive and that values still need to be updated. It should use QueryState.COMPLETE as an indicator that all data was fetched from the archive. Data may still be updated in state QueryState.COMPLETE.

The the query is closed (and only then) the query must set the status to QueryState.DISCONNECTED.

Before any data is transmitted the method updateParameters(QueryParameters, Set) must be called including the actual parameters (although they might be the same as the requested parameters) and including all provided value types. Further calls to #updateData(int, Map, ValueInformation[]) must contain exactly these value types. After updateParameters(QueryParameters, Set) was called all previously known data is considered invalid.

Calls to #updateData(int, Map, ValueInformation[]) will provide new values. The call allows to split up data in packets. Queries should try to provide data as early as possible but still should group data in chunks to reduce update calls. The values must contain exactly the value types as announces by the previous call to updateParameters(QueryParameters, Set). All arrays sizes must have the same length for each call and must not exceed the announces entry size.

There must be no calls the listener after the query was closed and the final state change to QueryState.DISCONNECTED was send.

Since:

0.14.0

Author:

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

See Also:

Query

Method Summary

Methods

Modifier and Type	Method and Description
void	updateData(int index, Map<String,List<Double>> values, List<ValueInformation> valueInformation) Reports data update
void	updateParameters(QueryParameters parameters, Set<String> valueTypes) Reports a change in parameters
void	updateState(QueryState state) Updates the state of the query

Method Detail

updateState

void updateState(QueryState state)

Updates the state of the query

Parameters:

state - the new state

updateParameters

void updateParameters(QueryParameters parameters,
                    Set<String> valueTypes)

Reports a change in parameters

Parameters:

parameters - the new parameters, must not be null

valueTypes - the new value types to expect, must not be null or empty

updateData

void updateData(int index,
              Map<String,List<Double>> values,
              List<ValueInformation> valueInformation)

Reports data update

All arrays must have the same size.

Parameters:

index - index from which the data update starts, must be greater or equal to zero and lower than the reported number of entries

values - the values that are updates, must not be null

valueInformation - the value information for the provided values. must not be null