org.opendaylight.mdsal.binding.api

Interface DataTreeChangeListener<T extends DataObject>

All Superinterfaces:

EventListener

All Known Subinterfaces:

ClusteredDataTreeChangeListener<T>

public interface DataTreeChangeListener<T extends DataObject>
extends EventListener

Interface implemented by classes interested in receiving notifications about data tree changes. It provides a cursor-based view of the change, which has potentially lower overhead and allow more flexible consumption of change event.

Method Summary

Modifier and Type	Method and Description
void	onDataTreeChanged(@NonNull Collection<DataTreeModification<T>> changes) Invoked when there was data change for the supplied path, which was used to register this listener.
default void	onInitialData() Invoked only once during registration of the listener if there was no data in the conceptual data tree for the supplied path, which was used to register this listener, and after this onDataTreeChanged(java.util.Collection<org.opendaylight.mdsal.binding.api.DataTreeModification<T>>) would always be invoked for data changes.

Method Detail

onDataTreeChanged

void onDataTreeChanged(@NonNull Collection<DataTreeModification<T>> changes)

Invoked when there was data change for the supplied path, which was used to register this listener.

This method may be also invoked during registration of the listener if there is any pre-existing data in the conceptual data tree for supplied path. This initial event will contain all pre-existing data as created.

Note: If there is no pre-existing data, the method onInitialData() will be invoked.

A data change event may be triggered spuriously, e.g. such that data before and after compare as equal. Implementations of this interface are expected to recover from such events. Event producers are expected to exert reasonable effort to suppress such events.

In other words, it is completely acceptable to observe a DataObjectModification, while the state observed before and after- data items compare as equal.

Parameters:

changes - Collection of change events, may not be null or empty.

onInitialData

default void onInitialData()

Invoked only once during registration of the listener if there was no data in the conceptual data tree for the supplied path, which was used to register this listener, and after this onDataTreeChanged(java.util.Collection<org.opendaylight.mdsal.binding.api.DataTreeModification<T>>) would always be invoked for data changes.

Default implementation does nothing and is appropriate for users who do not care about ascertaining initial state.