Fix onDataTreeChanged() references

[mdsal.git] / dom / mdsal-dom-api / src / main / java / org / opendaylight / mdsal / dom / api / DOMDataTreeChangeListener.java

diff --git a/dom/mdsal-dom-api/src/main/java/org/opendaylight/mdsal/dom/api/DOMDataTreeChangeListener.java b/dom/mdsal-dom-api/src/main/java/org/opendaylight/mdsal/dom/api/DOMDataTreeChangeListener.java
index 2ae4f780dbb322495302c18321193dce865ea62b..0c0aeb23e6a07277d5bd67458978396142d7e526 100644 (file)
--- a/dom/mdsal-dom-api/src/main/java/org/opendaylight/mdsal/dom/api/DOMDataTreeChangeListener.java
+++ b/dom/mdsal-dom-api/src/main/java/org/opendaylight/mdsal/dom/api/DOMDataTreeChangeListener.java
@@ -25,6 +25,9 @@ public interface DOMDataTreeChangeListener extends EventListener {
      * in the conceptual data tree for supplied path. This initial event will contain all pre-existing data as created.
      *
      * <p>
+     * Note: If there is no pre-existing data, the method {@link #onInitialData} will be invoked.
+     *
+     * <p>
      * 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
@@ -36,4 +39,17 @@ public interface DOMDataTreeChangeListener extends EventListener {
      * @throws NullPointerException if {@code changes} is null
      */
     void onDataTreeChanged(@NonNull Collection<DataTreeCandidate> changes);
+
+    /**
+     * 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
+     * {@link #onDataTreeChanged(Collection)} would always be invoked for data changes.
+     *
+     * <p>
+     * Default implementation does nothing and is appropriate for users who do not care about ascertaining
+     * initial stat.
+     */
+    default void onInitialData() {
+        //no-op
+    }
 }