X-Git-Url: https://git.opendaylight.org/gerrit/gitweb?a=blobdiff_plain;f=binding%2Fmdsal-binding-api%2Fsrc%2Fmain%2Fjava%2Forg%2Fopendaylight%2Fmdsal%2Fbinding%2Fapi%2FDataTreeChangeListener.java;h=95f9c03afd2e293b56303e0ad0a3c51d51ed3cf4;hb=f23c00c51d7874475c91a9290b561a9ab1d0cdc5;hp=2dc28988a10b055a3bb61399fbd6c43505621b35;hpb=c241dcfa5322ac10810a1068ccd2eb57f6f2dbb2;p=mdsal.git

diff --git a/binding/mdsal-binding-api/src/main/java/org/opendaylight/mdsal/binding/api/DataTreeChangeListener.java b/binding/mdsal-binding-api/src/main/java/org/opendaylight/mdsal/binding/api/DataTreeChangeListener.java
index 2dc28988a1..95f9c03afd 100644
--- a/binding/mdsal-binding-api/src/main/java/org/opendaylight/mdsal/binding/api/DataTreeChangeListener.java
+++ b/binding/mdsal-binding-api/src/main/java/org/opendaylight/mdsal/binding/api/DataTreeChangeListener.java
@@ -9,7 +9,7 @@ package org.opendaylight.mdsal.binding.api;
 
 import java.util.Collection;
 import java.util.EventListener;
-import javax.annotation.Nonnull;
+import org.eclipse.jdt.annotation.NonNull;
 import org.opendaylight.yangtools.yang.binding.DataObject;
 
 /**
@@ -28,6 +28,9 @@ public interface DataTreeChangeListener<T extends DataObject> extends EventListe
      * 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
@@ -40,5 +43,18 @@ public interface DataTreeChangeListener<T extends DataObject> extends EventListe
      *
      * @param changes Collection of change events, may not be null or empty.
      */
-    void onDataTreeChanged(@Nonnull Collection<DataTreeModification<T>> changes);
+    void onDataTreeChanged(@NonNull Collection<DataTreeModification<T>> 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 state.
+     */
+    default void onInitialData() {
+        //no-op
+    }
 }