Expose a List of changes in DOMDataTreeChangeListener

[mdsal.git] / binding / mdsal-binding-api / src / main / java / org / opendaylight / mdsal / binding / api / DataTreeChangeListener.java

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 2dc28988a10b055a3bb61399fbd6c43505621b35..c9d4a351be1ab0ef119b00e530823638bf2cf11c 100644 (file)
--- 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
@@ -7,38 +7,50 @@
  */
 package org.opendaylight.mdsal.binding.api;
 
-import java.util.Collection;
-import java.util.EventListener;
-import javax.annotation.Nonnull;
+import java.util.List;
+import org.eclipse.jdt.annotation.NonNull;
 import org.opendaylight.yangtools.yang.binding.DataObject;
 
 /**
- * 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.
+ * Interface implemented by classes interested in receiving notifications about changes to a data tree. It provides
+ * a cursor-based view of the change, which has potentially lower overhead and allow more flexible consumption of change
+ * events.
  */
-public interface DataTreeChangeListener<T extends DataObject> extends EventListener {
+public interface DataTreeChangeListener<T extends DataObject> {
     /**
-     * Invoked when there was data change for the supplied path, which was used
-     * to register this listener.
+     * Invoked when there was data change for the supplied path, which was used to register this listener.
      *
      * <p>
-     * 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.
+     * 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.
      *
      * <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.
+     * 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.
      *
      *<p>
-     * In other words, it is completely acceptable to observe
-     * a {@link DataObjectModification}, while the state observed before and
-     * after- data items compare as equal.
+     * In other words, it is completely acceptable to observe a {@link DataObjectModification}, while the state observed
+     * before and after- data items compare as equal.
      *
-     * @param changes Collection of change events, may not be null or empty.
+     * @param changes List of change events, may not be null or empty.
+     */
+    void onDataTreeChanged(@NonNull List<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(List)} 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.
      */
-    void onDataTreeChanged(@Nonnull Collection<DataTreeModification<T>> changes);
+    // FIXME: 14.0.0: this method should be non-default
+    default void onInitialData() {
+        //no-op
+    }
 }