[ONOS-4694] YANG management system outline and YMSM/YDT interfaces
Change-Id: I050ed98ba18edc2c2cea2abafeee6d8c9061b579
diff --git a/apps/yms/api/src/main/java/org/onosproject/yms/ydt/YdtListener.java b/apps/yms/api/src/main/java/org/onosproject/yms/ydt/YdtListener.java
new file mode 100644
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+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yms.ydt;
+
+/**
+ * Abstraction of an entity which provide call back methods which are called
+ * by YDT walker while walking the YANG data tree.
+ *
+ * In a response to execute operation YMS returns the YMS operation results
+ * with root YDT node. Now, protocols needs to walk through the YDT node and
+ * constructs the corresponding data format string. Protocol can opt to use
+ * listener or visitor based walking mechanism.
+ *
+ * This interface needs to be implemented by protocol implementing listener's
+ * based call backs while YDT walk.
+ */
+public interface YdtListener {
+
+ /**
+ * YANG data tree node's entry, it will be called during a node entry.
+ * All the related information about the node can be obtain from the YDT
+ * context.
+ *
+ * @param ydtContext YANG data tree context
+ */
+ void enterYdtNode(YdtContext ydtContext);
+
+ /**
+ * YANG data tree node's exit, it will be called during a node exit.
+ * All the related information about the node can be obtain from the YDT
+ * context.
+ *
+ * @param ydtContext YANG data tree context
+ */
+ void exitYdtNode(YdtContext ydtContext);
+}