CPS-1401 Implement V2 of GET Data Node API

- Modified the GET Data Node API so it returns all the data nodes when
  xpath set to root "/"
- Fragment Repository now returns a collection of Fragment Entities
- Instead of returning only the first Fragment Entity now all fragment
  entities are returned when xpath is set to root
- The Fragemnt Entities are further processed to a Collection of Data
  Nodes. As opposed to singular Data Node in current implementation.
- Finally the DataRestController also returns a Collection of Data
  Nodes when xpath is set to root and valid data is present
- Response body changed from JSON object to JSON Array.
- Exception handling for invalid xpath and non-existing xpath is now
  done separately at persistence layer.
- Refactored code against CPS-1422
- Deprecated getDataNode method from Service and Persistence layer
- Modified V1 of Get Data Node API to use the getDataNodes method and
  get the first data node from the collection returned.
- Modified NCMP to use getDataNodes method
- NCMP still does not support multiple data nodes. It retrieves the
  first data node from the collection returned by getDataNodes

Signed-off-by: arpitsingh <as00745003@techmahindra.com>
Change-Id: I494a5740a53f65376d135fcb9f1e2e8900a2803e

4 files changed, 53 insertions, 45 deletions

diff --git a/cps-service/src/main/java/org/onap/cps/api/CpsDataService.java b/cps-service/src/main/java/org/onap/cps/api/CpsDataService.java
index 174d71f64..9f96df2e4 100644
--- a/cps-service/src/main/java/org/onap/cps/api/CpsDataService.java
+++ b/cps-service/src/main/java/org/onap/cps/api/CpsDataService.java
@@ -4,6 +4,7 @@
  *  Modifications Copyright (C) 2021 Pantheon.tech
  *  Modifications Copyright (C) 2021-2022 Bell Canada
  *  Modifications Copyright (C) 2022 Deutsche Telekom AG
+ *  Modifications Copyright (C) 2023 TechMahindra Ltd.
  *  ================================================================================
  *  Licensed under the Apache License, Version 2.0 (the "License");
  *  you may not use this file except in compliance with the License.
@@ -110,30 +111,31 @@ public interface CpsDataService {
             Collection<String> jsonDataList, OffsetDateTime observedTimestamp);
 
     /**
-     * Retrieves datanode by XPath for given dataspace and anchor.
+     * Retrieves all the datanodes by XPath for given dataspace and anchor.
      *
-     * @param dataspaceName          dataspace name
-     * @param anchorName             anchor name
-     * @param xpath                  xpath
-     * @param fetchDescendantsOption defines the scope of data to fetch: either single node or all the descendant nodes
-     *                               (recursively) as well
-     * @return data node object
+     * @param dataspaceName           dataspace name
+     * @param anchorName              anchor name
+     * @param xpath                   xpath
+     * @param fetchDescendantsOption  defines the scope of data to fetch: either single node or all the descendant nodes
+     *                                (recursively) as well
+     * @return collection of data node objects
      */
-    DataNode getDataNode(String dataspaceName, String anchorName, String xpath,
-        FetchDescendantsOption fetchDescendantsOption);
+    Collection<DataNode> getDataNodes(String dataspaceName, String anchorName, String xpath,
+                                      FetchDescendantsOption fetchDescendantsOption);
 
     /**
-     * Retrieves datanodes by XPath for given dataspace and anchor.
+     * Retrieves all the datanodes for multiple XPaths for given dataspace and anchor.
      *
-     * @param dataspaceName          dataspace name
-     * @param anchorName             anchor name
-     * @param xpaths                 collection of xpath
-     * @param fetchDescendantsOption defines the scope of data to fetch: either single node or all the descendant nodes
-     *                               (recursively) as well
-     * @return data node object
+     * @param dataspaceName           dataspace name
+     * @param anchorName              anchor name
+     * @param xpaths                  collection of xpaths
+     * @param fetchDescendantsOption  defines the scope of data to fetch: either single node or all the descendant nodes
+     *                                (recursively) as well
+     * @return collection of data node objects
      */
-    Collection<DataNode> getDataNodes(String dataspaceName, String anchorName, Collection<String> xpaths,
-                         FetchDescendantsOption fetchDescendantsOption);
+    Collection<DataNode> getDataNodesForMultipleXpaths(String dataspaceName, String anchorName,
+                                                       Collection<String> xpaths,
+                                                       FetchDescendantsOption fetchDescendantsOption);
 
     /**
      * Updates data node for given dataspace and anchor using xpath to parent node.
diff --git a/cps-service/src/main/java/org/onap/cps/api/impl/CpsDataServiceImpl.java b/cps-service/src/main/java/org/onap/cps/api/impl/CpsDataServiceImpl.java
index 06a084538..b149d426e 100755
--- a/cps-service/src/main/java/org/onap/cps/api/impl/CpsDataServiceImpl.java
+++ b/cps-service/src/main/java/org/onap/cps/api/impl/CpsDataServiceImpl.java
@@ -3,7 +3,7 @@
  *  Copyright (C) 2021-2023 Nordix Foundation
  *  Modifications Copyright (C) 2020-2022 Bell Canada.
  *  Modifications Copyright (C) 2021 Pantheon.tech
- *  Modifications Copyright (C) 2022 TechMahindra Ltd.
+ *  Modifications Copyright (C) 2022-2023 TechMahindra Ltd.
  *  Modifications Copyright (C) 2022 Deutsche Telekom AG
  *  ================================================================================
  *  Licensed under the Apache License, Version 2.0 (the "License");
@@ -134,21 +134,23 @@ public class CpsDataServiceImpl implements CpsDataService {
 
     @Override
     @Timed(value = "cps.data.service.datanode.get",
-        description = "Time taken to get a data node")
-    public DataNode getDataNode(final String dataspaceName, final String anchorName, final String xpath,
-        final FetchDescendantsOption fetchDescendantsOption) {
+            description = "Time taken to get data nodes for an xpath")
+    public Collection<DataNode> getDataNodes(final String dataspaceName, final String anchorName,
+                                             final String xpath,
+                                             final FetchDescendantsOption fetchDescendantsOption) {
         cpsValidator.validateNameCharacters(dataspaceName, anchorName);
-        return cpsDataPersistenceService.getDataNode(dataspaceName, anchorName, xpath, fetchDescendantsOption);
+        return cpsDataPersistenceService.getDataNodes(dataspaceName, anchorName, xpath, fetchDescendantsOption);
     }
 
     @Override
     @Timed(value = "cps.data.service.datanode.batch.get",
         description = "Time taken to get a batch of data nodes")
-    public Collection<DataNode> getDataNodes(final String dataspaceName, final String anchorName,
-                                             final Collection<String> xpaths,
-                                final FetchDescendantsOption fetchDescendantsOption) {
+    public Collection<DataNode> getDataNodesForMultipleXpaths(final String dataspaceName, final String anchorName,
+                                                              final Collection<String> xpaths,
+                                                              final FetchDescendantsOption fetchDescendantsOption) {
         cpsValidator.validateNameCharacters(dataspaceName, anchorName);
-        return cpsDataPersistenceService.getDataNodes(dataspaceName, anchorName, xpaths, fetchDescendantsOption);
+        return cpsDataPersistenceService.getDataNodesForMultipleXpaths(dataspaceName, anchorName, xpaths,
+                fetchDescendantsOption);
     }
 
     @Override
diff --git a/cps-service/src/main/java/org/onap/cps/notification/CpsDataUpdatedEventFactory.java b/cps-service/src/main/java/org/onap/cps/notification/CpsDataUpdatedEventFactory.java
index f0cdaee8d..38f898827 100644
--- a/cps-service/src/main/java/org/onap/cps/notification/CpsDataUpdatedEventFactory.java
+++ b/cps-service/src/main/java/org/onap/cps/notification/CpsDataUpdatedEventFactory.java
@@ -2,6 +2,7 @@
  * ============LICENSE_START=======================================================
  * Copyright (c) 2021-2022 Bell Canada.
  * Modifications Copyright (c) 2022 Nordix Foundation
+ * Modifications Copyright (C) 2023 TechMahindra Ltd.
  * ================================================================================
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -76,8 +77,8 @@ public class CpsDataUpdatedEventFactory {
     public CpsDataUpdatedEvent createCpsDataUpdatedEvent(final Anchor anchor,
         final OffsetDateTime observedTimestamp, final Operation operation) {
         final var dataNode = (operation == Operation.DELETE) ? null :
-            cpsDataService.getDataNode(anchor.getDataspaceName(), anchor.getName(),
-                "/", FetchDescendantsOption.INCLUDE_ALL_DESCENDANTS);
+            cpsDataService.getDataNodes(anchor.getDataspaceName(), anchor.getName(),
+                "/", FetchDescendantsOption.INCLUDE_ALL_DESCENDANTS).iterator().next();
         return toCpsDataUpdatedEvent(anchor, dataNode, observedTimestamp, operation);
     }
 
diff --git a/cps-service/src/main/java/org/onap/cps/spi/CpsDataPersistenceService.java b/cps-service/src/main/java/org/onap/cps/spi/CpsDataPersistenceService.java
index 3e0b4475e..0b2cef9bd 100644
--- a/cps-service/src/main/java/org/onap/cps/spi/CpsDataPersistenceService.java
+++ b/cps-service/src/main/java/org/onap/cps/spi/CpsDataPersistenceService.java
@@ -3,7 +3,7 @@
  *  Copyright (C) 2020-2023 Nordix Foundation.
  *  Modifications Copyright (C) 2021 Pantheon.tech
  *  Modifications Copyright (C) 2022 Bell Canada
- *  Modifications Copyright (C) 2022 TechMahindra Ltd.
+ *  Modifications Copyright (C) 2022-2023 TechMahindra Ltd.
  * ================================================================================
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -99,30 +99,33 @@ public interface CpsDataPersistenceService {
             Collection<Collection<DataNode>> newLists);
 
     /**
-     * Retrieves datanode by XPath for given dataspace and anchor.
+     * Retrieves multiple datanodes for a single XPath for given dataspace and anchor.
+     * Multiple data nodes are returned when xPath is set to root '/', otherwise single data node
+     * is returned when a specific xpath is used (Example: /bookstore).
      *
      * @param dataspaceName          dataspace name
      * @param anchorName             anchor name
-     * @param xpath                  xpath
+     * @param xpath                  one xpath
      * @param fetchDescendantsOption defines the scope of data to fetch: either single node or all the descendant nodes
      *                               (recursively) as well
-     * @return data node object
+     * @return collection of data node object
      */
-    DataNode getDataNode(String dataspaceName, String anchorName, String xpath,
-        FetchDescendantsOption fetchDescendantsOption);
+    Collection<DataNode> getDataNodes(String dataspaceName, String anchorName, String xpath,
+                                      FetchDescendantsOption fetchDescendantsOption);
 
     /**
-     * Retrieves datanode by XPath for given dataspace and anchor.
+     * Retrieves multiple datanodes for multiple XPaths, given a dataspace and anchor.
      *
-     * @param dataspaceName          dataspace name
-     * @param anchorName             anchor name
-     * @param xpaths                 collection of xpaths
-     * @param fetchDescendantsOption defines the scope of data to fetch: either single node or all the descendant nodes
-     *                               (recursively) as well
-     * @return data node object
-     */
-    Collection<DataNode> getDataNodes(String dataspaceName, String anchorName, Collection<String> xpaths,
-                         FetchDescendantsOption fetchDescendantsOption);
+     * @param dataspaceName           dataspace name
+     * @param anchorName              anchor name
+     * @param xpaths                  collection of xpaths
+     * @param fetchDescendantsOption  defines the scope of data to fetch: either single node or all the descendant nodes
+     *                                (recursively) as well
+     * @return collection of data node object
+     */
+    Collection<DataNode> getDataNodesForMultipleXpaths(String dataspaceName, String anchorName,
+                                                       Collection<String> xpaths,
+                                                       FetchDescendantsOption fetchDescendantsOption);
 
     /**
      * Updates leaves for existing data node.