Implemented get-data

- RFC-8526: https://datatracker.ietf.org/doc/html/rfc8526#section-3.1.1
- Also, updated filter variable name to be specific to xpathfilter
- Per PR discussion, using Locale.US isntead of Locale.ROOT to be more
  specific to US letters, as the RFC is in US english.

Author: senderic

src/main/java/net/juniper/netconf/Device.java

@@ -31,6 +31,7 @@
 import java.nio.charset.Charset;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Locale;
 
 /**
  * A <code>Device</code> is used to define a Netconf server.
@@ -838,14 +839,48 @@ public XML getRunningConfig(String configTree) throws SAXException,
         return this.netconfSession.getRunningConfig(configTree);
     }
 
-    public XML getRunningConfigAndState(String filter) throws IOException, SAXException {
+    /**
+     * Retrieve the running configuration, or part of the configuration.
+     *
+     * @param xpathFilter example <code><filter xmlns:model='urn:path:for:my:model' select='/model:*'></filter></code>
+     * @return configuration data as XML object.
+     * @throws java.io.IOException      If there are errors communicating with the netconf server.
+     * @throws org.xml.sax.SAXException If there are errors parsing the XML reply.
+     */
+    public XML getRunningConfigAndState(String xpathFilter) throws IOException, SAXException {
+        if (netconfSession == null) {
+            throw new IllegalStateException("Cannot execute RPC, you need to " +
+                    "establish a connection first.");
+        }
+        return this.netconfSession.getRunningConfigAndState(xpathFilter);
+    }
+
+
+    /**
+     * Run the <get-data> call to netconf server and retrieve data as an XML.
+     *
+     * @param xpathFilter example <code><filter xmlns:model='urn:path:for:my:model' select='/model:*'></filter></code>
+     * @param datastore running, startup, candidate, or operational
+     * @return configuration data as XML object.
+     * @throws java.io.IOException      If there are errors communicating with the netconf server.
+     * @throws org.xml.sax.SAXException If there are errors parsing the XML reply.
+     */
+    public XML getData(String xpathFilter, String datastore) throws IOException, SAXException {
         if (netconfSession == null) {
             throw new IllegalStateException("Cannot execute RPC, you need to " +
                     "establish a connection first.");
         }
-        return this.netconfSession.getRunningConfigAndState(filter);
+        if (datastore != null) switch (datastore.trim().toLowerCase(Locale.US)) {
+            case "running":
+            case "startup":
+            case "candidate":
+            case "operational":
+                return this.netconfSession.getData(xpathFilter, datastore.trim().toLowerCase(Locale.US));
+        }
+        throw new IllegalStateException("Unable to process datastore: " + datastore);
     }
 
+
     /**
      * Retrieve the whole candidate configuration.
      *

src/main/java/net/juniper/netconf/NetconfSession.java

@@ -159,6 +159,8 @@ private void sendRpcRequest(String rpc) throws IOException {
         // RFC conformance for XML type, namespaces and message ids for RPCs
         messageId++;
         rpc = rpc.replace("<rpc>", "<rpc" + getRpcAttributes() + " message-id=\"" + messageId + "\">").trim();
+        rpc = rpc.replace("<datastore>", "<datastore xmlns:ds=\"urn:ietf:params:xml:ns:yang:ietf-datastores\">");
+        rpc = rpc.replace("<get-data>", "<get-data xmlns=\"urn:ietf:params:xml:ns:yang:ietf-netconf-nmda\">");
         if (!rpc.contains(NetconfConstants.XML_VERSION)) {
             rpc = NetconfConstants.XML_VERSION + rpc;
         }
@@ -301,17 +303,31 @@ private String getConfig(String configTree) throws IOException {
         return lastRpcReply;
     }
 
-    public XML getRunningConfigAndState(String filter) throws IOException, SAXException {
+    public XML getRunningConfigAndState(String xpathFilter) throws IOException, SAXException {
         String rpc = "<rpc>" +
                 "<get>" +
-                (filter == null ? "" : filter) +
+                (xpathFilter == null ? "" : xpathFilter) +
                 "</get>" +
                 "</rpc>" +
                 NetconfConstants.DEVICE_PROMPT;
         setLastRpcReply(getRpcReply(rpc));
         return convertToXML(lastRpcReply);
     }
 
+    public XML getData(String xpathFilter, String datastore)
+            throws IOException, SAXException {
+
+        String rpc = "<rpc>" +
+                "<get-data>" +
+                "<datastore>ds:" + datastore + "</datastore>" +
+                (xpathFilter == null ? "" : xpathFilter) +
+                "</get-data>" +
+                "</rpc>" +
+                NetconfConstants.DEVICE_PROMPT;
+        lastRpcReply = getRpcReply(rpc);
+        return convertToXML(lastRpcReply);
+    }
+
     private String getConfig(String target, String configTree)
             throws IOException {