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, created a Datastore enum. Overriding toString in
  enum to ensure lowercase.

Author: senderic

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

@@ -17,6 +17,7 @@
 import lombok.NonNull;
 import lombok.ToString;
 import lombok.extern.slf4j.Slf4j;
+import net.juniper.netconf.element.Datastore;
 import net.juniper.netconf.element.Hello;
 import org.w3c.dom.Document;
 import org.xml.sax.SAXException;
@@ -838,14 +839,41 @@ 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(filter);
+        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, @NonNull Datastore datastore) throws IOException, SAXException {
+        if (netconfSession == null) {
+            throw new IllegalStateException("Cannot execute RPC, you need to " +
+                    "establish a connection first.");
+        }
+       return this.netconfSession.getData(xpathFilter, datastore);
+    }
+
+
     /**
      * Retrieve the whole candidate configuration.
      *

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

@@ -14,6 +14,7 @@
 import com.jcraft.jsch.JSchException;
 import lombok.NonNull;
 import lombok.extern.slf4j.Slf4j;
+import net.juniper.netconf.element.Datastore;
 import net.juniper.netconf.element.Hello;
 import net.juniper.netconf.element.RpcReply;
 import org.w3c.dom.Document;
@@ -159,6 +160,8 @@ 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 +304,31 @@ 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, @NonNull Datastore 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 {
 

src/main/java/net/juniper/netconf/element/Datastore.java

@@ -0,0 +1,18 @@
+package net.juniper.netconf.element;
+
+import java.util.Locale;
+
+/**
+ * Datastore
+ * <p>
+ * As defined by RFC-8342.
+ * See https://datatracker.ietf.org/doc/html/rfc8342#section-5
+ */
+public enum Datastore {
+    RUNNING, CANDIDATE, STARTUP, INTENDED, OPERATIONAL;
+
+    @Override
+    public String toString() {
+        return this.name().toLowerCase(Locale.US);
+    }
+}

src/test/java/net/juniper/netconf/DatastoreTest.java

@@ -0,0 +1,18 @@
+package net.juniper.netconf;
+
+import net.juniper.netconf.element.Datastore;
+import org.junit.Test;
+
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertThat;
+
+public class DatastoreTest {
+    @Test
+    public void testDatastoreName() {
+        assertThat(Datastore.OPERATIONAL.toString(), is("operational"));
+        assertThat(Datastore.RUNNING.toString(), is("running"));
+        assertThat(Datastore.CANDIDATE.toString(), is("candidate"));
+        assertThat(Datastore.STARTUP.toString(), is("startup"));
+        assertThat(Datastore.INTENDED.toString(), is("intended"));
+    }
+}