Add ser/deser to get AD transport action request (#1150) (#1151)

Signed-off-by: Tyler Ohlsen <ohltyler@amazon.com>

Author: ohltyler

src/main/java/org/opensearch/ad/transport/GetAnomalyDetectorRequest.java

@@ -11,11 +11,15 @@
 
 package org.opensearch.ad.transport;
 
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 
 import org.opensearch.action.ActionRequest;
 import org.opensearch.action.ActionRequestValidationException;
 import org.opensearch.ad.model.Entity;
+import org.opensearch.core.common.io.stream.InputStreamStreamInput;
+import org.opensearch.core.common.io.stream.OutputStreamStreamOutput;
 import org.opensearch.core.common.io.stream.StreamInput;
 import org.opensearch.core.common.io.stream.StreamOutput;
 
@@ -119,4 +123,19 @@ public void writeTo(StreamOutput out) throws IOException {
     public ActionRequestValidationException validate() {
         return null;
     }
+
+    public static GetAnomalyDetectorRequest fromActionRequest(final ActionRequest actionRequest) {
+        if (actionRequest instanceof GetAnomalyDetectorRequest) {
+            return (GetAnomalyDetectorRequest) actionRequest;
+        }
+
+        try (ByteArrayOutputStream baos = new ByteArrayOutputStream(); OutputStreamStreamOutput osso = new OutputStreamStreamOutput(baos)) {
+            actionRequest.writeTo(osso);
+            try (StreamInput input = new InputStreamStreamInput(new ByteArrayInputStream(baos.toByteArray()))) {
+                return new GetAnomalyDetectorRequest(input);
+            }
+        } catch (IOException e) {
+            throw new IllegalArgumentException("failed to parse ActionRequest into GetAnomalyDetectorRequest", e);
+        }
+    }
 }

src/main/java/org/opensearch/ad/transport/GetAnomalyDetectorTransportAction.java

@@ -37,6 +37,7 @@
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.opensearch.OpenSearchStatusException;
+import org.opensearch.action.ActionRequest;
 import org.opensearch.action.get.MultiGetItemResponse;
 import org.opensearch.action.get.MultiGetRequest;
 import org.opensearch.action.get.MultiGetResponse;
@@ -75,7 +76,7 @@
 
 import com.google.common.collect.Sets;
 
-public class GetAnomalyDetectorTransportAction extends HandledTransportAction<GetAnomalyDetectorRequest, GetAnomalyDetectorResponse> {
+public class GetAnomalyDetectorTransportAction extends HandledTransportAction<ActionRequest, GetAnomalyDetectorResponse> {
 
     private static final Logger LOG = LogManager.getLogger(GetAnomalyDetectorTransportAction.class);
 
@@ -131,7 +132,9 @@ public GetAnomalyDetectorTransportAction(
     }
 
     @Override
-    protected void doExecute(Task task, GetAnomalyDetectorRequest request, ActionListener<GetAnomalyDetectorResponse> actionListener) {
+    protected void doExecute(Task task, ActionRequest actionRequest, ActionListener<GetAnomalyDetectorResponse> actionListener) {
+        GetAnomalyDetectorRequest request = GetAnomalyDetectorRequest.fromActionRequest(actionRequest);
+
         String detectorID = request.getDetectorID();
         User user = getUserContext(client);
         ActionListener<GetAnomalyDetectorResponse> listener = wrapRestActionListener(actionListener, FAIL_TO_GET_DETECTOR);