Multiview request changes to support Couch3

POST directly to the view was deprecated in CouchDB 2.2 and is now removed in Couch3.
Try POST to /queries first and if that fails, fallback to POST to the view.

Author: ricellis

CHANGES.md

@@ -1,5 +1,7 @@
 # Unreleased
 - [NEW] Add getter for total row count to AllDocsResponse
+- [FIXED] `ViewMultipleRequest` updated to preferentially use view `queries` format URL instead of
+  deprecated format.
 
 # 2.18.0 (2019-10-02)
 - [FIXED] Create an array of strings for QueryBuilder.fields() when a single field is provided.

cloudant-client/src/main/java/com/cloudant/client/internal/views/ViewMultipleRequester.java

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2015, 2018 IBM Corp. All rights reserved.
+ * Copyright © 2015, 2020 IBM Corp. All rights reserved.
  *
  * 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
@@ -16,12 +16,15 @@
 
 import com.cloudant.client.api.views.ViewMultipleRequest;
 import com.cloudant.client.api.views.ViewResponse;
+import com.cloudant.client.org.lightcouch.CouchDbException;
 import com.cloudant.http.Http;
 import com.cloudant.http.HttpConnection;
 import com.google.gson.JsonArray;
 import com.google.gson.JsonObject;
 
 import java.io.IOException;
+import java.net.HttpURLConnection;
+import java.net.URI;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
@@ -43,12 +46,22 @@ public List<ViewResponse<K, V>> getViewResponses() throws IOException {
         }
         JsonObject queryJson = new JsonObject();
         queryJson.add("queries", queries);
+        String requestBody = queryJson.toString();
         //construct and execute the POST request
-        HttpConnection post = Http.POST(viewQueryParameters.getViewURIBuilder().build(),
-                "application/json");
-        post.setRequestBody(queryJson.toString());
-        JsonObject jsonResponse = ViewRequester.executeRequestWithResponseAsJson
-                (viewQueryParameters, post);
+        URI multiRequestUri = viewQueryParameters.getViewURIBuilder().path("queries").build();
+        JsonObject jsonResponse = null;
+        try {
+            jsonResponse = performMultiRequest(multiRequestUri, viewQueryParameters, requestBody);
+        } catch (CouchDbException e) {
+            if (e.getStatusCode() == HttpURLConnection.HTTP_INTERNAL_ERROR && "badmatch".equals(e.getError())) {
+                // CouchDB versions prior to 2.2 don't support .../_view/{viewname}/queries
+                // POST directly to view instead
+                multiRequestUri = viewQueryParameters.getViewURIBuilder().build();
+                jsonResponse = performMultiRequest(multiRequestUri, viewQueryParameters, requestBody);
+            } else {
+                throw e;
+            }
+        }
         //loop the returned array creating the ViewResponse objects
         List<ViewResponse<K, V>> responses = new ArrayList<ViewResponse<K, V>>();
         JsonArray jsonResponses = jsonResponse.getAsJsonArray("results");
@@ -68,4 +81,13 @@ public List<ViewResponse<K, V>> getViewResponses() throws IOException {
     public void add(ViewQueryParameters<K, V> viewQueryParameters) {
         requestParameters.add(viewQueryParameters);
     }
+
+    private JsonObject performMultiRequest(URI multiRequestUri,
+                                           ViewQueryParameters<K, V> viewQueryParameters,
+                                           String body) throws CouchDbException, IOException {
+        //construct and execute the POST request
+        HttpConnection post = Http.POST(multiRequestUri, "application/json");
+        post.setRequestBody(body);
+        return ViewRequester.executeRequestWithResponseAsJson(viewQueryParameters, post);
+    }
 }