Merge branch 'bug/json-body-non-object-types' into 'release'

Handle 500 when JSON body doesn't make up an object data type.

See merge request theappsmith/internal-tools-server!316

app/server/appsmith-plugins/restApiPlugin/src/main/java/com/external/plugins/RestApiPlugin.java

@@ -11,6 +11,7 @@ import com.appsmith.external.plugins.BasePlugin;
 import com.appsmith.external.plugins.PluginExecutor;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.google.gson.GsonBuilder;
+import com.google.gson.JsonSyntaxException;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.commons.lang.StringUtils;
 import org.bson.internal.Base64;
@@ -191,15 +192,23 @@ public class RestApiPlugin extends BasePlugin {
             if (iteration == MAX_REDIRECTS) {
                 return Mono.error(new AppsmithPluginException(
                         AppsmithPluginError.PLUGIN_ERROR,
-                        "Exceeded the HTTO redirect limits of " + MAX_REDIRECTS
+                        "Exceeded the HTTP redirect limits of " + MAX_REDIRECTS
                 ));
             }
 
-            Object requestBodyAsObject;
+            Object requestBodyAsObject = null;
             if (isJsonContentType) {
-                GsonBuilder gson = new GsonBuilder();
+                try {
-                requestBodyAsObject = gson.create().fromJson(requestBodyAsString, Map.class);
+                    requestBodyAsObject = objectFromJson(requestBodyAsString);
-            } else {
+                } catch (JsonSyntaxException e) {
+                    return Mono.error(new AppsmithPluginException(
+                            AppsmithPluginError.PLUGIN_ERROR,
+                            "Malformed JSON: " + e.getMessage()
+                    ));
+                }
+            }
+
+            if (requestBodyAsObject == null) {
                 requestBodyAsObject = requestBodyAsString;
             }
 
@@ -232,6 +241,31 @@ public class RestApiPlugin extends BasePlugin {
                     });
         }
 
+        /**
+         * Given a JSON string, we infer the top-level type of the object it represents and then parse it into that
+         * type. However, only `Map` and `List` top-levels are supported. Note that the map or list may contain
+         * anything, like booleans or number or even more maps or lists. It's only that the top-level type should be a
+         * map / list.
+         * @param jsonString A string that confirms to JSON syntax. Shouldn't be null.
+         * @return An object of type `Map`, `List`, if applicable, or `null`.
+         */
+        private static Object objectFromJson(String jsonString) {
+            Class<?> type;
+            String trimmed = jsonString.trim();
+
+            if (trimmed.startsWith("{")) {
+                type = Map.class;
+            } else if (trimmed.startsWith("[")) {
+                type = List.class;
+            } else {
+                // The JSON body is likely a literal boolean or number or string. For our purposes here, we don't have
+                // to parse this JSON.
+                return null;
+            }
+
+            return new GsonBuilder().create().fromJson(jsonString, type);
+        }
+
         @Override
         public Mono<Object> datasourceCreate(DatasourceConfiguration datasourceConfiguration) {
             return Mono.empty();