MINIFICPP-1448 - Restructure and add comments

extensions/windows-event-log/ConsumeWindowsEventLog.cpp

@@ -34,7 +34,7 @@
 #include "wel/MetadataWalker.h"
 #include "wel/XMLString.h"
 #include "wel/UnicodeConversion.h"
-#include "wel/JSONConverter.h"
+#include "wel/JSONUtils.h"
 
 #include "io/BufferStream.h"
 #include "core/ProcessContext.h"
@@ -636,15 +636,15 @@ bool ConsumeWindowsEventLog::createEventRender(EVT_HANDLE hEvent, EventRender& e
   if (output_.json.simple) {
     logger_->log_trace("Writing event in simple JSON");
 
-    eventRender.json.simple = wel::jsonToString(wel::toJSON(doc, false));
+    eventRender.json.simple = wel::jsonToString(wel::toSimpleJSON(doc));
 
     logger_->log_trace("Finish writing in simple JSON");
   }
 
   if (output_.json.flattened) {
     logger_->log_trace("Writing event in flattened JSON");
 
-    eventRender.json.flattened = wel::jsonToString(wel::toJSON(doc, true));
+    eventRender.json.flattened = wel::jsonToString(wel::toFlattenedJSON(doc));
 
     logger_->log_trace("Finish writing in flattened JSON");
   }

extensions/windows-event-log/wel/JSONConverter.h → extensions/windows-event-log/wel/JSONUtils.cpp

@@ -15,10 +15,7 @@
  * limitations under the License.
  */
 
-#pragma once
-
-#undef RAPIDJSON_ASSERT
-#define RAPIDJSON_ASSERT(x) if (!(x)) throw std::logic_error("rapidjson exception");  // NOLINT
+#include "JSONUtils.h"
 
 #include <vector>
 #include <string>
@@ -39,7 +36,7 @@ namespace nifi {
 namespace minifi {
 namespace wel {
 
-rapidjson::Value xmlElementToJSON(const pugi::xml_node& node, rapidjson::Document& doc) {
+static rapidjson::Value xmlElementToJSON(const pugi::xml_node& node, rapidjson::Document& doc) {
   gsl_Expects(node.type() == pugi::xml_node_type::node_element);
   rapidjson::Value object(rapidjson::kObjectType);
   object.AddMember("name", rapidjson::StringRef(node.name()), doc.GetAllocator());
@@ -57,7 +54,7 @@ rapidjson::Value xmlElementToJSON(const pugi::xml_node& node, rapidjson::Documen
   return object;
 }
 
-rapidjson::Value xmlDocumentToJSON(const pugi::xml_node& node, rapidjson::Document& doc) {
+static rapidjson::Value xmlDocumentToJSON(const pugi::xml_node& node, rapidjson::Document& doc) {
   gsl_Expects(node.type() == pugi::xml_node_type::node_document);
   rapidjson::Value children(rapidjson::kArrayType);
   for (const auto& child : node.children()) {
@@ -76,7 +73,7 @@ rapidjson::Document toRawJSON(const pugi::xml_node& root) {
   return doc;
 }
 
-rapidjson::Document toJSON(const pugi::xml_node& root, bool flatten) {
+static rapidjson::Document toJSONImpl(const pugi::xml_node& root, bool flatten) {
   rapidjson::Document doc{rapidjson::kObjectType};
 
   auto event_xml = root.child("Event");
@@ -147,6 +144,14 @@ rapidjson::Document toJSON(const pugi::xml_node& root, bool flatten) {
   return doc;
 }
 
+rapidjson::Document toSimpleJSON(const pugi::xml_node& root) {
+  return toJSONImpl(root, false);
+}
+
+rapidjson::Document toFlattenedJSON(const pugi::xml_node& root) {
+  return toJSONImpl(root, true);
+}
+
 std::string jsonToString(rapidjson::Document& doc) {
   rapidjson::StringBuffer buffer;
   rapidjson::PrettyWriter<rapidjson::StringBuffer> writer(buffer);

extensions/windows-event-log/wel/JSONUtils.h

@@ -0,0 +1,70 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#undef RAPIDJSON_ASSERT
+#define RAPIDJSON_ASSERT(x) if (!(x)) throw std::logic_error("rapidjson exception");  // NOLINT
+
+#include <pugixml.hpp>
+
+#include "rapidjson/document.h"
+
+namespace org {
+namespace apache {
+namespace nifi {
+namespace minifi {
+namespace wel {
+
+/**
+ * Converts each xml element node to a json object of
+ * the form {name: String, attributes: Object, children: Array, text: String}
+ * Aims to preserve most of the input xml structure.
+ */
+rapidjson::Document toRawJSON(const pugi::xml_node& root);
+
+/**
+ * Retains some hierarchical structure of the original xml event,
+ * e.g. {System: {Provider: {Name: String, Guid: String}}}
+ */
+rapidjson::Document toSimpleJSON(const pugi::xml_node& root);
+
+/**
+ * Flattens most of the structure, i.e. removes intermediate
+ * objects and lifts innermost string-valued keys to the root.
+ * e.g. {System: {Provider: {Name: String}}} => {Name: String}
+ * 
+ * Moreover it also flattens each named data element where the
+ * name does not conflict with already existing members 
+ * (e.g. a data with name "Guid" won't be flattened as it would
+ * overwrite the existing "Guid" field).
+ * 
+ * e.g. {EventData: [{Name: "Test", Content: "X"}]} => {Test: "X"}
+ * 
+ * In order to mitigate data loss, it preserves the EventData
+ * array in its entirety as well.
+ * (otherwise a "Guid" data would be lost)
+ */
+rapidjson::Document toFlattenedJSON(const pugi::xml_node& root);
+
+std::string jsonToString(rapidjson::Document& doc);
+
+}  // namespace wel
+}  // namespace minifi
+}  // namespace nifi
+}  // namespace apache
+}  // namespace org