Method to extract ConfigurableParam as JSON string

Author: shahor02

Common/Utils/include/CommonUtils/ConfigurableParam.h

@@ -407,6 +407,8 @@ class ConfigurableParam
   // writes a human readable INI or JSON file depending on the extension
   static void write(std::string const& filename, std::string const& keyOnly = "");
 
+  static std::string asJSON(std::string const& keyOnly = "");
+
   // can be used instead of using API on concrete child classes
   template <typename T>
   static T getValueAs(std::string key)

Common/Utils/src/ConfigurableParam.cxx

@@ -754,6 +754,29 @@ void ConfigurableParam::writeJSON(std::string const& filename, std::string const
 
 // ------------------------------------------------------------------
 
+std::string ConfigurableParam::asJSON(std::string const& keyOnly)
+{
+  initPropertyTree(); // update the boost tree before writing
+  std::ostringstream os;
+  if (!keyOnly.empty()) { // write ini for selected key only
+    try {
+      boost::property_tree::ptree kTree;
+      auto keys = o2::utils::Str::tokenize(keyOnly, " ,;", true, true);
+      for (const auto& k : keys) {
+        kTree.add_child(k, sPtree->get_child(k));
+      }
+      boost::property_tree::write_json(os, kTree);
+    } catch (const boost::property_tree::ptree_bad_path& err) {
+      LOG(fatal) << "non-existing key " << keyOnly << " provided to writeJSON";
+    }
+  } else {
+    boost::property_tree::write_json(os, *sPtree);
+  }
+  return os.str();
+}
+
+// ------------------------------------------------------------------
+
 void ConfigurableParam::initPropertyTree()
 {
   sPtree->clear();