[enhancement]: Jsoncpp cannot read content in order

[Cavey-QW]

[GuoYongFa]

nlohmann/json might be a good alternative, with examples as follows：

#include <iostream>
#include <nlohmann/json.hpp>
#include <sstream>

// For simplicity, use the namespace provided by the library
using ordered_json = nlohmann::ordered_json;

int main() {
  // Example JSON string
  std::string jsonString = R"({
        "execution": {
            "b_step": {},
            "a_step": {},
            "c_step": {}
        }
    })";

  // Use a stringstream to read the JSON string
  std::stringstream jsonStream(jsonString);
  ordered_json j;
  jsonStream >> j;

  // Ensure the "execution" node exists
  if (j.contains("execution")) {
    // Get all child nodes under "execution" and output them in order
    ordered_json execution_node = j["execution"];
    for (auto it = execution_node.begin(); it != execution_node.end(); ++it) {
      std::cout << it.key() << ": " << it.value() << std::endl;
    }
  } else {
    std::cout << "No 'execution' node found." << std::endl;
  }

  return 0;
}

The CMakeLists.txt is as follows：

find_package(nlohmann_json REQUIRED)
add_executable(${PROJECT_NAME} main.cpp)
target_link_libraries(${PROJECT_NAME} PRIVATE  nlohmann_json::nlohmann_json)