How to edit a json file using jsoncons? - c++

Question

I am using jsoncons, which is a requirement for this question.
I am trying to edit some fields in a deeply nested json file, for example the following one:
{
"Error": null,
"HubNotificationId": "8a321f40-3692-11ec-b2a8-02420a0000fc",
"HubNotificationTimestamp": "2021-10-26T19:25:55.330812",
"MessageTimestampUtc": "2021-10-26T19:25:55",
"Result": "SUCCESS",
"ScanId": "0789e64f-87a7-42b0-a912-362acad7536c",
"ScanTimestampUtc": "2021-10-26T19:25:44",
"Source": {
"InstanceId": "",
"ModuleId": "atlas",
"ServiceId": "uv-acquisition-manager",
"ServiceVersion": "2.1.0-0001",
"SiteId": "rnd-oem-holon"
},
"Type": "ScanNotification",
"Version": "2.8.0",
"abortReason": null,
"context": "scan/end",
"data": [
{
"frameGrabberId": "at-uv-dm-fg1",
"scanLocation": {
"Original_ScaledDown": {
"keyPrefix": null,
"mimeType": "",
"role": "Original_ScaledDown",
"uri": "INJECTED"
},
"Undistorted_ScaledDown": {
"keyPrefix": null,
"mimeType": "",
"role": "Undistorted_ScaledDown",
"uri": "INJECTED"
},
"Unprocessed": {
"keyPrefix": "a0366334-b44b-459e-8484-8a0c835c6889/c5424457-9066-4d82-9ab9-df5cc2a17c21/20201006/2020-10-06T11-16-04.000Z_98021622-12ff-455b-972d-79af24c169a1",
"mimeType": "",
"role": "Unprocessed",
"uri": "INJECTED"
}
}
},
{
"frameGrabberId": "at-uv-dm-fg2",
"scanLocation": {
"Original_ScaledDown": {
"keyPrefix": null,
"mimeType": "",
"role": "Original_ScaledDown",
"uri": "INJECTED"
},
"Undistorted_ScaledDown": {
"keyPrefix": null,
"mimeType": "",
"role": "Undistorted_ScaledDown",
"uri": "INJECTED"
},
"Unprocessed": {
"keyPrefix": "INJECTED",
"mimeType": "",
"role": "Unprocessed",
"uri": "INJECTED"
}
}
},
{
"frameGrabberId": "at-uv-dm-fg3",
"scanLocation": {
"Original_ScaledDown": {
"keyPrefix": null,
"mimeType": "",
"role": "Original_ScaledDown",
"uri": "INJECTED"
},
"Undistorted_ScaledDown": {
"keyPrefix": null,
"mimeType": "",
"role": "Undistorted_ScaledDown",
"uri": "INJECTED"
},
"Unprocessed": {
"keyPrefix": "a0366334-b44b-459e-8484-8a0c835c6889/c5424457-9066-4d82-9ab9-df5cc2a17c21/20201006/2020-10-06T11-16-04.000Z_98021622-12ff-455b-972d-79af24c169a1",
"mimeType": "",
"role": "Unprocessed",
"uri": "INJECTED"
}
}
},
{
"frameGrabberId": "at-uv-dm-mgr",
"scanLocation": {
"Original_ScaledDown": {
"keyPrefix": null,
"mimeType": "",
"role": "Original_ScaledDown",
"uri": "INJECTED"
},
"Undistorted_ScaledDown": {
"keyPrefix": null,
"mimeType": "",
"role": "Undistorted_ScaledDown",
"uri": "INJECTED"
},
"Unprocessed": {
"keyPrefix": "a0366334-b44b-459e-8484-8a0c835c6889/c5424457-9066-4d82-9ab9-df5cc2a17c21/20201006/2020-10-06T11-16-04.000Z_98021622-12ff-455b-972d-79af24c169a1",
"mimeType": "",
"role": "Unprocessed",
"uri": "INJECTED"
}
}
}
],
"dynamicMetaData": {
"vehicleParams": {
"color": "122",
"model": "225",
"vendor": "a"
}
},
"scanDuration_sec": 10.98,
"shotsCount": 96,
"sourceInfo": [],
"staticMetaData": null
}
I want to edit some of the keys - for example, the uri keys.
How to use the library to be able to edit the json and save an edited copy?
What I have so far is
const jsoncons::json& TestMessage::injectPathToFMTemplate(const std::string &scanPath) {
auto& raw = this->_raw_input;
auto& parsed = this->_templateMessage;
auto parsedTree = parsed.as<std::map<std::string, jsoncons::json>>();
auto dataPos = parsedTree.find("data");
auto& data = dataPos->second;
auto grabbers = data.as<std::vector<std::map<std::string, jsoncons::json>>>();
int grabberIndex = 0;
for (auto& grabberTree : grabbers){
auto scanLocationPos = grabberTree.find("scanLocation");
auto scanLocationTree = scanLocationPos->second.as<std::map<std::string, jsoncons::json>>();
auto Original_ScaledDownPos = scanLocationTree.find("Original_ScaledDown");
auto Undistorted_ScaledDownPos = scanLocationTree.find("Undistorted_ScaledDown");
auto UnprocessedPos = scanLocationTree.find("Unprocessed");
auto Original_ScaledDownPosTree = Original_ScaledDownPos->second.as<std::map<std::string, jsoncons::json>>();
auto Undistorted_ScaledDownPosTree = Original_ScaledDownPos->second.as<std::map<std::string, jsoncons::json>>();
auto UnprocessedPosTree = Original_ScaledDownPos->second.as<std::map<std::string, jsoncons::json>>();
auto uriPos1 = Original_ScaledDownPosTree.find("uri");
auto uriPos2 = Undistorted_ScaledDownPosTree.find("uri");
auto uriPos3 = UnprocessedPosTree.find("uri");
uriPos1->second = scanPath;
uriPos2->second = scanPath;
uriPos3->second = scanPath;
++grabberIndex;
}
parsed = jsoncons::json(parsedTree);
auto s = parsed.as<std::string>();
return parsed;
Which goes all the way down to the uri fields, but then can't edit them because nothing is (or can be) by reference, and I find that I have to re-build all of the json object again, which makes no sense.
I am sure the library allows this somehow, just can't find out how.

Answer 1

The jsoncons library provides a number of options for editing a JSON value, but a simple way is
std::string scanPath = "FOO";
try
{
json root = json::parse(input);
json& data = root.at("data");
for (auto& grabberTree : data.array_range())
{
json& scanLocationTree = grabberTree.at("scanLocation");
json& Original_ScaledDown = scanLocationTree.at("Original_ScaledDown");
json& Undistorted_ScaledDown = scanLocationTree.at("Undistorted_ScaledDown");
json& Unprocessed = scanLocationTree.at("Unprocessed");
Original_ScaledDown.at("uri") = scanPath;
Undistorted_ScaledDown.at("uri") = scanPath;
Unprocessed.at("uri") = scanPath;
}
std::cout << pretty_print(root) << "\n";
}
catch (const std::exception& e)
{
std::cout << e.what() << "\n";
}