Trying to integrate rapidjson into my app. Used to read a (validated with an online tool) simple config file like:
{
"filecontent": "appsettings",
"fileversion": 1,
"appsettings": {
"general": {
"sync": "false",
"sound": "true"
},
...
This is my code:
QString path = keypath( key ); //.prepend("/");
rapidjson::Value* hello = rapidjson::Pointer( "/appsettings/general/sound" ) //path.toStdString().c_str()
.Get(rapidJsonDoc_);
if ( hello ) {
QVariant retStr( hello->GetString() );
qDebug()<<"--> " <<path<<" --> " << retStr;
ret = QVariant::fromValue( retStr );
}else{
qDebug()<<"Value not found!";
}
return ret;
If I prepend the pointer string with /, as I understand the examples, it says value not found.
If I remove the slash, if (hello) is true, but does not return an expected value.
rapidJsonDoc_ is of type rapidjson::Document.
Please help me with the correct syntax. I am looking at the source code of rapidjson and can't understand a thing, it is so full of templates and complex signatures...
update:
according to this post modifying a Qt QJsonDocument is not possible like I want.
Related
I know how to create a complete dom from an xml file just using XercesDOMParser:
xercesc::XercesDOMParser parser = new xercesc::XercesDOMParser();
parser->parse(path_to_my_file);
parser->getDocument(); // From here on I can access all nodes and do whatever i want
Well, that works... but what if I'd want to parse a string? Something like
std::string myxml = "<root>...</root>";
xercesc::XercesDOMParser parser = new xercesc::XercesDOMParser();
parser->parse(myxml);
parser->getDocument(); // From here on I can access all nodes and do whatever i want
I'm using version 3. Looking inside the AbstractDOMParser I see that parse method and its overloaded versions, only parse files.
How can I parse from a string?
Create a MemBufInputSource and parse that:
xercesc::MemBufInputSource myxml_buf(myxml.c_str(), myxml.size(),
"myxml (in memory)");
parser->parse(myxml_buf);
Use the following overload of XercesDOMParser::parse():
void XercesDOMParser::parse(const InputSource& source);
passing it a MemBufInputSource:
MemBufInputSource src((const XMLByte*)myxml.c_str(), myxml.length(), "dummy", false);
parser->parse(src);
Im doing it another way. If this is incorrect, please tell me why. It seems to work.
This is what parse expects:
DOMDocument* DOMLSParser::parse(const DOMLSInput * source )
So you need to put in a DOMLSInput instead of a an InputSource:
xercesc::DOMImplementation * impl = xercesc::DOMImplementation::getImplementation();
xercesc::DOMLSParser *parser = (xercesc::DOMImplementationLS*)impl)->createLSParser(xercesc::DOMImplementation::MODE_SYNCHRONOUS, 0);
xercesc::DOMDocument *doc;
xercesc::Wrapper4InputSource source (new xercesc::MemBufInputSource((const XMLByte *) (myxml.c_str()), myxml.size(), "A name");
parser->parse(&source);
You may use MemBufInputSource as found in the xercesc/framework/MemBufInputSource.cpp, and the header file, MemBufInputSource.hpp contains extensive documentation, as similar to answers above:
#include <xercesc/framework/MemBufInputSource.hpp>
char* myXMLBufString = "<root>hello xml</root>";
MemBufInputSource xmlBuf((const XMLByte*)myXMLBufString, 23, "myXMLBufName", false);
But take note, this doesn't seem to work unless you first initialize the system, as below (taken from the xerces-c-3.2.3/samples/src/SAX2Count/SAX2Count.cpp)
bool recognizeNEL = false;
char localeStr[64];
memset(localeStr, 0, sizeof localeStr);
// Initialize the XML4C2 system
try {
if (strlen(localeStr)) {
XMLPlatformUtils::Initialize(localeStr);
} else {
XMLPlatformUtils::Initialize();
}
if (recognizeNEL) {
XMLPlatformUtils::recognizeNEL(recognizeNEL);
}
} catch (const XMLException& toCatch) {
XERCES_STD_QUALIFIER cerr << "Error during initialization! Message:\n"
<< StrX(toCatch.getMessage()) << XERCES_STD_QUALIFIER endl;
return 1;
}
Of course reading a file wouldn't require thinking about this type of prep since you just pass a file path to the program which the parser takes. So for those experiencing seg faults, this could be the answer.
I am using jsonc-libjson to create a json string like below.
{ "author-details": {
"name" : "Joys of Programming",
"Number of Posts" : 10
}
}
My code looks like below
json_object *jobj = json_object_new_object();
json_object *jStr1 = json_object_new_string("Joys of Programming");
json_object *jstr2 = json_object_new_int("10");
json_object_object_add(jobj,"name", jStr1 );
json_object_object_add(jobj,"Number of Posts", jstr2 );
this gives me json string
{
"name" : "Joys of Programming",
"Number of Posts" : 10
}
How do I add the top part associated with author details?
To paraphrase an old advertisement, "libjson users would rather fight than switch."
At least I assume you must like fighting with the library. Using nlohmann's JSON library, you could use code like this:
nlohmann::json j {
{ "author-details", {
{ "name", "Joys of Programming" },
{ "Number of Posts", 10 }
}
}
};
At least to me, this seems somewhat simpler and more readable.
Parsing is about equally straightforward. For example, let's assume we had a file named somefile.json that contained the JSON data shown above. To read and parse it, we could do something like this:
nlohmann::json j;
std::ifstream in("somefile.json");
in >> j; // Read the file and parse it into a json object
// Let's start by retrieving and printing the name.
std::cout << j["author-details"]["name"];
Or, let's assume we found a post, so we want to increment the count of posts. This is one place that things get...less tasteful--we can't increment the value as directly as we'd like; we have to obtain the value, add one, then assign the result (like we would in lesser languages that lack ++):
j["author-details"]["Number of Posts"] = j["author-details"]["Number of Posts"] + 1;
Then we want to write out the result. If we want it "dense" (e.g., we're going to transmit it over a network for some other machine to read it) we can just use <<:
somestream << j;
On the other hand, we might want to pretty-print it so a person can read it more easily. The library respects the width we set with setw, so to have it print out indented with 4-column tab stops, we can do:
somestream << std::setw(4) << j;
Create a new JSON object and add the one you already created as a child.
Just insert code like this after what you've already written:
json_object* root = json_object_new_object();
json_object_object_add(root, "author-details", jobj); // This is the same "jobj" as original code snippet.
Based on the comment from Dominic, I was able to figure out the correct answer.
json_object *jobj = json_object_new_object();
json_object* root = json_object_new_object();
json_object_object_add(jobj, "author-details", root);
json_object *jStr1 = json_object_new_string("Joys of Programming");
json_object *jstr2 = json_object_new_int(10);
json_object_object_add(root,"name", jStr1 );
json_object_object_add(root,"Number of Posts", jstr2 );
I'm using Casablanca, cpprestsdk to consume REST APIs in C++, in Visual Studio 2015 Professional. I'm trying to develop a simple example here hitting an API and parsing the response as JSON. The URL I'm using, actually returns all the parameters sent to the API.
I've hit the API and got response as well, extracted json from the response successfully. But when i try to read a value at any key from json, it crashes. Hence i put a check whether that key is available or not, and it always says json does not have the field. As an example i printed the data i.e. json. It has the key/field "name" but when i check it via has_field, it returns false.
Please help.
Complete code is below :
json::value postData;
postData[L"name"] = json::value::string(L"Joe Smith");
postData[L"sport"] = json::value::string(L"Baseball");
http_client client(L"https://httpbin.org/post);
http_request request(methods::POST);
request.set_body(postData);
client.request(request).then([](web::http::http_response response) {
json::value j = response.extract_json().get();
json::value data = j.at(U("data"));
std::wcout << "Json : " << data;
// Prints "{\"name\":\"Joe Smith\",\"sport\":\"Baseball\"}"
if (data.has_field(U("name"))) {
std::cout << "Name Found";
}
else {
std::cout << "Name key not Found";
}
});
It seems that your response looks like this:
{ "data": "{\"name\":\"Joe Smith\",\"sport\":\"Baseball\"}" }`
i.e. the actual data is not a JSon object but escaped JSon passed as string. I guess you need to return a payload that looks like this to do what you want to do the way you are doing it:
{
"data": {
"name": "John Smith",
"sport": "Baseball"
}
}
Hei , I have this text in a JSON :
( without the returns all in one line)
[
{
"ERROR":false,
"USERNAME":"Benutzer",
"FORMAT":"HUMAN",
"LATITUDE_MIN":84,
"LATITUDE_MAX":36,
"LONGITUDE_MIN":5,
"LONGITUDE_MAX":20,
"RECORDS":203
},
[
{
"MMSI":233434540,
"TIME":"2014-10-09 06:19:06 GMT",
"LONGITUDE":8.86037,
"LATITUDE":54.12666,
"COG":347,
"SOG":0,
"HEADING":236,
"NAVSTAT":0,
"IMO":0,
"NAME":"HELGOLAND",
"CALLSIGN":"DK6068",
"TYPE":90,
"A":20,
"B":15,
"C":4,
"D":4,
"DRAUGHT":2,
"DEST":"BREMERHAVEN",
"ETA":"00-00 00:00"
},
{
"MMSI":319072300,
"TIME":"2014-10-09 06:08:53 GMT",
"LONGITUDE":9.71578,
"LATITUDE":54.31949,
"COG":343.6,
"SOG":0,
"HEADING":197,
"NAVSTAT":5,
"IMO":1012189,
"NAME":"M.Y. ESTER III",
"CALLSIGN":"ZGED3",
"TYPE":37,
"A":31,
"B":35,
"C":7,
"D":6,
"DRAUGHT":3.5,
"DEST":"SCHACT AUDORF",
"ETA":"09-16 08:00"
}
// many more lines but the Json IS VALID.
]
]
I would parse it and put that in a MYSQL table.
Not all, only name and MMSI first.
But this don't view anything in my consle because its dont jump in the foreach:
bool ok = true;
// my json data is in reply & ok is a boolean
QVariantList result = parser.parse(reply, &ok).toList();
foreach(QVariant record, result) {
QVariantMap map = record.toMap();
qDebug() << map.value("NAME");
}
What's wrong ?
When i debug, i only see that it doesn't jump in the foreach.
I use the QJson libary : QJson::Parser parser; But please anyone can tell me what i do wrong?
Your code looks like you are iterating over top level array, while the data you are looking for is in the nested array, which is effectively the second item of the top level array. So, you need to iterate over items in the inner array.
The following code works for me with your sample JSON:
QVariantList result = parser.parse(reply, &ok).toList().at(1).toList();
foreach (const QVariant &item, result) {
QVariantMap map = item.toMap();
qDebug() << map["NAME"].toString();
qDebug() << map["MMSI"].toLongLong();
}
If you are using Qt5 or above, you can make use of the awesome features provided by QJsonDocument, QJsonObject and QJsonArray.
I have copied your json into a file named test.txt in my D-drive and the code below works fine.
QJsonDocument jsonDoc;
QByteArray temp;
QFile file("D://test.txt");
if (file.open(QIODevice::ReadOnly | QIODevice::Text))
{
temp = file.readAll();
}
jsonDoc = QJsonDocument::fromJson(temp);
QJsonArray jsonArray = jsonDoc.array().at(1).toArray(); //Since you are interested in the json array which is the second item and not the first json object with error
for(int i =0; i < jsonArray.size(); ++i)
{
QJsonObject jsonObj = jsonArray.at(i).toObject();
int mmsi = jsonObj.find("MMSI").value().toInt();
QString name = jsonObj.find("NAME").value().toString();
qDebug() << mmsi;
qDebug() << name;
}
If you have to stick to Qt4, you can try using the qjson4 library which tries to mimic the behavior of the 'QJsonDocument' which is part of Qt5.
I know how to create a complete dom from an xml file just using XercesDOMParser:
xercesc::XercesDOMParser parser = new xercesc::XercesDOMParser();
parser->parse(path_to_my_file);
parser->getDocument(); // From here on I can access all nodes and do whatever i want
Well, that works... but what if I'd want to parse a string? Something like
std::string myxml = "<root>...</root>";
xercesc::XercesDOMParser parser = new xercesc::XercesDOMParser();
parser->parse(myxml);
parser->getDocument(); // From here on I can access all nodes and do whatever i want
I'm using version 3. Looking inside the AbstractDOMParser I see that parse method and its overloaded versions, only parse files.
How can I parse from a string?
Create a MemBufInputSource and parse that:
xercesc::MemBufInputSource myxml_buf(myxml.c_str(), myxml.size(),
"myxml (in memory)");
parser->parse(myxml_buf);
Use the following overload of XercesDOMParser::parse():
void XercesDOMParser::parse(const InputSource& source);
passing it a MemBufInputSource:
MemBufInputSource src((const XMLByte*)myxml.c_str(), myxml.length(), "dummy", false);
parser->parse(src);
Im doing it another way. If this is incorrect, please tell me why. It seems to work.
This is what parse expects:
DOMDocument* DOMLSParser::parse(const DOMLSInput * source )
So you need to put in a DOMLSInput instead of a an InputSource:
xercesc::DOMImplementation * impl = xercesc::DOMImplementation::getImplementation();
xercesc::DOMLSParser *parser = (xercesc::DOMImplementationLS*)impl)->createLSParser(xercesc::DOMImplementation::MODE_SYNCHRONOUS, 0);
xercesc::DOMDocument *doc;
xercesc::Wrapper4InputSource source (new xercesc::MemBufInputSource((const XMLByte *) (myxml.c_str()), myxml.size(), "A name");
parser->parse(&source);
You may use MemBufInputSource as found in the xercesc/framework/MemBufInputSource.cpp, and the header file, MemBufInputSource.hpp contains extensive documentation, as similar to answers above:
#include <xercesc/framework/MemBufInputSource.hpp>
char* myXMLBufString = "<root>hello xml</root>";
MemBufInputSource xmlBuf((const XMLByte*)myXMLBufString, 23, "myXMLBufName", false);
But take note, this doesn't seem to work unless you first initialize the system, as below (taken from the xerces-c-3.2.3/samples/src/SAX2Count/SAX2Count.cpp)
bool recognizeNEL = false;
char localeStr[64];
memset(localeStr, 0, sizeof localeStr);
// Initialize the XML4C2 system
try {
if (strlen(localeStr)) {
XMLPlatformUtils::Initialize(localeStr);
} else {
XMLPlatformUtils::Initialize();
}
if (recognizeNEL) {
XMLPlatformUtils::recognizeNEL(recognizeNEL);
}
} catch (const XMLException& toCatch) {
XERCES_STD_QUALIFIER cerr << "Error during initialization! Message:\n"
<< StrX(toCatch.getMessage()) << XERCES_STD_QUALIFIER endl;
return 1;
}
Of course reading a file wouldn't require thinking about this type of prep since you just pass a file path to the program which the parser takes. So for those experiencing seg faults, this could be the answer.