Correct usage of Poco C++ JSON for parsing data

Can anyone instruct me on how the Poco C++ JSON works?

Previously I've used JsonReader and JsonToken. The Poco C++ library doesn't seem to have corresponding objects.

How do I for example use the json parser to create a object name consisting the JSON value at the tag name?

2 Answers

EDIT: as of 1.5.2, things were simplified by making DefaultHandler, well ... default (and renaming it to its proper name - ParseHandler. So, if all you need is parsing, no need to explicitly provide the handler anymore:

// objects std::string json = "{ \"test\" : { \"property\" : \"value\" } }"; Parser parser; Var result = parser.parse(json); Object::Ptr object = result.extract<Object::Ptr>(); Var test = object->get("test"); object = test.extract<Object::Ptr>(); test = object->get("property"); std::string value = test.convert<std::string>(); // array of objects std::string json = "[ {\"test\" : 0}, { \"test1\" : [1, 2, 3], \"test2\" : 4 } ]"; Parser parser; Var result = parser.parse(json); Array::Ptr arr = result.extract<Array::Ptr>(); Object::Ptr object = arr->getObject(0);// assert (object->getValue<int>("test") == 0); object = arr->getObject(1); arr = object->getArray("test1"); result = arr->get(0); assert (result == 1); 

See this answer for more details.

#include <iostream> #include <string> #include <Poco/JSON/JSON.h> #include <Poco/JSON/Parser.h> #include <Poco/Dynamic/Var.h> using namespace std; using namespace Poco::JSON; string GetValue(Object::Ptr aoJsonObject, const char *aszKey) { Poco::Dynamic::Var loVariable; string lsReturn; string lsKey(aszKey); // Get the member Variable // loVariable = aoJsonObject->get(lsKey); // Get the Value from the Variable // lsReturn = loVariable.convert<std::string>(); return lsReturn; } int main(int argc, char *argv[]) { string lsJson; Parser loParser; lsJson = "{\"TransactionCode\":\"000000\",\"FileRecordSequenceNumber\":\"111111\",\"TcrSequenceNumber\":\"222222\",\"TransactionRouteIndicator\":\"ABCDE\",\"MerchantEstablishmentNumber\":\"00000000000\",\"MerchantName\":\"BBBBBBBBB\",\"MerchantCity\":\"CCCCCCCC\"}"; cout << lsJson << endl; // Parse the JSON and get the Results // Poco::Dynamic::Var loParsedJson = loParser.parse(lsJson); Poco::Dynamic::Var loParsedJsonResult = loParser.result(); // Get the JSON Object // Object::Ptr loJsonObject = loParsedJsonResult.extract<Object::Ptr>(); // Get the values for the member variables // // cout << "TransactionCode " << GetValue(loJsonObject, "TransactionCode") << endl; cout << "FileRecordSequenceNumber " << GetValue(loJsonObject, "FileRecordSequenceNumber") << endl; cout << "TcrSequenceNumber " << GetValue(loJsonObject, "TcrSequenceNumber") << endl; cout << "TransactionRouteIndicator " << GetValue(loJsonObject, "TransactionRouteIndicator") << endl; cout << "MerchantEstablishmentNumber " << GetValue(loJsonObject, "MerchantEstablishmentNumber") << endl; cout << "MerchantName " << GetValue(loJsonObject, "MerchantName") << endl; cout << "MerchantCity " << GetValue(loJsonObject, "MerchantCity") << endl; return 0; } Results: {"TransactionCode":"000000","FileRecordSequenceNumber":"111111","TcrSequenceNumber":"222222","TransactionRouteIndicator":"ABCDE","MerchantEstablishmentNumber":"00000000000","MerchantName":"BBBBBBBBB","MerchantCity":"CCCCCCCC"} TransactionCode 000000 FileRecordSequenceNumber 111111 TcrSequenceNumber 222222 TransactionRouteIndicator ABCDE MerchantEstablishmentNumber 00000000000 MerchantName BBBBBBBBB MerchantCity CCCCCCCC