C + + reads and writes JSON files through the Jsoncpp class library

JSON is a lightweight data definition format, easy to learn and use than XML, and the extension is not much worse than XML, data exchange is a good choice. The full name of JSON is: JavaScript Object Notation, as the name implies, JSON is used to mark JavaScript objects, the details refer to http://www.json.org/.

This tutorial chooses third-party library jsoncpp to parse JSON, Jsoncpp is a more famous C + + analytic library, which is also the most popular in the JSON website.

jsoncpp:http://download.csdn.net/detail/tennysonsky/

After downloading the source code to extract the jsoncpp-src-0.5.0 folder, we only need jsoncpp header files and CPP files, where Jsonscpp header files are located in Jsoncpp-src-0.5.0\include\json, The Jsoncpp CPP file is located in Jsoncpp-src-0.5.0\src\lib_json.

JSON: The header file required for JSON operation, this folder name cannot be modified because the. cpp in the Lib_json directory contains the header file form: #include <json/xxx.h>.

Lib_json: The CPP file required for JSON operation, the name of this folder can be named according to your needs.

Copy the JSON and Lib_json into the directory where you need to write the code ( Note : JSON and Lib_json are in the same level directory ):

When compiling the code, the CPP file in the Lib_json directory needs to be added to the compilation condition:

1) Read JSON from the string

#include <string> #include <json/json.h> #include <iostream> #include <fstream>using namespace Std;void Readstrjson (); Reads the jsonvoid Readstrprojson () from the string; Read JSON from string (more complex) int main (int argc, char *argv[]) {Readstrjson (); cout << "\ n"; Readstrprojson (); return 0;} Read from String jsonvoid Readstrjson () {//string const char* str = "{\" praenomen\ ": \" gaius\ ", \" nomen\ ": \" julius\ ", \" cognomen\        ": \" Caezar\ "," "\" born\ ": -100,\" died\ ":-44}"; /*//json content as follows: {"praenomen": "Gaius", "nomen": "Julius", "cognomen": "Caezar", "Born": -100, "died": -44} */Json::reader  Reader  Json::value Root;      Read data from String if (Reader.parse (Str,root)) {string praenomen = root["praenomen"].asstring ();      string nomen = root["nomen"].asstring ();      String cognomen = root["cognomen"].asstring ();      int born = root["Born"].asint ();      int died = root["died"].asint (); cout << praenomen + "" + nomen + "" + cognomen << "is born in year" << BorN << ", died in year" << died << Endl; }//read JSON from string (more complex) void Readstrprojson () {string strvalue = "{\" name\ ": \" json\ ", \" array\ ": [{\" cpp\ ": \" Jsoncpp\ "} {\ "java\": \ "Jsoninjava\"},{\ "php\": \ "Support\"}]} ";/*//json content is as follows: {" name ":" Json″, "" Array ": [{" C    PP ":" Jsoncpp "}, {" Java ":" Jsoninjava "}, {" PHP ":" Support "} ]}*/json::reader Reader; Json::value value;if (Reader.parse (strvalue, Value)) {string out = value[' name '].asstring () cout << out << Endl;const json::value arrayobj = value["Array"];for (unsigned int i = 0; i < arrayobj.size (); i++) {if (!arrayobj[i].is Member ("CPP")) Continue;out = arrayobj[i]["cpp"].asstring () cout << out;if (i! = (Arrayobj.size ()-1)) cout <&lt ; Endl;}}}

The results of the compilation run are as follows:

2) Read JSON from the file

#include <string> #include <json/json.h> #include <iostream> #include <fstream>using namespace Std;void Readfilejson (); Read JSON from the file, a file that stores the JSON format string int main (int argc, char *argv[]) {Readfilejson (); return 0;} Read Jsonvoid Readfilejson () {Json::reader reader from the file; Json::value root;//read from the file to ensure that the current file has Test.json file Ifstream in ("Test.json", ios::binary);//in.open ("Test.json", iOS:: binary); if (!in.is_open ()) {cout << "Error opening file\n"; return;} The/*//test.json contents are as follows: {"name": "Tsybius", "age": All, "Sex_is_male": true, "partner": {"Partner_name": "Galatea", "Partner_ Age ": +," Partner_sex_is_male ": false}," Achievement ": [" Ach1 "," Ach2 "," Ach3 "]}*/if (Reader.parse (in,root)) {// Read the root node information string name = root["Name"].asstring (); int = root["Age"].asint (); bool Sex_is_male = root["Sex_is_male"]. Asbool () cout << "My name is" << name << endl;cout << "I ' m" << age << "years old" & lt;< endl;cout << "I ' m A" << (Sex_is_male? ") Man ":" Woman ") << endl;//read child node information string partner_name = root["partner" ["Partner_name"].asstring (); int partner_age = root["partner"] ["Partner_age"].asint (); bool Partner_sex_is_male = root["partner" ["Partner_sex_is_male"].asbool (); cout << " My Partner ' s name is ' << partner_name << endl;cout << (partner_sex_is_male? " He ":" she ") <<" is "<< partner_age <<" years old "<< endl;//read array information cout <<" Here's my Achi Evements: "<< endl;for (unsigned int i = 0; I < root["Achievement"].size (); i++) {String ach = root["achievement"][i].asstring (); cout << ach << ' \ t ';} cout << endl;cout << "Reading complete!" << Endl;} Else{cout << "Parse error\n" << Endl;} In.close ();}

The contents of the Test.json file are as follows:

{"Name": "Mike Jiang", "age": +, "Sex_is_male": true, "partner": {    "partner_name": "Galatea",    "Partner_age": 21 ,    "Partner_sex_is_male": false}, "Achievement": ["Ach1", "Ach2", "Ach3"]}

The results of the compilation run are as follows:

3) Save the information in JSON format

#include <string> #include <json/json.h> #include <iostream> #include <fstream>using namespace Std;void Writefilejson ();//Save the information in JSON format int main (int argc, char *argv[]) {Writefilejson (); return 0;} Save information in Json format void Writefilejson () {///root node Json::value root;//root node property root["Name"] = Json::value ("Mike Jiang"); root["Age" ] = Json::value (root["sex_is_male"] = Json::value (TRUE);//child node Json::value partner;//child node Property partner["Partner_name"] = Json::value ("Galatea");p artner["partner_age"] = Json::value (+);p artner["Partner_sex_is_male"] = Json::value ( FALSE);//The child node is hung on the root node root["partner"] = Json::value (partner);//Array Form root["Achievement"].append ("Ach1"); root[" Achievement "].append (" Ach2 ") root[" Achievement "].append (" Ach3 ");//Direct output cout <<" Fastwriter: "<< Endl; Json::fastwriter fw;cout << fw.write (root) << Endl << endl;//indent output cout << "Styledwriter:" < < Endl; Json::styledwriter sw;cout << sw.write (root) << Endl << endl;//output to file Ofstream Os;os. Open ("Demo.json"); OS << sw.write (root); Os.close ();/*//json file contents are as follows: {"Achievement": ["Ach1", "Ach2", "Ach3"], " Age ":", "name": "Mike Jiang", "partner": {"partner_age": +, "partner_name": "Galatea", "Partner_sex_is_male": false}, "Sex_is_male": true}*/}

The results of the compilation run are as follows:

The contents of the generated Demo.json file are as follows:

This tutorial sample code download Please click this link: Http://download.csdn.net/detail/tennysonsky

Resources:

Http://www.cnblogs.com/ggjucheng

http://my.oschina.net/Tsybius2014

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C + + reads and writes JSON files through the Jsoncpp class library