源码下载：GitHub - dropbox/json11: A tiny JSON library for C++11.
1.加载json11库
它用起来非常方便,只有两个文件，一个json11.hpp，一个json11.cpp。
2.代码示例
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include "json11.hpp"
#ifdef _MSC_VER
#include <Windows.h>
static std::string utf8_to_gbk(const char *utf8)
{
char gbk[256];
const int maxlen = 256;
wchar_t unicode_str[maxlen];
int outlen = MultiByteToWideChar(CP_UTF8, 0, utf8, strlen(utf8), unicode_str, maxlen);
outlen = WideCharToMultiByte(CP_ACP, 0, unicode_str, outlen, gbk, 256, NULL, NULL);
gbk[outlen] = '\0';
std::string str;
str.assign(gbk);
return str;
}
#endif
int test1();
int test2();
int test3();
int test4();
int main()
{
test4();
std::cout << "ok" << std::endl;
return 0;
}
int test4()
{
// std::istringstream
std::filebuf in;
if (!in.open("E:/GitCode/Messy_Test/testdata/json.data", std::ios::in))
{
std::cout << "fail to open file" << std::endl;
return -1;
}
std::istream iss(&in);
std::istreambuf_iterator<char> eos;
std::string s(std::istreambuf_iterator<char>(iss), eos);
std::string err;
auto json = json11::Json::parse(s, err);
if (!err.empty())
{
in.close();
return -1;
}
std::cout << "************** show file info *****************" << std::endl;
std::string json_str = json.dump();
std::cout << json_str << std::endl;
std::cout << "*************** start parse ****************" << std::endl;
std::string name = json["name"].string_value();
std::string addr = json["address"].string_value();
int age = json["age"].int_value();
json11::Json::array array_ = json["value1"].array_items();
std::vector<std::vector<float>> value1;
value1.resize(array_.size());
for (int i = 0; i < array_.size(); i++)
{
json11::Json::array tmp = array_[i].array_items();
value1[i].resize(tmp.size());
for (int j = 0; j < tmp.size(); j++)
{
value1[i][j] = tmp[j].number_value();
}
}
std::vector<float> value2;
array_ = json["value2"].array_items();
value2.resize(array_.size());
for (int i = 0; i < array_.size(); i++)
{
value2[i] = array_[i].number_value();
}
std::string beijing_addr;
bool beijing_car, beijing_cat;
if (json["bei_jing"].is_null())
{
std::cout << "failed to get bei_jing info" << std::endl;
}
else
{
json11::Json::object object_ = json["bei_jing"].object_items();
beijing_addr = object_["address"].string_value();
beijing_car = object_["car"].bool_value();
beijing_cat = object_["cat"].bool_value();
}
std::string shandong_addr, tmp_addr;
std::vector<std::string> shandong_value1;
if (json["shan_dong"].is_null())
{
std::cout << "failed to get shan_dong info" << std::endl;
}
else
{
json11::Json::object object_ = json["shan_dong"].object_items();
tmp_addr = object_["tmp"].string_value();
if (tmp_addr == "")
{
std::cout << "tmp is null" << std::endl;
}
shandong_addr = object_["address"].string_value();
json11::Json::array tmp = object_["value1"].array_items();
shandong_value1.resize(array_.size());
json11::Json json_ = tmp[0];
shandong_value1[0] = json_["ji_nan"].string_value();
json_ = tmp[1];
shandong_value1[1] = json_["tai_an"].string_value();
}
std::cout << "************** parse result ***************" << std::endl;
std::cout << "name: " << utf8_to_gbk(name.c_str()) << std::endl;
std::cout << "address: " << utf8_to_gbk(addr.c_str()) << std::endl;
std::cout << "age: " << age << std::endl;
std::cout << "value1: " << std::endl;
for (int i = 0; i < value1.size(); i++)
{
for (int j = 0; j < value1[i].size(); j++)
{
std::cout << " " << value1[i][j];
}
std::cout << std::endl;
}
std::cout << "value2: " << std::endl;
for (int i = 0; i < value2.size(); i++)
{
std::cout << " " << value2[i];
}
std::cout << std::endl;
std::cout << "bei_jing info: " << std::endl;
std::cout << " address: " << utf8_to_gbk(beijing_addr.c_str()) << std::endl;
std::cout << " car: " << beijing_car << std::endl;
std::cout << " cat: " << beijing_cat << std::endl;
std::cout << "shan_dong info: " << std::endl;
std::cout << " address: " << utf8_to_gbk(shandong_addr.c_str()) << std::endl;
std::cout << " value1: " << std::endl;
std::cout << " ji_nan: " << utf8_to_gbk(shandong_value1[0].c_str()) << std::endl;
std::cout << " tai_an: " << utf8_to_gbk(shandong_value1[1].c_str()) << std::endl;
in.close();
return 0;
}
int test1()
{
json11::Json my_json = json11::Json::object{
{"中国", "北京"},
{"key2", false},
{"key3", json11::Json::array{1, 2, 3}},
};
std::string json_str = my_json.dump();
std::string key_1 = my_json["中国"].string_value();
std::cout << json_str << std::endl;
std::cout << key_1 << std::endl;
return 0;
}
int test2()
{
class Point
{
public:
int x;
int y;
Point(int x, int y) : x(x), y(y) {}
json11::Json to_json() const { return json11::Json::array{x, y}; }
};
std::vector<Point> points = {{1, 2}, {10, 20}, {100, 200}};
std::string points_json = json11::Json(points).dump();
std::cout << points_json << std::endl;
return 0;
}
int test3()
{
json11::Json json = json11::Json::array{json11::Json::object{{"k", "v"}}};
std::string str = json[0]["k"].string_value();
std::cout << str << std::endl;
return 0;
}json文件内容如下所示：
{
"name": "spring",
"address": "北京",
"age": 30,
"value1": [
[
23,
43,
-2.3,
6.7,
90
],
[
-9,
-19,
10,
2
],
[
-5,
-55
]
],
"value2": [
13.3,
1.9,
2.10
],
"bei_jing": {
"address": "海淀",
"car": false,
"cat": true
},
"shan_dong": {
"address": "济南",
"value1": [
{
"ji_nan": "趵突泉"
},
{
"tai_an": "泰山"
}
]
}
}