Cpp中使用RapidJSON
作者：互联网
简介
官方参考文档：http://rapidjson.org/zh-cn/index.html
RapidJSON是腾讯开源的一个高效的C++ JSON解析器及生成器，它是只有头文件的C++库。RapidJSON是跨平台的，支持Windows, Linux, Mac OS X及iOS, Android。它的源码在https://github.com/Tencent/rapidjson/
解析JSON
简单例子
#include "rapidjson/document.h"
#include "rapidjson/writer.h"
#include "rapidjson/stringbuffer.h"
#include <iostream>
using namespace rapidjson;
int main() {
// 1. 把 JSON 解析至 DOM。
const char* json = "{\"project\":\"rapidjson工程\",\"stars\":10}";
Document d;
d.Parse(json);
// 2. 利用 DOM 作出修改。
Value& s = d["stars"];
s.SetInt(s.GetInt() + 1);
// 3. 把 DOM 转换（stringify）成 JSON。
StringBuffer buffer;
Writer<StringBuffer> writer(buffer);
d.Accept(writer);
std::string sJson = buffer.GetString();
std::cout << sJson.c_str() << std::endl;
return 0;
}
View Code
复杂点的例子，基于Dom
#include <iostream>
#include <string>
#include "rapidjson/document.h"
/*
{
"country": "中国",
"province": [
{
"name": "黑龙江",
"cities": ["哈尔滨","大庆"]
},
{
"name": "广东",
"cities": ["广州","深圳","珠海"]
},
{
"name": "台湾",
"cities": ["台北","高雄"]
},
{
"name": "新疆",
"cities": ["乌鲁木齐"]
}
]
}
*/
int _tmain(int argc, _TCHAR* argv[])
{
const char* str = "{\"country\":\"中国\",\"province\":[{\"name\":\"黑龙江\",\"cities\":[\"哈尔滨\",\"大庆\"]},{\"name\":\"广东\",\"cities\":[\"广州\",\"深圳\",\"珠海\"]},{\"name\":\"台湾\",\"cities\":[\"台北\",\"高雄\"]},{\"name\":\"新疆\",\"cities\":[\"乌鲁木齐\"]}]}";
rapidjson::Document document;
document.Parse(str);
assert(document.IsObject());
std::string s = document["country"].GetString();
const rapidjson::Value& a = document["province"];
assert(a.IsArray());
for (rapidjson::SizeType i = 0; i < a.Size(); i++) // 使用 SizeType 而不是 size_t
{
const rapidjson::Value& b = a[i];
assert(b.IsObject());
std::string provinceName = b["name"].GetString();
std::cout << provinceName << ": ";
const rapidjson::Value& c = b["cities"];
assert(c.IsArray());
for (rapidjson::SizeType i = 0; i < c.Size(); i++)
{
std::string cityName = c[i].GetString();
std::cout << cityName << " ";
}
std::cout << "\n";
}
return 0;
}
View Code
基于SAX的解析例子
#include "rapidjson/reader.h"
#include <iostream>
#include <sstream>
using namespace rapidjson;
using namespace std;
// If you can require C++11, you could use std::to_string here
template <typename T> std::string stringify(T x) {
std::stringstream ss;
ss << x;
return ss.str();
}
struct MyHandler {
std::string type;
std::string data;
MyHandler() : type(), data() {}
bool Null() { type = "Null"; data.clear(); return true; }
bool Bool(bool b) { type = "Bool:"; data = b ? "true" : "false"; return true; }
bool Int(int i) { type = "Int:"; data = stringify(i); return true; }
bool Uint(unsigned u) { type = "Uint:"; data = stringify(u); return true; }
bool Int64(int64_t i) { type = "Int64:"; data = stringify(i); return true; }
bool Uint64(uint64_t u) { type = "Uint64:"; data = stringify(u); return true; }
bool Double(double d) { type = "Double:"; data = stringify(d); return true; }
bool RawNumber(const char* str, SizeType length, bool) { type = "Number:"; data = std::string(str, length); return true; }
bool String(const char* str, SizeType length, bool) { type = "String:"; data = std::string(str, length); return true; }
bool StartObject() { type = "StartObject"; data.clear(); return true; }
bool Key(const char* str, SizeType length, bool) { type = "Key:"; data = std::string(str, length); return true; }
bool EndObject(SizeType memberCount) { type = "EndObject:"; data = stringify(memberCount); return true; }
bool StartArray() { type = "StartArray"; data.clear(); return true; }
bool EndArray(SizeType elementCount) { type = "EndArray:"; data = stringify(elementCount); return true; }
private:
MyHandler(const MyHandler& noCopyConstruction);
MyHandler& operator=(const MyHandler& noAssignment);
};
// 从Json中根据key返回value，（只是简单的key-value，value不支持Object/Array）
std::string GetValueByKeyFromJson(const char* json, const std::string& key)
{
std::string sRet;
MyHandler handler;
rapidjson::Reader reader;
rapidjson::StringStream ss(json);
reader.IterativeParseInit();
while (!reader.IterativeParseComplete())
{
reader.IterativeParseNext<kParseDefaultFlags>(ss, handler);
if ("Key:" == handler.type)
{
if (key == handler.data)
{
reader.IterativeParseNext<kParseDefaultFlags>(ss, handler);
sRet = handler.data;
break;
}
}
}
return sRet;
}
int main() {
const char json[] = " { \"你好\" : \"中国\", \"t\" : true , \"f\" : false, \"n\": null, \"i\":123, \"pi\": 3.1415926, \"a\":[1, 2, 3, 4] } ";
std::string s = GetValueByKeyFromJson(json, "你好");//"中国"
s = GetValueByKeyFromJson(json, "pi");//"3.14159" --> 注意不是 3.1415926
s = GetValueByKeyFromJson(json, "n");//""
s = GetValueByKeyFromJson(json, "a");//""
s = GetValueByKeyFromJson(json, "t");//"true"
s = GetValueByKeyFromJson(json, "i");//"123"
return 0;
}
View Code
生成Json
////////////// 生成JSON //////////////
#include "rapidjson/writer.h"
#include "rapidjson/stringbuffer.h"
#include <iostream>
int _tmain(int argc, _TCHAR* argv[])
{
rapidjson::StringBuffer buf;
rapidjson::Writer<rapidjson::StringBuffer> writer(buf);
//rapidjson::PrettyWriter<rapidjson::StringBuffer> writer(buf); // it can word wrap
writer.StartObject(); // Between StartObject()/EndObject(),
/* writer.Key("hello"); // output a key,
writer.String("world"); // follow by a value.
writer.Key("t");
writer.Bool(true);
writer.Key("f");
writer.Bool(false);
writer.Key("n");
writer.Null();
writer.Key("i");
writer.Uint(123);
writer.Key("pi");
writer.Double(3.1416);
writer.Key("a");
writer.StartArray(); // Between StartArray()/EndArray(),
for (unsigned i = 0; i < 4; i++)
writer.Uint(i); // all values are elements of the array.
writer.EndArray();
writer.EndObject();
// {"hello":"world","t":true,"f":false,"n":null,"i":123,"pi":3.1416,"a":[0,1,2,3]}
*/
writer.Key("country"); writer.String("中国");
writer.Key("province");
writer.StartArray();
writer.StartObject();
writer.Key("name"); writer.String("黑龙江");
writer.Key("cities"); writer.StartArray(); writer.String("哈尔滨"); writer.String("大庆"); writer.EndArray();
writer.EndObject();
writer.StartObject();
writer.Key("name"); writer.String("广东");
writer.Key("cities"); writer.StartArray(); writer.String("广州"); writer.String("深圳"); writer.String("珠海"); writer.EndArray();
writer.EndObject();
writer.EndArray();
writer.EndObject();
const char* s = buf.GetString();//"{"country":"中国","province":[{"name":"黑龙江","cities":["哈尔滨","大庆"]},{"name":"广东","cities":["广州","深圳","珠海"]}]}"
std::cout << s << "\n";
return 0;
}
View Code
标签：cities,name,writer,RapidJSON,Key,使用,Cpp,include,rapidjson 来源： https://www.cnblogs.com/htj10/p/13973517.html