C、C++中对json格式数据的解析和封装
C:首先需要调库：#include <cJSON.h>
Json的数据结构介绍：
/* The cJSON structure: */
typedef struct cJSON
{
/*next/prev允许您遍历数组/对象链。或者，使用GetArraySize/GetArrayItem/GetObjectItem */
struct cJSON *next;
struct cJSON *prev;
/* 数组或对象项将有一个子指针指向数组/对象中的项链。 */
struct cJSON *child;
/* 项目的类型，如上所述。*/
int type;
/* 字符串, if type==cJSON_String */
char *valuestring;
/* 数值, if type==cJSON_Number */
int valueint;
/* 小数数据, if type==cJSON_Number */
double valuedouble;
/* 项的名称字符串，如果此项是的子项，或在对象的子项列表中。*/
char *string;
} cJSON;Json格式文本解析：
#define TEST2 "{n"auth": "auc_d0dd49997dd17b12f76b74fe51d0de3fd772718b",n"sessionId": "5129110798518519880764729435382"n}"
char* buffer = TEST2;
cJSON* json = cJSON_Parse(buffer);
cJSON* name = cJSON_GetObjectItem(json, "name");
cJSON* num = cJSON_GetObjectItem(json, "num");
printf("%s,%s",name->valuestring,num->valueint);
假设文本为：需要解析中间的pinyin,textContent,title
"Data":
{
"listItems":
[
{
"htmlView":"http://hanyu.baidu.com/s?wd=一飞冲天&ptype=zici",
"mediaId":"6f7af22ba4613b869f455d569c204c69",
"selfData":"{"interpretation":"鸟儿展翅一飞，直冲云霄。比喻平时没有特殊表现，一下做出了惊人的成绩。","lemma":"一飞冲天","pinyin":"[yī fēi chōng tiān]"}n",
"textContent":"鸟儿展翅一飞，直冲云霄。比喻平时没有特殊表现，一下做出了惊人的成绩。",
"title":"一飞冲天"
}
]
}
cJSON* Data = cJSON_GetObjectItem(json, "Data");
cJSON* ListItems = cJSON_GetObjectItem(Data, "listItems");
cJSON* Json_Array = cJSON_GetArrayItem(ListItems, 0);//其中[]里面为数组需要用cJSON_GetArrayItem，0代表第一个。
cJSON* TextContent = cJSON_GetObjectItem(Json_Array, "textContent");
cJSON* Title = cJSON_GetObjectItem(Json_Array, "title");
cJSON* SelfData = cJSON_GetObjectItem(Json_Array, "selfData");
cJSON* Src = cJSON_Parse(SelfData->valuestring);//selfData数据解析出来为字符串，需要再次解析为json数据才能再次解析
cJSON* Pinyin = cJSON_GetObjectItem(Src, "pinyin");Json格式文本封装：将多条字符串合成一条json格式数据
const char* client_id = "12345678";
const char* sessionid = "abcdefg";
cJSON *root = cJSON_CreateObject();
cJSON_AddStringToObject(root, "authCode", client_id);
cJSON_AddStringToObject(root, "sessionId", sessionid);//这里的添加处理字符串以外还可以添加很多类型的数据
char *auth_resp_info = cJSON_Print(root);
printf("%s,%s",auth_resp_info);C++封装json格式数据:
创建一个C++类来封装这个JSON数据：
#include <iostream>
#include <string>
#include <vector>
class Address {
public:
std::string street;
std::string city;
};
class Person {
public:
std::string name;
int age;
Address address;
std::vector<std::string> hobbies;
};
int main() {
Person person;
person.name = "John";
person.age = 30;
person.address.street = "123 Main St";
person.address.city = "New York";
person.hobbies = {"Reading", "Hiking"};
// 将Person对象转换为JSON字符串
nlohmann::json j;
j["person"]["name"] = person.name;
j["person"]["age"] = person.age;
j["person"]["address"]["street"] = person.address.street;
j["person"]["address"]["city"] = person.address.city;
j["person"]["hobbies"] = person.hobbies;
std::string jsonStr = j.dump();
std::cout << jsonStr << std::endl;
return 0;
}
最后的数据为：
{
"person": {
"name": "John",
"age": 30,
"address": {
"street": "123 Main St",
"city": "New York"
},
"hobbies": ["Reading", "Hiking"]
}
}
还有些栗子：
json json_data;
json_data["Header"] = {{"DSN","5ca439320d7b4adfb965a4442c791c33"}};
json_data["Payload"] = {{"blobData",{{"longitude",""},{"latitude",""}}},{"domain","weather"},{"intent","GetGeneralMsgRequest"}};
最后形成：
JSON string: {
"Header": {
"DSN": "5ca439320d7b4adfb965a4442c791c33"
},
"Payload": {
"blobData": {
"latitude": "",
"longitude": ""
},
"domain": "weather",
"intent": "GetGeneralMsgRequest"
}
}
或者可以这样：也可以形成上面的数据
json j2 = R"(
"Header": {
"DSN": "5ca439320d7b4adfb965a4442c791c33"
},
"Payload": {
"blobData": {
"latitude": "",
"longitude": ""
},
"domain": "weather",
"intent": "GetGeneralMsgRequest"
}
)"_json;
要想打印上面封装的json的数据可以用以字符串的形式：
json_data.dump(4)C++解析json格式数据:
1、RapidJSON：RapidJSON是一个非常快速的JSON解析库，它提供了简单的API来解析和生成JSON数据。
示例代码：
#include "rapidjson/document.h"
#include "rapidjson/writer.h"
#include "rapidjson/stringbuffer.h"
#include <iostream>
#include <string>
int main() {
const char* json = "{"name":"John","age":30,"city":"New York"}";
rapidjson::Document doc;
doc.Parse(json);
if (!doc.HasParseError()) {
std::string name = doc["name"].GetString();
int age = doc["age"].GetInt();
std::string city = doc["city"].GetString();
std::cout << "Name: " << name << ", Age: " << age << ", City: " << city << std::endl;
} else {
std::cout << "JSON parse error" << std::endl;
}
return 0;
}
2、JSON for Modern C++ (nlohmann/json)：这是一个现代C++中使用的非常流行的JSON解析库。它提供了简单的API和STL兼容性，容易学习和使用。
示例代码：
#include <nlohmann/json.hpp>
#include <iostream>
#include <string>
int main() {
std::string json = "{"name":"John","age":30,"city":"New York"}";
nlohmann::json j = nlohmann::json::parse(json);
std::string name = j["name"];
int age = j["age"];
std::string city = j["city"];
std::cout << "Name: " << name << ", Age: " << age << ", City: " << city << std::endl;
return 0;
}
C++中解析多重json格式的数据：
在C++中获取多重JSON格式的数据，你需要逐级解析JSON结构，以访问嵌套在JSON对象或数组中的数据。以下是一个示例，演示如何处理多重嵌套的JSON数据。
假设你有以下JSON数据：
{
"person": {
"name": "John",
"age": 30,
"address": {
"street": "123 Main St",
"city": "New York"
},
"hobbies": ["Reading", "Hiking"]
}
}
你可以使用RapidJSON或nlohmann/json等JSON解析库来处理这个JSON数据。
使用RapidJSON的示例代码：
#include "rapidjson/document.h"
#include "rapidjson/writer.h"
#include "rapidjson/stringbuffer.h"
#include <iostream>
#include <string>
int main() {
const char* json = "{"person":{"name":"John","age":30,"address":{"street":"123 Main St","city":"New York"},"hobbies":["Reading","Hiking"]}}";
rapidjson::Document doc;
doc.Parse(json);
if (!doc.HasParseError()) {
const rapidjson::Value& person = doc["person"];
std::string name = person["name"].GetString();
int age = person["age"].GetInt();
const rapidjson::Value& address = person["address"];
std::string street = address["street"].GetString();
std::string city = address["city"].GetString();
const rapidjson::Value& hobbies = person["hobbies"];
if (hobbies.IsArray()) {
for (rapidjson::SizeType i = 0; i < hobbies.Size(); i++) {
std::string hobby = hobbies[i].GetString();
std::cout << "Hobby " << i + 1 << ": " << hobby << std::endl;
}
}
std::cout << "Name: " << name << ", Age: " << age << std::endl;
std::cout << "Address: " << street << ", " << city << std::endl;
} else {
std::cout << "JSON parse error" << std::endl;
}
return 0;
}
使用nlohmann/json的示例代码：
#include <nlohmann/json.hpp>
#include <iostream>
#include <string>
int main() {
std::string json = "{"person":{"name":"John","age":30,"address":{"street":"123 Main St","city":"New York"},"hobbies":["Reading","Hiking"]}}";
nlohmann::json j = nlohmann::json::parse(json);
std::string name = j["person"]["name"];
int age = j["person"]["age"];
std::string street = j["person"]["address"]["street"];
std::string city = j["person"]["address"]["city"];
for (const auto& hobby : j["person"]["hobbies"]) {
std::string hobbyStr = hobby;
std::cout << "Hobby: " << hobbyStr << std::endl;
}
std::cout << "Name: " << name << ", Age: " << age << std::endl;
std::cout << "Address: " << street << ", " << city << std::endl;
return 0;
}
#include <nlohmann/json.hpp>
#include <iostream>
#include <string>
int main() {
std::string json = R"(
{
"Header": {
"sessionId": "1648612124933560_v20ZmHxNa4yx3",
"code": 200,
"message": "业务服务返回消息:StatusOK"
},
"Payload": {
"groupList": [
{
"groupName": "巅峰榜",
"groupTopList": [
{
"listenNum": 18835312,
"showTime": "2022-03-30",
"songInfos": [
{
"singerId": 4658,
"singerMId": "000ZVS6E1f6f0d",
"singerName": "杨丞琳",
"songId": 648765,
"songMId": "004XNJ8Y2iD3VL",
"songName": "匿名的好友"
},
{
"singerId": 143,
"singerMId": "003Nz2So3XXYek",
"singerName": "陈奕迅",
"songId": 331839675,
"songMId": "003UkWuI0E8U0l",
"songName": "孤勇者"
}
],
"topBannerPic": "http://y.gtimg.cn/music/photo_new/T003R500x500M000001namcx2Rs3fW.jpg",
"topHeaderPic": "http://y.gtimg.cn/music/photo_new/T002R300x300M000000jcKFG0sQrD0.jpg",
"topId": 62,
"topName": "飙升榜",
"totalNum": 100
}
]
}
],
"msg": "OK",
"ret": 0,
"sessionId": "1648612124933560_v20ZmHxNa4yx3"
}
}
)";
nlohmann::json j = nlohmann::json::parse(json);
if (j.contains("Header") && j.contains("Payload")) {
const auto& header = j["Header"];
const auto& payload = j["Payload"];
std::string sessionId = header["sessionId"];
int code = header["code"];
std::string message = header["message"];
std::string msg = payload["msg"];
int ret = payload["ret"];
std::string payloadSessionId = payload["sessionId"];
const auto& groupList = payload["groupList"];
if (groupList.is_array()) {
for (const auto& group : groupList) {
std::string groupName = group["groupName"];
const auto& groupTopList = group["groupTopList"];
if (groupTopList.is_array()) {
for (const auto& top : groupTopList) {
int listenNum = top["listenNum"];
std::string showTime = top["showTime"];
int topId = top["topId"];
std::string topName = top["topName"];
int totalNum = top["totalNum"];
const auto& songInfos = top["songInfos"];
if (songInfos.is_array()) {
for (const auto& songInfo : songInfos) {
int singerId = songInfo["singerId"];
std::string singerMId = songInfo["singerMId"];
std::string singerName = songInfo["singerName"];
int songId = songInfo["songId"];
std::string songMId = songInfo["songMId"];
std::string songName = songInfo["songName"];
// 打印解析结果
std::cout << "Song Info:" << std::endl;
std::cout << "Singer ID: " << singerId << std::endl;
std::cout << "Singer MId: " << singerMId << std::endl;
std::cout << "Singer Name: " << singerName << std::endl;
std::cout << "Song ID: " << songId << std::endl;
std::cout << "Song MId: " << songMId << std::endl;
std::cout << "Song Name: " << songName << std::endl;
}
} else {
std::cout << "songInfos is not an array" << std::endl;
}
// 打印解析结果
std::cout << "Listen Num: " << listenNum << std::endl;
std::cout << "Show Time: " << showTime << std::endl;
std::cout << "Top ID: " << topId << std::endl;
std::cout << "Top Name: " << topName << std::endl;
std::cout << "Total Num: " << totalNum << std::endl;
}
} else {
std::cout << "groupTopList is not an array" << std::endl;
}
// 打印解析结果
std::cout << "Group Name: " << groupName << std::endl;
}
} else {
std::cout << "groupList is not an array" << std::endl;
}
} else {
std::cout << "Header or Payload is not present in the JSON" << std::endl;
}
return 0;
}
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