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C、C++中对json格式数据的解析和封装_c++ json

作者：小蓝xlanll | 2024-05-08 09:11:02

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c++ json

C:首先需要调库：#include <cJSON.h>

  1. Json的数据结构介绍：
  2. /* The cJSON structure: */
  3. typedef struct cJSON
  4. {
  5. /*next/prev允许您遍历数组/对象链。或者，使用GetArraySize/GetArrayItem/GetObjectItem */
  6. struct cJSON *next;
  7. struct cJSON *prev;
  8. /* 数组或对象项将有一个子指针指向数组/对象中的项链。 */
  9. struct cJSON *child;
  10.  
  11. /* 项目的类型，如上所述。*/
  12. int type;
  13.  
  14. /* 字符串, if type==cJSON_String */
  15. char *valuestring;
  16. /* 数值, if type==cJSON_Number */
  17. int valueint;
  18. /* 小数数据, if type==cJSON_Number */
  19. double valuedouble;
  20.  
  21. /* 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。*/
  22. char *string;
  23. } cJSON;
  1. Json格式文本解析：
  2. #define TEST2 "{\n\"auth\": \"auc_d0dd49997dd17b12f76b74fe51d0de3fd772718b\",\n\"sessionId\": \"5129110798518519880764729435382\"\n}"
  3. char* buffer = TEST2;
  4. cJSON* json = cJSON_Parse(buffer);
  5. cJSON* name = cJSON_GetObjectItem(json, "name");
  6. cJSON* num = cJSON_GetObjectItem(json, "num");
  7. printf("%s,%s",name->valuestring,num->valueint);
  8.  
  9.  
  10. 假设文本为：需要解析中间的pinyin,textContent,title
  11. "Data":
  12.     {
  13.         "listItems":
  14. 				[
  15. 					{
  16. 						"htmlView":"http://hanyu.baidu.com/s?wd=一飞冲天&ptype=zici",
  17. 						"mediaId":"6f7af22ba4613b869f455d569c204c69",
  18. 						"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",
  19. 						"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。",
  20. 						"title":"一飞冲天"
  21. 					}
  22. 				]
  23.     }
  24.  
  25. cJSON* Data = cJSON_GetObjectItem(json, "Data");
  26. cJSON* ListItems = cJSON_GetObjectItem(Data, "listItems");
  27. 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。
  28. cJSON* TextContent = cJSON_GetObjectItem(Json_Array, "textContent");
  29. cJSON* Title = cJSON_GetObjectItem(Json_Array, "title");
  30. cJSON* SelfData = cJSON_GetObjectItem(Json_Array, "selfData");
  31. 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
  32. cJSON* Pinyin = cJSON_GetObjectItem(Src, "pinyin");
  1. Json格式文本封装：将多条字符串合成一条json格式数据
  2. const char* client_id = "12345678";
  3. const char* sessionid = "abcdefg";
  4. cJSON *root = cJSON_CreateObject();
  5. cJSON_AddStringToObject(root, "authCode", client_id);
  6. 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
  7. char *auth_resp_info = cJSON_Print(root);
  8. 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：

  1. #include <iostream>
  2. #include <string>
  3. #include <vector>
  4.  
  5. class Address {
  6. public:
  7.     std::string street;
  8.     std::string city;
  9. };
  10.  
  11. class Person {
  12. public:
  13.     std::string name;
  14.     int age;
  15.     Address address;
  16.     std::vector<std::string> hobbies;
  17. };
  18.  
  19. int main() {
  20.     Person person;
  21.     person.name = "John";
  22.     person.age = 30;
  23.     person.address.street = "123 Main St";
  24.     person.address.city = "New York";
  25.     person.hobbies = {"Reading", "Hiking"};
  26.  
  27.     // 将Person对象转换为JSON字符串
  28.     nlohmann::json j;
  29.     j["person"]["name"] = person.name;
  30.     j["person"]["age"] = person.age;
  31.     j["person"]["address"]["street"] = person.address.street;
  32.     j["person"]["address"]["city"] = person.address.city;
  33.     j["person"]["hobbies"] = person.hobbies;
  34.  
  35.     std::string jsonStr = j.dump();
  36.     std::cout << jsonStr << std::endl;
  37.  
  38.     return 0;
  39. }

 最后的数据为：

  1. {
  2.     "person": {
  3.         "name": "John",
  4.         "age": 30,
  5.         "address": {
  6.             "street": "123 Main St",
  7.             "city": "New York"
  8.         },
  9.         "hobbies": ["Reading", "Hiking"]
  10.     }
  11. }

还有些栗子： 

  1. json json_data;
  2. json_data["Header"] = {{"DSN","5ca439320d7b4adfb965a4442c791c33"}};
  3. json_data["Payload"] = {{"blobData",{{"longitude",""},{"latitude",""}}},{"domain","weather"},{"intent","GetGeneralMsgRequest"}};
  4.  
  5. 最后形成：
  6.  JSON string: {
  7.      "Header": {
  8.          "DSN": "5ca439320d7b4adfb965a4442c791c33"
  9.      },
  10.      "Payload": {
  11.          "blobData": {
  12.              "latitude": "",
  13.              "longitude": ""
  14.          },
  15.          "domain": "weather",
  16.          "intent": "GetGeneralMsgRequest"
  17.      }
  18.  }
  19.  
  20. 或者可以这样：也可以形成上面的数据
  21. json j2 = R"(
  22.  "Header": {
  23.          "DSN": "5ca439320d7b4adfb965a4442c791c33"
  24.      },
  25.      "Payload": {
  26.          "blobData": {
  27.              "latitude": "",
  28.              "longitude": ""
  29.          },
  30.          "domain": "weather",
  31.          "intent": "GetGeneralMsgRequest"
  32.      }
  33. )"_json;
  1. 要想打印上面封装的json的数据可以用以字符串的形式：
  2.  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：

  1. #include "rapidjson/document.h"
  2. #include "rapidjson/writer.h"
  3. #include "rapidjson/stringbuffer.h"
  4. #include <iostream>
  5. #include <string>
  6.  
  7. int main() {
  8.     const char* json = "{\"name\":\"John\",\"age\":30,\"city\":\"New York\"}";
  9.     rapidjson::Document doc;
  10.     doc.Parse(json);
  11.  
  12.     if (!doc.HasParseError()) {
  13.         std::string name = doc["name"].GetString();
  14.         int age = doc["age"].GetInt();
  15.         std::string city = doc["city"].GetString();
  16.  
  17.         std::cout << "Name: " << name << ", Age: " << age << ", City: " << city << std::endl;
  18.     } else {
  19.         std::cout << "JSON parse error" << std::endl;
  20.     }
  21.  
  22.     return 0;
  23. }

 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：

  1. #include <nlohmann/json.hpp>
  2. #include <iostream>
  3. #include <string>
  4.  
  5. int main() {
  6.     std::string json = "{\"name\":\"John\",\"age\":30,\"city\":\"New York\"}";
  7.     nlohmann::json j = nlohmann::json::parse(json);
  8.  
  9.     std::string name = j["name"];
  10.     int age = j["age"];
  11.     std::string city = j["city"];
  12.  
  13.     std::cout << "Name: " << name << ", Age: " << age << ", City: " << city << std::endl;
  14.  
  15.     return 0;
  16. }

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：

  1. {
  2.     "person": {
  3.         "name": "John",
  4.         "age": 30,
  5.         "address": {
  6.             "street": "123 Main St",
  7.             "city": "New York"
  8.         },
  9.         "hobbies": ["Reading", "Hiking"]
  10.     }
  11. }

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：

  1. #include "rapidjson/document.h"
  2. #include "rapidjson/writer.h"
  3. #include "rapidjson/stringbuffer.h"
  4. #include <iostream>
  5. #include <string>
  6.  
  7. int main() {
  8.     const char* json = "{\"person\":{\"name\":\"John\",\"age\":30,\"address\":{\"street\":\"123 Main St\",\"city\":\"New York\"},\"hobbies\":[\"Reading\",\"Hiking\"]}}";
  9.     rapidjson::Document doc;
  10.     doc.Parse(json);
  11.  
  12.     if (!doc.HasParseError()) {
  13.         const rapidjson::Value& person = doc["person"];
  14.         std::string name = person["name"].GetString();
  15.         int age = person["age"].GetInt();
  16.  
  17.         const rapidjson::Value& address = person["address"];
  18.         std::string street = address["street"].GetString();
  19.         std::string city = address["city"].GetString();
  20.  
  21.         const rapidjson::Value& hobbies = person["hobbies"];
  22.         if (hobbies.IsArray()) {
  23.             for (rapidjson::SizeType i = 0; i < hobbies.Size(); i++) {
  24.                 std::string hobby = hobbies[i].GetString();
  25.                 std::cout << "Hobby " << i + 1 << ": " << hobby << std::endl;
  26.             }
  27.         }
  28.  
  29.         std::cout << "Name: " << name << ", Age: " << age << std::endl;
  30.         std::cout << "Address: " << street << ", " << city << std::endl;
  31.     } else {
  32.         std::cout << "JSON parse error" << std::endl;
  33.     }
  34.  
  35.     return 0;
  36. }

使用nlohmann/json的示例代码：

  1. #include <nlohmann/json.hpp>
  2. #include <iostream>
  3. #include <string>
  4.  
  5. int main() {
  6.     std::string json = "{\"person\":{\"name\":\"John\",\"age\":30,\"address\":{\"street\":\"123 Main St\",\"city\":\"New York\"},\"hobbies\":[\"Reading\",\"Hiking\"]}}";
  7.     nlohmann::json j = nlohmann::json::parse(json);
  8.  
  9.     std::string name = j["person"]["name"];
  10.     int age = j["person"]["age"];
  11.  
  12.     std::string street = j["person"]["address"]["street"];
  13.     std::string city = j["person"]["address"]["city"];
  14.  
  15.     for (const auto& hobby : j["person"]["hobbies"]) {
  16.         std::string hobbyStr = hobby;
  17.         std::cout << "Hobby: " << hobbyStr << std::endl;
  18.     }
  19.  
  20.     std::cout << "Name: " << name << ", Age: " << age << std::endl;
  21.     std::cout << "Address: " << street << ", " << city << std::endl;
  22.  
  23.     return 0;
  24. }
  1. #include <nlohmann/json.hpp>
  2. #include <iostream>
  3. #include <string>
  4.  
  5. int main() {
  6.     std::string json = R"(
  7.     {
  8.         "Header": {
  9.             "sessionId": "1648612124933560_v20ZmHxNa4yx3",
  10.             "code": 200,
  11.             "message": "业务服务返回消息:StatusOK"
  12.         },
  13.         "Payload": {
  14.             "groupList": [
  15.                 {
  16.                     "groupName": "巅峰榜",
  17.                     "groupTopList": [
  18.                         {
  19.                             "listenNum": 18835312,
  20.                             "showTime": "2022-03-30",
  21.                             "songInfos": [
  22.                                 {
  23.                                     "singerId": 4658,
  24.                                     "singerMId": "000ZVS6E1f6f0d",
  25.                                     "singerName": "杨丞琳",
  26.                                     "songId": 648765,
  27.                                     "songMId": "004XNJ8Y2iD3VL",
  28.                                     "songName": "匿名的好友"
  29.                                 },
  30.                                 {
  31.                                     "singerId": 143,
  32.                                     "singerMId": "003Nz2So3XXYek",
  33.                                     "singerName": "陈奕迅",
  34.                                     "songId": 331839675,
  35.                                     "songMId": "003UkWuI0E8U0l",
  36.                                     "songName": "孤勇者"
  37.                                 }
  38.                             ],
  39.                             "topBannerPic": "http://y.gtimg.cn/music/photo_new/T003R500x500M000001namcx2Rs3fW.jpg",
  40.                             "topHeaderPic": "http://y.gtimg.cn/music/photo_new/T002R300x300M000000jcKFG0sQrD0.jpg",
  41.                             "topId": 62,
  42.                             "topName": "飙升榜",
  43.                             "totalNum": 100
  44.                         }
  45.                     ]
  46.                 }
  47.             ],
  48.             "msg": "OK",
  49.             "ret": 0,
  50.             "sessionId": "1648612124933560_v20ZmHxNa4yx3"
  51.         }
  52.     }
  53.     )";
  54.  
  55.     nlohmann::json j = nlohmann::json::parse(json);
  56.  
  57.     if (j.contains("Header") && j.contains("Payload")) {
  58.         const auto& header = j["Header"];
  59.         const auto& payload = j["Payload"];
  60.  
  61.         std::string sessionId = header["sessionId"];
  62.         int code = header["code"];
  63.         std::string message = header["message"];
  64.  
  65.         std::string msg = payload["msg"];
  66.         int ret = payload["ret"];
  67.         std::string payloadSessionId = payload["sessionId"];
  68.  
  69.         const auto& groupList = payload["groupList"];
  70.         if (groupList.is_array()) {
  71.             for (const auto& group : groupList) {
  72.                 std::string groupName = group["groupName"];
  73.                 const auto& groupTopList = group["groupTopList"];
  74.                 if (groupTopList.is_array()) {
  75.                     for (const auto& top : groupTopList) {
  76.                         int listenNum = top["listenNum"];
  77.                         std::string showTime = top["showTime"];
  78.                         int topId = top["topId"];
  79.                         std::string topName = top["topName"];
  80.                         int totalNum = top["totalNum"];
  81.                         
  82.                         const auto& songInfos = top["songInfos"];
  83.                         if (songInfos.is_array()) {
  84.                             for (const auto& songInfo : songInfos) {
  85.                                 int singerId = songInfo["singerId"];
  86.                                 std::string singerMId = songInfo["singerMId"];
  87.                                 std::string singerName = songInfo["singerName"];
  88.                                 int songId = songInfo["songId"];
  89.                                 std::string songMId = songInfo["songMId"];
  90.                                 std::string songName = songInfo["songName"];
  91.                                 
  92.                                 // 打印解析结果
  93.                                 std::cout << "Song Info:" << std::endl;
  94.                                 std::cout << "Singer ID: " << singerId << std::endl;
  95.                                 std::cout << "Singer MId: " << singerMId << std::endl;
  96.                                 std::cout << "Singer Name: " << singerName << std::endl;
  97.                                 std::cout << "Song ID: " << songId << std::endl;
  98.                                 std::cout << "Song MId: " << songMId << std::endl;
  99.                                 std::cout << "Song Name: " << songName << std::endl;
  100.                             }
  101.                         } else {
  102.                             std::cout << "songInfos is not an array" << std::endl;
  103.                         }
  104.                         
  105.                         // 打印解析结果
  106.                         std::cout << "Listen Num: " << listenNum << std::endl;
  107.                         std::cout << "Show Time: " << showTime << std::endl;
  108.                         std::cout << "Top ID: " << topId << std::endl;
  109.                         std::cout << "Top Name: " << topName << std::endl;
  110.                         std::cout << "Total Num: " << totalNum << std::endl;
  111.                     }
  112.                 } else {
  113.                     std::cout << "groupTopList is not an array" << std::endl;
  114.                 }
  115.  
  116.                 // 打印解析结果
  117.                 std::cout << "Group Name: " << groupName << std::endl;
  118.             }
  119.         } else {
  120.             std::cout << "groupList is not an array" << std::endl;
  121.         }
  122.     } else {
  123.         std::cout << "Header or Payload is not present in the JSON" << std::endl;
  124.     }
  125.  
  126.     return 0;
  127. }

 

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