cJSON解析json文件

拷備.c和.h文件到指定的目錄中

構建需要使用的函數

extern cJSON *cJSON_CreateObject(void);
extern void cJSON_AddItemToObject(cJSON *object,const char *string,cJSON *item);
 
extern cJSON *cJSON_CreateNull(void);
extern cJSON *cJSON_CreateTrue(void);
extern cJSON *cJSON_CreateFalse(void);
extern cJSON *cJSON_CreateBool(int b);
extern cJSON *cJSON_CreateNumber(double num);
extern cJSON *cJSON_CreateString(const char *string);
extern cJSON *cJSON_CreateArray(void);
extern cJSON *cJSON_CreateObject(void);

  #include <stdio.h>
  #include <unistd.h>
  #include <stdlib.h>
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <string.h>
 #include "cJSON.h"                                                                                                                  
  
 int main(int argc, char *argv[])                                                         
  {
             
      // 創建對象
     cJSON* obj = cJSON_CreateObject();
      // 創建子對象
     cJSON* subObj = cJSON_CreateObject();
      // 添加key-value
    cJSON_AddItemToObject(subObj,"factory",cJSON_CreateString("一汽大眾"));
    cJSON_AddItemToObject(subObj,"last",cJSON_CreateNumber(31));
     cJSON_AddItemToObject(subObj,"price",cJSON_CreateNumber(83));
     cJSON_AddItemToObject(subObj,"sell",cJSON_CreateNumber(49));
     cJSON_AddItemToObject(subObj,"sum",cJSON_CreateNumber(80));
      // 創建數組
     cJSON* array = cJSON_CreateArray();
     cJSON_AddItemToArray(array,cJSON_CreateNumber(123));
     cJSON_AddItemToArray(array,cJSON_CreateNumber(1));
     cJSON_AddItemToArray(array,cJSON_CreateString("hello,world"));
      // 創建對象
     cJSON* childObj = cJSON_CreateObject();
     cJSON_AddItemToObject(childObj,"梅塞奔馳",cJSON_CreateString("心所向，持以恆"));
      cJSON_AddItemToArray(array,childObj);
      cJSON_AddItemToObject(subObj,"othre",array);
  
      // obj中添加key - value
      cJSON_AddItemToObject(obj,"奔馳",subObj);
  
      // 數據格式化
      char* data = cJSON_Print(obj);
      FILE* fp = fopen("car.json","w");
      fwrite(data,sizeof(char),strlen(data)+1,fp);
      fclose(fp);
      
          return 0;
  }

gcc *.c -o app -lm -I./include

{
        "奔馳": {
                "factory":      "一汽大眾",
                "last": 31,
                "price": 83,
                "sell": 49,
                "sum":  80,
                "othre":        [123, 1, "hello,world", {
                                "梅塞奔馳":     "心所向，持以恆"
                        }]
        }
}

解析需要的函數

/* Supply a block of JSON, and this returns a cJSON object you can interrogate. Call cJSON_Delete when finished. */
extern cJSON *cJSON_Parse(const char *value);//從 給定的json字符串中得到cjson對象
/* Render a cJSON entity to text for transfer/storage. Free the char* when finished. */
extern char  *cJSON_Print(cJSON *item);//從cjson對象中獲取有格式的json對象
/* Render a cJSON entity to text for transfer/storage without any formatting. Free the char* when finished. */
extern char  *cJSON_PrintUnformatted(cJSON *item);//從cjson對象中獲取無格式的json對象
 
/* Delete a cJSON entity and all subentities. */
extern void   cJSON_Delete(cJSON *c);//刪除cjson對象，釋放鏈表占用的內存空間
 
/* Returns the number of items in an array (or object). */
extern int    cJSON_GetArraySize(cJSON *array);//獲取cjson對象數組成員的個數
/* Retrieve item number "item" from array "array". Returns NULL if unsuccessful. */
extern cJSON *cJSON_GetArrayItem(cJSON *array,int item);//根據下標獲取cjosn對象數組中的對象
/* Get item "string" from object. Case insensitive. */
extern cJSON *cJSON_GetObjectItem(cJSON *object,const char *string);//根據鍵獲取對應的值（cjson對象）
 
/* For analysing failed parses. This returns a pointer to the parse error. You'll probably need to look a few chars back to make sense of it. Defined when cJSON_Parse() returns 0. 0 when cJSON_Parse() succeeds. */
extern const char *cJSON_GetErrorPtr(void);//獲取錯誤字符串

代碼示例

#include <stdio.h>                                                                                       
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include "cJSON.h"

int main(int argc, char *argv[])
{
    if(argc < 2)
    {
        printf("./app jsonfile\n");
        exit(1);
    }
    // 加載json文件
    FILE* fp = fopen(argv[1],"r");
    char buf[1024] = {0};
    fread(buf,1,sizeof(buf),fp);
    cJSON* root = cJSON_Parse(buf);
    cJSON* subobj = cJSON_GetObjectItem(root,"奔馳");
    // 判斷對象是否存在
    if(subobj)
    {
        printf("奔馳: \n");
        // 獲取子對象
        cJSON* item = NULL;
        item= cJSON_GetObjectItem(subobj,"factory");
        printf("%s: %s \n",item->string,item->valuestring);
        item= cJSON_GetObjectItem(subobj,"last");
        printf("last: %d \n",item->valueint);
        item= cJSON_GetObjectItem(subobj,"price");
        printf("price: %d\n",item->valueint);
        item= cJSON_GetObjectItem(subobj,"sell");
        printf("sell: %d\n",item->valueint);
        item= cJSON_GetObjectItem(subobj,"sum");
        printf("sum: %d\n",item->valueint);
        cJSON *other = NULL;
        other = cJSON_GetObjectItem(subobj,"othre");
        //        if(cJSON_IsArray(other))
        printf("other: \n");
        if(cJSON_Array == other->type)
        {   
            for(int i = 0;i<cJSON_GetArraySize(other);++i)
            {   
                item = cJSON_GetArrayItem(other,i);
                if(cJSON_IsNumber(item))
                    printf("  %d \n",item->valueint);
                else if(cJSON_IsString(item))
                    //else if(cJSON_IsObject(item))
                {   
                    cJSON* temp = cJSON_GetArrayItem(other,i);
                    printf(" %s \n",temp->valuestring);
                }   
                else if(cJSON_Object == item->type)
                {   
                    cJSON* temp = cJSON_GetObjectItem(item,"梅塞奔馳");
                    printf("%s %s\n",temp->string,temp->valuestring);
                }   
            }   
        }   
    }   
    cJSON_Delete(root);
    fclose(fp);
    return 0;
}