本文用代码简单介绍cjson的使用方法，1）创建json，从json中获取数据。2）创建json数组和解析json数组

1、创建json，从json中获取数据

  1 #include <stdio.h>                                                                                            
  2 #include "cJSON.h"
  3 
  4 char * makeJson()
  5 {
  6     cJSON * pJsonRoot = NULL;
  7 
  8     pJsonRoot = cJSON_CreateObject();
  9     if(NULL == pJsonRoot)
 10     {
 11         //error happend here
 12         return NULL;
 13     }
 14     cJSON_AddStringToObject(pJsonRoot,hello",0); line-height:1.5!important">hello world");
 15     cJSON_AddNumberToObject(pJsonRoot,0); line-height:1.5!important">number10010);
 16     cJSON_AddBoolToObject(pJsonRoot,0); line-height:1.5!important">bool1);
 17     cJSON * pSubJson = NULL;
 18     pSubJson = cJSON_CreateObject();
 19     if(NULL == pSubJson)
 20     {
 21          create object faild,exit
 22         cJSON_Delete(pJsonRoot);
 23          24     }
 25     cJSON_AddStringToObject(pSubJson,0); line-height:1.5!important">subjsonobja sub json string 26     cJSON_AddItemToObject(pJsonRoot,0); line-height:1.5!important">subobj",pSubJson);
 27 
 28     char * p = cJSON_Print(pJsonRoot);
 29    else use : 
 30      char * p = cJSON_PrintUnformatted(pJsonRoot);
 31     if(NULL == p)
 32     {
 33         convert json list to string faild,exit
 34         because sub json pSubJson han been add to pJsonRoot,so just delete pJsonRoot,if you also delete pSubJson,it will coredump,and error is : double free
 35         cJSON_Delete(pJsonRoot);
 36          37     }
 38     free(p);
 39     
 40     cJSON_Delete(pJsonRoot);
 41 
 42     return p;
 43 }
 44 
 45 void parseJson(char * pMsg)
 46 {
 47     if(NULL == pMsg)
 48     {
 49         return;
 50     }
 51     cJSON * pJson = cJSON_Parse(pMsg);
 52     if(NULL == pJson)                                                                                         
 53     {
 54          parse faild,return
 55       return ;
 56     }
 57 
 58      get string from json
 59     cJSON * pSub = cJSON_GetObjectItem(pJson,128); line-height:1.5!important"> 60     if(NULL == pSub)
 61     {
 62         get object named "hello" faild
 63     }
 64     printf(obj_1 : %s\nvaluestring);
 65 
 66      get number from json
 67     pSub = cJSON_GetObjectItem(pJson,128); line-height:1.5!important"> 68      69     {
 70         get number from json faild
 71     }
 72     printf(obj_2 : %d\nvalueint);
 73 
 74      get bool from json
 75     pSub = cJSON_GetObjectItem(pJson,128); line-height:1.5!important"> 76      77     {
 78          get bool from json faild
 79     }                                                                                                         
 80     printf(obj_3 : %d\n 81 
 82   get sub object
 83     pSub = cJSON_GetObjectItem(pJson,128); line-height:1.5!important"> 84      85     {
 86          get sub object faild
 87     }
 88     cJSON * pSubSub = cJSON_GetObjectItem(pSub,128); line-height:1.5!important"> 89     if(NULL == pSubSub)
 90     {
 91          get object from subject object faild
 92     }
 93     printf(sub_obj_1 : %s\nvaluestring);
 94 
 95     cJSON_Delete(pJson);
 96 }
 97 
 98 int main()
 99 {
100     char * p = makeJson();
101     102     {
103         return 0;
104     }
105     printf(%s\n106     parseJson(p);                                                                                             
107 　　free(p);　　//千万不要忘记释放内存呀，cJSON_Print()函数或者cJSON_PrintUnformatted（）产生的内存，使用free(char *)进行释放
108     109 }