【Linux C编程】第二十章XML-JSON之示例

（3）示例

    生成下面的JSON

car.json

1 {
 2     "奔驰":    {
 3         "factory":    "一汽大众",
 4         "last":    31,
 5         "price":    83,
 6         "sell":    49,
 7         "sum":    80,
 8         "other":    [124, "hello, world", false]
 9     }
10 }

create_car.c

1 #include <stdio.h>
 2 #include <string.h>
 3 #include "cJSON.h"
 4 
 5 int main(int argc, const char* argv[])
 6 {
 7     // 创建json对象
 8     cJSON* obj = cJSON_CreateObject(); 
 9 
10     // 创建子对象 - 品牌
11     cJSON* brand = cJSON_CreateObject();
12     // 添加键值对
13     cJSON_AddItemToObject(brand, "factory", cJSON_CreateString("一汽大众"));
14     cJSON_AddItemToObject(brand, "last", cJSON_CreateNumber(31));
15     cJSON_AddItemToObject(brand, "price", cJSON_CreateNumber(83));
16     cJSON_AddItemToObject(brand, "sell", cJSON_CreateNumber(49));
17     cJSON_AddItemToObject(brand, "sum", cJSON_CreateNumber(80));
18 
19     // 创建json数组
20     cJSON* array = cJSON_CreateArray();
21     cJSON_AddItemToArray(array, cJSON_CreateNumber(124));
22     cJSON_AddItemToArray(array, cJSON_CreateString("hello, world"));
23     cJSON_AddItemToArray(array, cJSON_CreateBool(0));
24     cJSON_AddItemToObject(brand, "other", array);
25 
26     cJSON_AddItemToObject(obj, "奔驰", brand);
27 
28     // 格式化json对象
29     char* text = cJSON_Print(obj);
30     FILE* fp = fopen("car.json", "w");
31     fwrite(text, 1, strlen(text), fp);
32     fclose(fp);
33 
34     return 0;
35 }

源码：

cJSON.c

cJSON.h

parsejson.c

1 #include <stdio.h>
 2 #include <string.h>
 3 #include "cJSON.h"
 4 
 5 int main(int argc, const char* argv[])
 6 {
 7     if(argc < 2)
 8     {
 9         printf("./a.out jsonfile\n");
10         return 0;
11     }
12 
13     // 加载json文件 
14     FILE* fp = fopen(argv[1], "r");
15     char buf[1024] = {0};
16     fread(buf, 1, sizeof(buf), fp);
17     cJSON* root = cJSON_Parse(buf);
18 
19     cJSON* subobj = cJSON_GetObjectItem(root, "奔驰");
20     // 判断对象是否存在
21     if( subobj )
22     {
23         // 获取子对象
24         cJSON* factory = cJSON_GetObjectItem(subobj, "factory");
25         cJSON* last = cJSON_GetObjectItem(subobj, "last");
26         cJSON* price = cJSON_GetObjectItem(subobj, "price");
27         cJSON* sell = cJSON_GetObjectItem(subobj, "sell");
28         cJSON* sum = cJSON_GetObjectItem(subobj, "sum");
29         cJSON* other = cJSON_GetObjectItem(subobj, "other");
30 
31         // 打印value值
32         printf("奔驰：\n");
33         printf("    factory: %s\n", cJSON_Print(factory));
34         printf("    last: %s\n", cJSON_Print(last));
35         printf("    price: %s\n", cJSON_Print(price));
36         printf("    sell: %s\n", cJSON_Print(sell));
37         printf("    sum: %s\n", cJSON_Print(sum));
38 
39         // 打印数组内容
40         printf("    other:\n");
41         if(other->type == cJSON_Array)
42         {
43             for(int i=0; i<cJSON_GetArraySize(other); ++i)
44             {
45                 cJSON* node = cJSON_GetArrayItem(other, i);
46                 // 判断数据类型
47                 if(node->type == cJSON_String)
48                 {
49                     printf("        %s  \n", node->valuestring);
50                 }
51                 if(node->type == cJSON_Number)
52                 {
53                     printf("        %d\n", node->valueint);
54                 }
55                 if(node->type == cJSON_True)
56                 {
57                     printf("        %d\n", node->valueint);
58                 }
59                 if(node->type == cJSON_False)
60                 {
61                     printf("        %d\n", node->valueint);
62                 }
63             }
64         }
65     }
66 
67     cJSON_Delete(root);
68     fclose(fp);
69 
70 
71     return 0;
72 }

注意：上面的cJSON.c和cJSON.h是 cJSON-master.zip包里面的。

cJSON结构体：

#define cJSON_Invalid              (0)
#define cJSON_False                  (1 << 0)
#define cJSON_True                  (1 << 1)
#define cJSON_NULL                (1 << 2)
#define cJSON_Number           (1 << 3)
#define cJSON_String                (1 << 4)
#define cJSON_Array                (1 << 5)
#define cJSON_Object              (1 << 6)
#define cJSON_Raw                  (1 << 7) 

/* The cJSON structure: */
typedef struct cJSON
{
    struct cJSON *next;
    struct cJSON *prev;
    struct cJSON *child;

    int type;
    char *valuestring;
    int valueint;                                                                                                                         
    double valuedouble;

    char *string;
} cJSON;