cJSON 入门与应用
1. cJSON简介
cJSON aims to be the dumbest possible parser that you can get your job done with. It's a single file of C, and a single header file.
JSON is described best here: http://www.json.org/ It's like XML, but fat-free. You use it to move data around, store things, or just generally represent your program's state.
cJSON 下载地址：https://github.com/DaveGamble/cJSON
2. cJSON常用函数简介
cJSON * cJSON_CreateObject();
创建一个json对象，返回一个cJSON结构体类型的指针。
cJSON *cJSON_CreateArray();
创建一个数组对象，返回一个cJSON结构体类型的指针。
cJSON *cJSON_CreateString(const char *string);
创建一个字符串对象，传入一个char *类型的字符串，返回一个cJSON结构体类型的指针。
void cJSON_AddItemToArray(cJSON *array, cJSON *item);
向数组对象中添加一个元素，传入参数array为cJSON *结构体类型的指针，为数组对象; item为添加入数字对象中的对象指针。
void
cJSON_AddItemToObject(cJSON *object,const char *string,cJSON *item);
向json对象中添加一对元素，object为json对象，string为加入一对元素中的name，item为加入一对元素中的value。
cJSON *cJSON_Parse(const char *value);
解析一个json串，传入一个json格式的字符串，返回一个cJSON *类型的结构体指针。
char *cJSON_Print(cJSON *item);
将一个cJSON结构体代表的json对象转换为一个json格式的字符串。
void cJSON_Delete(cJSON *c);
释放一个cJSON对象所占用的内存空间。
3. 应用
以此json串为例进行json的生成和解析：
{
"name": "中国",
"province": [{
"name": "黑龙江",
"cities": {
"city": ["哈尔滨", "大庆"]
}
}, {
"name": "广东",
"cities": {
"city": ["广州", "深圳", "珠海"]
}
}, {
"name": "台湾",
"cities": {
"city": ["台北", "高雄"]
}
}, {
"name": "新疆",
"cities": {
"city": ["乌鲁木齐"]
}
}]
}
3.1 生成json
#include <stdio.h>
#include "cJSON.h"
#include "cJSON_Utils.h"
#pragma comment(lib,"cjson.lib")
int main(void)
{
cJSON * json = cJSON_CreateObject();
cJSON *provinceArray = cJSON_CreateArray();
cJSON *heilongjiang = cJSON_CreateObject();
cJSON *hljcities = cJSON_CreateObject();
cJSON *hljcityArray = cJSON_CreateArray();
cJSON *guangdong = cJSON_CreateObject();
cJSON *gdcities = cJSON_CreateObject();
cJSON *gdcityArray = cJSON_CreateArray();
cJSON *taiwan = cJSON_CreateObject();
cJSON *twcities = cJSON_CreateObject();
cJSON *twcityArray = cJSON_CreateArray();
cJSON *xinjiang = cJSON_CreateObject();
cJSON *xjcities = cJSON_CreateObject();
cJSON *xjcityArray = cJSON_CreateArray();
cJSON_AddStringToObject(json, "name", "中国");
cJSON_AddStringToObject(heilongjiang, "name", "黑龙江");
cJSON_AddItemToArray(hljcityArray, cJSON_CreateString("哈尔滨"));
cJSON_AddItemToArray(hljcityArray, cJSON_CreateString("大庆"));
cJSON_AddItemToObject(hljcities, "city", hljcityArray);
cJSON_AddItemToObject(heilongjiang, "cities", hljcities);
cJSON_AddStringToObject(guangdong, "name", "广东");
cJSON_AddItemToArray(gdcityArray, cJSON_CreateString("广州"));
cJSON_AddItemToArray(gdcityArray, cJSON_CreateString("深圳"));
cJSON_AddItemToArray(gdcityArray, cJSON_CreateString("珠海"));
cJSON_AddItemToObject(gdcities, "city", gdcityArray);
cJSON_AddItemToObject(guangdong, "cities", gdcities);
cJSON_AddStringToObject(taiwan, "name", "台湾");
cJSON_AddItemToArray(twcityArray, cJSON_CreateString("台北"));
cJSON_AddItemToArray(twcityArray, cJSON_CreateString("高雄"));
cJSON_AddItemToObject(twcities, "city", twcityArray);
cJSON_AddItemToObject(taiwan, "cities", twcities);
cJSON_AddStringToObject(xinjiang, "name", "新疆");
cJSON_AddItemToArray(xjcityArray, cJSON_CreateString("乌鲁木齐"));
cJSON_AddItemToObject(xjcities, "city", xjcityArray);
cJSON_AddItemToObject(xinjiang, "cities", xjcities);
cJSON_AddItemToArray(provinceArray, heilongjiang);
cJSON_AddItemToArray(provinceArray, guangdong);
cJSON_AddItemToArray(provinceArray, taiwan);
cJSON_AddItemToArray(provinceArray, xinjiang);
cJSON_AddItemToObject(json, "province", provinceArray);
printf("%s\n", cJSON_Print(json));
if ( NULL != json )
{
cJSON_Delete(json);
json = NULL;
}
return 0;
}
3.2 解析json
#include <stdio.h>
#include "cJSON.h"
#include "cJSON_Utils.h"
#pragma comment(lib,"cjson.lib")
int main(void)
{
const char *jsonStr = "{ \
\"name\": \"中国\", \
\"province\": [{ \
\"name\": \"黑龙江\", \
\"cities\": { \
\"city\": [\"哈尔滨\", \"大庆\"] \
} \
}, { \
\"name\": \"广东\", \
\"cities\": { \
\"city\": [\"广州\", \"深圳\", \"珠海\"] \
} \
}, { \
\"name\": \"台湾\", \
\"cities\": { \
\"city\": [\"台北\", \"高雄\"] \
} \
}, { \
\"name\": \"新疆\", \
\"cities\": { \
\"city\": [\"乌鲁木齐\"] \
} \
}] \
}";
cJSON *json = cJSON_Parse(jsonStr);
if ( NULL != json )
{
cJSON * temp = cJSON_GetObjectItem(json, "name");
if ( NULL != temp )
printf( "name : %s\n", temp->valuestring);
temp = cJSON_GetObjectItem(json, "province");
printf( "province : \n");
if ( NULL != temp )
{
int i = 0;
int icount = cJSON_GetArraySize(temp);
for (; i < icount; ++i)
{
cJSON * province = cJSON_GetArrayItem(temp, i);
if ( NULL != province)
{
cJSON * name = NULL;
cJSON * cities = NULL;
name = cJSON_GetObjectItem(province, "name");
cities = cJSON_GetObjectItem(province, "cities");
if ( NULL != name )
printf(" name : %s\n", name->valuestring);
printf(" cities : \n");
if ( NULL != cities )
{
cJSON * city = cJSON_GetObjectItem(cities, "city");
printf (" city:");
if ( NULL != city )
{
int j = 0;
int jcount = cJSON_GetArraySize(city);
for (; j < jcount; ++j)
{
cJSON *cityItem = cJSON_GetArrayItem(city, j);
if ( NULL != cityItem )
printf ("%s ", cityItem->valuestring);
}
}
printf ("\n\n");
}
}
}
}
cJSON_Delete(json);
json = NULL;
}
return 0;
}
