1. 简介：

参考：

https://github.com/json-c/json-c/wiki

https://github.com/json-c/json-c

https://blog.csdn.net/u014530704/article/details/72674642?utm_source=copy

https://blog.csdn.net/w_ww_w/article/details/8295027

重点哈：https://blog.csdn.net/qimi123456/article/details/80426474

2. 编译运行：

json-c GitHub repo: https://github.com/json-c/json-c

$ git clone https://github.com/json-c/json-c.git

$ cd json-c

$ sh autogen.sh

followed by

$ ./configure # --enable-threading

$ make

$ make install

To build and run the test programs:

$ make check

$ make USE_VALGRIND=0 check # optionally skip using valgrind

3. 简单测试

1. 测试前，创建配置文件test.json，内容如下：

[root@localhost tests]# cat test.json

{"cmd":"SetPwd","params":{"id":111,"password":"test"}}

2. 编写测试文件test.c，内容如下：

#include #include #include #include #include "../json.h"

void main()

{

/*从文件中获取json对象*/

struct json_object * json_policy_array;

json_policy_array = json_object_from_file("./test.json");

printf("%s\n",json_object_to_json_string(json_policy_array));

/*从json对象中获取json对象*/

struct json_object * json_cmd ;

json_cmd = json_object_object_get(json_policy_array,"cmd");

printf("%s\n",json_object_to_json_string(json_cmd));

/*从json对象中获取json对象*/

struct json_object * json_params ;

json_params = json_object_object_get(json_policy_array,"params");

printf("%s\n",json_object_to_json_string(json_params));

int id = -1; //用于保存账号的值

int pwd_len = 0;

char *pwd = NULL; //用于保存密码的值

char *cmd = NULL; //用于保存cmd的值

/*从json对象中获取数据，首先获取对象，然后进行类型转换，转成int、float、string等*/

id = json_object_get_int(json_object_object_get(json_params,"id"));

printf("id = %d\n", id);

cmd = json_object_get_string(json_object_object_get(json_policy_array,"cmd"));

printf("cmd = %s\n", cmd);

pwd_len = json_object_get_string_len(json_object_object_get(json_params,"password"));

pwd = json_object_get_string(json_object_object_get(json_params,"password"));

printf("pwd_len = %d\n", pwd_len);

printf("pwd = %s\n", pwd);

/*向json文件中添加数据*/

//创建一个json对象newPobj

char *result = "OK";

//往json_policy_array里面添加键值对

json_object_object_add(json_policy_array,"result",json_object_new_string(result));

//创建一个json对象paramsProbj

json_object *paramsProbj = NULL;

paramsProbj = json_object_new_object();

//往paramsProbj里面添加键值对

json_object_object_add(paramsProbj,"id",json_object_new_int(200));

json_object_object_add(paramsProbj,"password",json_object_new_string("password2"));

//把paramsProbj添加到newPobj对象中

json_object_object_add(json_params,"paramsProbj",paramsProbj);

//这时还是将配置信息存在内存中呢

printf("%s\n",json_object_to_json_string(json_policy_array));

//将内存中修改后的配置文件，写会到磁盘中

json_object_to_file("./test.json",json_policy_array);

//释放内存

//引用计数方式，无需手动释放

}

3. 编译

[root@localhost tests]# gcc -ljson-c test.c

test.c: In function ‘main’:

test.c:32:6: warning: assignment discards ‘const’ qualifier from pointer target type [enabled by default]

cmd = json_object_get_string(json_object_object_get(json_policy_array,"cmd"));

^

test.c:36:6: warning: assignment discards ‘const’ qualifier from pointer target type [enabled by default]

pwd = json_object_get_string(json_object_object_get(json_params,"password"));

^

4.运行

[root@localhost tests]# ./a.out

{ "cmd": "SetPwd", "params": { "id": 111, "password": "test" } }

"SetPwd"

{ "id": 111, "password": "test" }

id = 111

cmd = SetPwd

pwd_len = 4

pwd = test

{ "cmd": "SetPwd", "params": { "id": 111, "password": "test", "paramsProbj": { "id": 200, "password": "password2" } }, "result": "OK" }

运行后，配置文件内容如下：

[root@localhost tests]# cat test.json

{"cmd":"SetPwd","params":{"id":111,"password":"test","paramsProbj":{"id":200,"password":"password2"}},"result":"OK"}

4. 项目应用

在项目中，可以对此开源库进行封装，以使用项目本身；

为了是运行中的进程能够在配置文件改变后重新读取，需要引入信号机制：

1. 可以直接在信号处理函数中重新读取配置文件；

2. 也可以使用单独的线程，线程阻塞等待信号量，信号处理函数中释放信号量，线程获得信号量后，读写配置文件。