cJSON使用

c语言源码下载地址：https://github.com/DaveGamble/cJSON

其他语言源码下载地址：http://www.json.org/

用 cJSON_PrintUnformatted(root) 或者 cJSON_Print(root);来将json对象转换成普通的字符串，并且都是以该json对象的根为基点。两个API的区别即是：一个是没有格式的：也就是转换出的字符串中间不会有" " " "之类的东西存在，而cJSON_Print(root);打印出来是人看起来很舒服的格式。仅此而已。

 

 

cJSON的使用

JSON格式的生产 

以下代码不需要执行cJSON_Delete(sub_js)，因为删除父CJSON对象时，会删除子CJSON对象

    cJSON *root=NULL;
    cJSON *sub_js=NULL;
    char *out=NULL;
    
    root = cJSON_CreateObject();
    cJSON_AddStringToObject(root, "ver", "v1.0.0");
    cJSON_AddStringToObject(root, "did", "066EFF3638324D4D43183319");
    cJSON_AddStringToObject(root, "hardware_ver", "V1.0.0");
    cJSON_AddStringToObject(root, "software_ver", "V1.0.0");
    cJSON_AddItemToObject(root, "data", sub_js = cJSON_CreateObject());
    cJSON_AddNumberToObject(sub_js, "status", 1);
    cJSON_AddTrueToObject(sub_js, "material");
    cJSON_AddTrueToObject(sub_js, "power_on");
    cJSON_AddNumberToObject(sub_js, "qty", 123);
    cJSON_AddStringToObject(root, "dt", "2017-11-04T05:15:52");
    
    out=cJSON_Print(root);
    cJSON_Delete(root);    
    debug("%s
",out);    
    free(out);

打印出

{
    "ver":    "v1.0.0",
    "did":    "066EFF3638324D4D43183319",
    "hardware_ver":    "V1.0.0",
    "software_ver":    "V1.0.0",
    "data":    {
        "status":    1,
        "material":    true,
        "power_on":    true,
        "qty":    123
    },
    "dt":    "2017-11-04T05:15:52"
}

解析JSON格式（读取JSON格式数据，只要是在同一个{}内，不需要从上往下按顺序读，支持乱序）

{
    "wifi":    {
        "ssid":    "hello World",
        "pwd":    "234sdlfkj23"
    },
    "mqtt":    {
        "server":    "192.168.31.240",
        "port":    1883,
        "clientid":    "asdfghjklzxcvbnm",
        "username":    "1234567asdfghj",
        "password":    "asdfghjkerty"
    },
    "option":    {
        "working_signal_last_time":    15,
        "material_empty_signal_last_time":    6,
        "material_full_signal_last_time":    3,
        "status_send_time":    30
    }
}

 UART_RxBuf_tmp就是上面的JSON格式数据

            char *out;
            cJSON *json, *item1, *item2;
            
            json=cJSON_Parse((char const *)UART_RxBuf_tmp);
            if (!json) 
            {
                debug("Error before:%s
",cJSON_GetErrorPtr());
            }
            else
            {
                item1 = cJSON_GetObjectItem(json, "wifi");
                item2 = cJSON_GetObjectItem(item1, "ssid");
                debug("%s: %s", item2->string, item2->valuestring);
                item2 = cJSON_GetObjectItem(item1, "pwd");
                debug("%s: %s", item2->string, item2->valuestring);
                debug("%s",wifi_information);
                item1 = cJSON_GetObjectItem(json, "mqtt");
                item2 = cJSON_GetObjectItem(item1, "server");
                debug("%s: %s", item2->string, item2->valuestring);
                item2 = cJSON_GetObjectItem(item1, "port");
                debug("%s: %d", item2->string, item2->valueint);
                debug("%s",server_information);
                item2 = cJSON_GetObjectItem(item1, "clientid");
                debug("%s: %s", item2->string, item2->valuestring);
                item2 = cJSON_GetObjectItem(item1, "username");
                debug("%s: %s", item2->string, item2->valuestring);
                item2 = cJSON_GetObjectItem(item1, "password");
                debug("%s: %s", item2->string, item2->valuestring);
                item1 = cJSON_GetObjectItem(json, "option");
                item2 = cJSON_GetObjectItem(item1, "working_signal_last_time");
                debug("%s: %d", item2->string, item2->valueint);
                item2 = cJSON_GetObjectItem(item1, "material_empty_signal_last_time");
                debug("%s: %d", item2->string, item2->valueint);
                item2 = cJSON_GetObjectItem(item1, "material_full_signal_last_time");
                debug("%s: %d", item2->string, item2->valueint);
                item2 = cJSON_GetObjectItem(item1, "status_send_time");
                debug("%s: %d", item2->string, item2->valueint);
                
                out=cJSON_Print(json);
                cJSON_Delete(json);
                debug("%s
",out);
                free(out);
            }

创建带数组的JSON

    cJSON *root=NULL;
    cJSON *sub_js=NULL;
    char *out=NULL;
    
    root = cJSON_CreateObject();
    cJSON_AddStringToObject(root, "ver", protocol_ver);
    cJSON_AddStringToObject(root, "did", (char const*)g_MCU_uniqueID_str);
    cJSON_AddStringToObject(root, "hardware_ver", hardware_ver);
    cJSON_AddStringToObject(root, "software_ver", software_ver);
    cJSON_AddItemToObject(root, "data", sub_js = cJSON_CreateObject());
    
    cJSON *array;
    array = cJSON_CreateArray();
    cJSON_AddItemToObject(sub_js, "M", array);
    cJSON_AddItemToArray(array, cJSON_CreateBool(1));
    cJSON_AddItemToArray(array, cJSON_CreateBool(1));
    cJSON_AddItemToArray(array, cJSON_CreateBool(1));
    cJSON_AddItemToArray(array, cJSON_CreateBool(0));
    cJSON_AddItemToArray(array, cJSON_CreateBool(0));
    array = cJSON_CreateArray();
    cJSON_AddItemToObject(sub_js, "D", array);
    cJSON_AddItemToArray(array, cJSON_CreateNumber(12312));
    cJSON_AddItemToArray(array, cJSON_CreateNumber(12334));
    cJSON_AddItemToArray(array, cJSON_CreateNumber(967425));
    
    char time[20];
    get_formatted_time(time);
    cJSON_AddStringToObject(root, "dt", (char const*)time);
    
    out=cJSON_Print(root);
    cJSON_Delete(root);
    debug("%s
",out);
    MQTT_publish(out, "init");
    vPortFree(out);