c - azure-iot-sdk-c 反序列化 JSON 负载

Question

我正在使用 IoT_Hub Device Method samples 开始使用 Azure IoT SDK C 库.

有谁知道SDK是否提供反序列化JSON消息负载的功能？有一些不错examples用于将负载序列化为 JSON，但我找不到对应的。

我很确定 SDK 具有一些用于 JSON 反序列化的功能，例如像这样的东西:

BEGIN_NAMESPACE(WeatherStation);

DECLARE_MODEL(ContosoAnemometer, 
  WITH_DATA(ascii_char_ptr, DeviceId), 
  WITH_DATA(int, WindSpeed), 
  WITH_DATA(float, Temperature), 
  WITH_DATA(float, Humidity), 
  WITH_ACTION(TurnFanOn)
); 

END_NAMESPACE(WeatherStation);


static int DeviceMethodCallback(const char* method_name, const unsigned char* payload, ...) 
{ 
    (void)userContextCallback; 

    ContosoAnemometer* myWeather = CREATE_MODEL_INSTANCE(WeatherStation, ContosoAnemometer);
    DESERIALIZE(myWeather, payload)

    printf("Device Id: %i\r\n", myWeather->DeviceId);

    // etc. etc.
}

Answer 1

在Azure IoT SDK for C中，它使用serializer库来序列化消息发送，但没有用于接收消息的couterpart(DESERIALIZE)。请参阅 more about serializer .在serializer组件中，你会发现jsondecoder.c，它定义了一些解码json数据的方法。

还有更多，您会发现 parson成分。可以用来反序列化json字符串中的对象，可以引用下面的代码。

jsonstr

{"desString":"P7svG%2BLoUZEbB8Le5jP1%2BpuX2OVWLE4xWMzFcYFCRvNvDlcFVm%2B8z2VFO%2F%2BaEB8UAMa%2FZ0GGhooGNMWFE98Zmw%3D%3D","caller":{"mobile":"13996130361"},"accountId":"b5091dc91d700c6bf714e5fc446797d3","tmpTime":1428545890,"otherParam":"{id:12}","participant":[{"mobile":"18623582801"}],"servletUrl":"http://192.168.1.1:8090/xdr"}

C 代码

JSON_Value *root_value=NULL;
root_value = json_parse_string(jsonstr);
JSON_Object *root_object;
if(json_value_get_type(root_value) == JSONObject)
{
    root_object = json_value_get_object(root_value);
    const char *desString = json_object_get_string(root_object, "desString");
    if(desString!=NULL)strncpy(pPost->desString,desString,LENGTH128-1);
    const char *accountId = json_object_get_string(root_object, "accountId");
    if(accountId!=NULL)strncpy(pPost->accountId,accountId,LENGTH32);
    double tmpTime = json_object_get_number(root_object, "tmpTime");
    const char *caller = json_object_dotget_string(root_object,"caller.mobile");
    if(caller!=NULL)strncpy(pPost->caller,caller,LENGTH16-1);
    const char *servletUrl = json_object_dotget_string(root_object,"servletUrl");
    if(servletUrl!=NULL)strncpy(pPost->servletUrl,servletUrl,LENGTH128-1);
    const char *otherParam = json_object_dotget_string(root_object,"otherParam");
    if(otherParam!=NULL)strncpy(pPost->otherParam,otherParam,LENGTH128-1);

    JSON_Array *array;
    array = json_object_get_array(root_object, "participant");
    int i =0;
    for(i;i<json_array_get_count(array);i++)
    {
        JSON_Object *tmp = json_array_get_object(array,i);
        if(tmp!=NULL)
        {
            const char *mobile = json_object_get_string(tmp,"mobile");
            if(mobile!=NULL)strncpy(pPost->callee,mobile,LENGTH16-1);
        }
    }
}
if(root_value)json_value_free(root_value);