Query a Device Shadow

Function

This API is used by an application to query the device shadow of a specific device, including the desired device properties (in the desired section) and the latest properties reported by the device (in the reported section).

Introduction:

A device shadow is a JSON file used to store and obtain device status.

Each device has only one device shadow, which is uniquely identified by the device ID.
A device shadow stores the properties (status) reported by a device and the properties (status) expected by an application.
You can obtain and set the device properties through the device shadow, regardless of whether the device is online.
After a device goes online or reports data, if the reported properties are different from the desired ones, the desired properties are delivered to the device. The desired properties can be delivered only when they have been defined in the product model and method is specified as W.

Restrictions:

Keys in the device shadow JSON file cannot contain periods (.), dollar signs ($), and the null character (hexadecimal ASCII code 00). Otherwise, the device shadow file cannot be updated.

Debugging

You can debug this API through automatic authentication in API Explorer or use the SDK sample code generated by API Explorer.

URI

GET /v5/iot/{project_id}/devices/{device_id}/shadow

**Table 1** Path Parameters
Parameter	Mandatory	Type	Description
project_id	Yes	String	Parameter description: project ID. For details about how to obtain the project ID, see Obtaining a Project ID.
device_id	Yes	String	Parameter description: device ID, which uniquely identifies a device. The value of this parameter is specified during device registration or allocated by the platform. Value: The value can contain a maximum of 128 characters. Only letters, digits, underscores (_), and hyphens (-) are allowed.

Request Parameters

**Table 2** Request header parameters
Parameter	Mandatory	Type	Description
X-Auth-Token	No	String	Parameter description: user token. You can obtain the token by calling the IAM API Obtaining a User Token Through Password Authentication. X-Subject-Token in the response header returned by the API is the desired user token. For details about how to obtain the token, see Token Authentication.
Instance-Id	No	String	Parameter description: instance ID. Unique identifier of each instance in the physical multi-tenant scenario. Mandatory for professional editions and recommended in other cases. Log in to the IoTDA console and choose Overview in the navigation pane to view the instance ID. For details, see Viewing Instance Details.

Response Parameters

Status code: 200

**Table 3** Response body parameters
Parameter	Type	Description
device_id	String	Device ID, used to uniquely identify a device. The value of this parameter is specified during device registration or allocated by the platform. If the value is allocated by the platform, the value is in the format of [product_id]_[node_id].
shadow	Array of DeviceShadowData objects	Device shadow data structure.

**Table 4** DeviceShadowData
Parameter	Type	Description
service_id	String	Device service ID, which is defined in the product model associated with the device.
desired	DeviceShadowProperties object	Latest desired properties delivered to the device. The data is JSON data and is in the format of key-value pairs. Each key is a parameter name of a property (property_name) in the product model.
reported	DeviceShadowProperties object	Latest properties reported by the device. The data is JSON data and is in the format of key-value pairs. Each key is a parameter name of a property (property_name) in the product model.
version	Long	Version of the device shadow. When this parameter is carried, the platform will check whether the value is the same as the current shadow version. The initial value is 0.

**Table 5** DeviceShadowProperties
Parameter	Type	Description
properties	Object	Properties stored in the device shadow. The data is JSON data and is in the format of key-value pairs. Each key is a parameter name of a property (property_name) in the product model. Only one-layer structure is supported, as shown in the example. Note: Keys in the JSON file cannot contain periods (.), dollar signs ($), and the null character (hexadecimal ASCII code 00). Keys that contain these special characters will cause device shadow update failures.
event_time	String	Time when the event occurred. The value is in the format of yyyyMMdd'T'HHmmss'Z', for example, 20151212T121212Z.

Example Requests

Query the device shadow of a specified device.

GET https://{endpoint}/v5/iot/{project_id}/devices/{device_id}/shadow

Example Responses

Status code: 200

{
  "device_id" : "40fe3542-f4cc-4b6a-98c3-61a49ba1acd4",
  "shadow" : [ {
    "service_id" : "WaterMeter",
    "desired" : {
      "properties" : {
        "temperature" : "60"
      },
      "event_time" : "20151212T121212Z"
    },
    "reported" : {
      "properties" : {
        "temperature" : "60"
      },
      "event_time" : "20151212T121212Z"
    },
    "version" : 1
  } ]
}