IoT Hub message routing query syntax

Question

Hello,

I have a 2D array as shown below in the message body received by IoT Hub.I have been trying various options in message routing query to check for the existence of the key "dioData" but nothing has worked so far.Pls suggest on how to check for the existence of the key "dioData" using message routing query.

Thanks

{

 "dioData": [

            [

                1,

                1540,

                55597

            ],

            [

                0,

                1483,

                18203

            ]

        ]

    }

Answer 1

Hi @Arun Kumar Greetings! Welcome to Microsoft Q&A forum. Thank you for posting this question here.

The IoTHub routing query syntax, although, is a SQL like language, offers limited set of functions and operations. To find the list of supported functions offered by IoTHub Query language, please refer to the section Functions of the article IoT Hub query language for device and module twins, jobs, and message routing

Coming to your use case, since you are trying to validate a 2D dimensional array, you can leverage IS_ARRAY function to determine of the property dioData is of the expected format.

For example, if the dioData is of the below format, the routing query IS_ARRAY($body.dioData) finds a match

{
	"dioData" : [[1,1540,55597],[0.1483,18203]]
}

Please note that the above query also matches an empty array such as {"dioData" : []}

If you are certain that your property is a 2X3 matric, you can even enhance the routing query by testing the first row of the property. Here is the routing query syntax IS_ARRAY($body.dioData[0]). This checks if the first entry of the property is an array.

For the IoTHub message routing to work, kindly ensure that the message should be in a JSON format and encoded in either UTF-8, UTF-16 or UTF-32. The contentType system property must be application/JSON.

Here is a sample code in Python showing how I have formulated the data

dio_data = [
    [1, 1540, 55597],
    [0, 1483, 18203]
]
message_dict = {
    "dioData": dio_data
}
message_json = json.dumps(message_dict)
message = Message(message_json, content_encoding="utf-8", content_type="application/json")
client.send_message(message)

I have the routed query set to check the array validity of the first entry of the property as follows

I could see the message routed to the configured endpoint as expected.

Hope this helps! If you need to perform more validations on the property, I appreciate it if you can share more details on your use case to help us provide more appropriate feedback.

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