I am implementing a IoT Edge App, and I want to set/get the value of ModuleTwin and monitor the value change of ModuleTwin. I refer to the sample: https://github.com/Azure/azure-iot-sdk-java/blob/master/device/iot-device-samples/module-twin-sample/src/main/java/samples/com/microsoft/azure/sdk/iot/ModuleTwinSample.java My understanding is following: set ModuleTwin: ModuleClient.sendReportedProperties() get ModuleTwin: ModuleClient.getTwin() monitor ModuleTwin: ModuleClient.subscribeToTwinDesiredProperties() Am I right? I try to test with iotedgehubdev, but after excute client.getTwin(), there is no callback excuted. Output logs: MyFirstModule | Client created MyFirstModule | Open connection to IoT Hub. MyFirstModule | Connection Status: Connected MyFirstModule | Start device Twin and get remaining properties... MyFirstModule | IoT Hub responded to device twin operation with status OK MyFirstModule | Subscribe to Desired properties on device Twin... MyFirstModule | Get device Twin... What's the problem?

We can use the following APIs: Get Module Twin: ModuleClient. startTwin (IotHubEventCallback deviceTwinStatusCallback, Object deviceTwinStatusCallbackContext, DeviceTwin. TwinPropertyCallBack genericPropertyCallBack, Object genericPropertyCallBackContext) Set Module Twin: InternalClient. sendReportedProperties (Set<DeviceTwin.Property> reportedProperties) Monitor Module Twin: InternalClient.subscribeToTwinDesiredProperties(Map<DeviceTwin.Property,DeviceTwin.Pair<DeviceTwin.TwinPropertyCallBack,Object>> onDesiredPropertyChange) For details we can refer to sample: https://github.com/Azure/azure-iot-sdk-java/blob/master/device/iot-device-samples/module-twin-sample/src/main/java/samples/com/microsoft/azure/sdk/iot/ModuleTwinSample.java

[Azure IoT SDK]How can I set/get/monitor the value of ModuleTwin?

罗宇恒罗宇恒 571

I am implementing a IoT Edge App, and I want to set/get the value of ModuleTwin and monitor the value change of ModuleTwin.

I refer to the sample:
https://github.com/Azure/azure-iot-sdk-java/blob/master/device/iot-device-samples/module-twin-sample/src/main/java/samples/com/microsoft/azure/sdk/iot/ModuleTwinSample.java

My understanding is following:

set ModuleTwin: ModuleClient.sendReportedProperties()
get ModuleTwin: ModuleClient.getTwin()
monitor ModuleTwin: ModuleClient.subscribeToTwinDesiredProperties()
Am I right?

I try to test with iotedgehubdev, but after excute client.getTwin(), there is no callback excuted.

Output logs:

MyFirstModule    | Client created
MyFirstModule    | Open connection to IoT Hub.
MyFirstModule    | Connection Status: Connected
MyFirstModule    | Start device Twin and get remaining properties...
MyFirstModule    | IoT Hub responded to device twin operation with status OK
MyFirstModule    | Subscribe to Desired properties on device Twin...
MyFirstModule    | Get device Twin...

What's the problem?

罗宇恒罗宇恒 571 Reputation points

2021-05-19T10:00:56.867+00:00

I'm sorry, I made a mistake.

I do not add any properties in ModuleTwin at IoT Hub side.
After I add any property, I can get both reported properties and desired properties now.

But I still have a problem.
SDK said "this module client will receive a callback each time a desired property is updated" after startTwin.

I try to modify any value of desired properties in ModuleTwin at IoT Hub side, but do not recevie any callback.

What should I do? thanks.
罗宇恒罗宇恒 571 Reputation points

2021-05-20T01:57:58.567+00:00
I try to use the following API:
startTwin(IotHubEventCallback deviceTwinStatusCallback, Object deviceTwinStatusCallbackContext, DeviceTwin.TwinPropertiesCallback genericPropertiesCallBack, Object genericPropertyCallBackContext)

But i met below build error:

[ERROR] COMPILATION ERROR : [INFO] ------------------------------------------------------------- [ERROR] /home/Work/MyEdgeSolution2/modules/MyFirstModule/src/main/java/com/edgemodule/App.java:[8,53] 找不到符号符号: 类 TwinPropertiesCallback 位置: 程序包 com.microsoft.azure.sdk.iot.device.DeviceTwin [INFO] 1 error

How can I fix it?
António Sérgio Azevedo 7,666 Reputation points Microsoft Employee

2021-05-20T12:21:02.17+00:00

Hi @罗宇恒罗宇恒 ,
It is my understanding that you are customizing the sample from here correct?

If you run the sample as is, do you still have compilation errors and you don't receive a notification for desired properties changes on ModuleTwin?

Please note that this Module Twin is related with an Azure IoT Hub Device and not related with a Module on IoT Edge.

See: Understand and use module twins in IoT Hub

Module identity and module twins provide a management separation of concerns when working with IoT devices that have modular software components.

The sample you are using relates with the above.
Thanks!
罗宇恒罗宇恒 571 Reputation points

2021-05-21T01:11:32.897+00:00

Dear asergaz,

Thanks for your feedback.

It is my understanding that you are customizing the sample from here correct?
Yes.

If you run the sample as is, do you still have compilation errors and you don't receive a notification for desired properties changes on ModuleTwin?
As is code do not have compilation errors.
But it don't receive a notification when I add a desired property in ModuleTwin.

I also try to test the C# sample code, and it can receive a notification when I add a desired property in ModuleTwin.

Then I compared the difference between Java sample and C# sample. I found TwinPropertiesCallback is similar with C#'s sample.
So I try to use TwinPropertiesCallback instead of TwinPropertyCallback, but I met above compilation error.

Please help me, thanks.(1000 characters exceeded...)
罗宇恒罗宇恒 571 Reputation points

2021-05-21T08:51:30.147+00:00
Sorry, as-is code can receive notification for desired properties changes on ModuleTwin.

I made a mistake, I comment out the following code:

client.subscribeToTwinDesiredProperties(desiredProperties);

I add this line back, it can receive notification for desired properties changes on ModuleTwin.

But I have a question, what's the difference between the following 2 code?

client.subscribeToTwinDesiredProperties(desiredProperties); client.subscribeToTwinDesiredProperties(null);

Seems the test result are same.

António Sérgio Azevedo 7,666 Microsoft Employee

@罗宇恒罗宇恒 see de definition here

 /**  
     * Subscribes to desired properties  
     *  
     * @param onDesiredPropertyChange the Map for desired properties and their corresponding callback and context. Can be {@code null}.  
     *  
     * @throws IOException if called when client is not opened or called before starting twin.  
     */  
    public void subscribeToTwinDesiredProperties(Map<Property, Pair<TwinPropertyCallBack, Object>> onDesiredPropertyChange) throws IOException  
    {...

António Sérgio Azevedo 7,666 Reputation points Microsoft Employee

2021-05-21T14:51:59.963+00:00

@罗宇恒罗宇恒 I believe you have found the workaround for the initial issue reported in this thread. To make it more clear, can you share and verify the answer with others?

Thanks.

Accepted answer

罗宇恒罗宇恒 571 Reputation points

2021-05-24T01:21:40.907+00:00
We can use the following APIs:

Get Module Twin:
ModuleClient.startTwin(IotHubEventCallback deviceTwinStatusCallback, Object deviceTwinStatusCallbackContext, DeviceTwin.TwinPropertyCallBack genericPropertyCallBack, Object genericPropertyCallBackContext)

Set Module Twin:
InternalClient.sendReportedProperties(Set<DeviceTwin.Property> reportedProperties)

Monitor Module Twin:
InternalClient.subscribeToTwinDesiredProperties(Map<DeviceTwin.Property,DeviceTwin.Pair<DeviceTwin.TwinPropertyCallBack,Object>> onDesiredPropertyChange)

For details we can refer to sample:
https://github.com/Azure/azure-iot-sdk-java/blob/master/device/iot-device-samples/module-twin-sample/src/main/java/samples/com/microsoft/azure/sdk/iot/ModuleTwinSample.java
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[Azure IoT SDK]How can I set/get/monitor the value of ModuleTwin?

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