Custom Java Module

Akhil 1

How the data is getting sent when using custom java module is created?

1 answer

Sander van de Velde | MVP 32,726 Reputation points MVP

2021-11-12T08:10:33.513+00:00

Hello @Akhil ,

I understand you want to build an Azure IoT Edge module using the Java language.

If you have added the Azure IoT Edge extension to Visual Studio Code, you are able to create this sample module in various programming languages, including Java:

Check out this tutorial for more information about creating a module.

Azure IoT Edge modules are in fact Docker containers. Because these custom modules, using a VS Code template, support Azure IoT Edge SDKs, each module can communicate with the default available edgeHub module.

This edheHub module stays in contact with the Azure IoT Hub a acts as a message broker.

There is a routing mechanism in place to pass messages on from module to module (see inputs and outputs).

If you add support for one or more inputs and outputs, you can pick up messages and send them to other modules and/or the cloud.
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Akhil 1 Reputation point

2021-11-12T09:24:31.733+00:00

For example, I have an edge device that contains 3 modules mainly $edgeHub,$edgeAgent and a custom Java module which is developed referring to your document. I just wanted to know how can I send any data from java to the custom module.

In the document, it's said that the method in the module is triggered when it receives an MQTT message from $edgeHub. It is unclear in the document how to send data to $edgeHub.
If we somehow make this work then we are actually planning to include Azure in our project.

Sander van de Velde | MVP 32,726 Reputation points MVP

2021-11-12T13:05:12.537+00:00

Hello @Akhil ,

Azure IoT Edge modules can do everything a normal Docker container can. The only special part is ability to connect to the iot edge internal routing mechanism with D2C and C2D communication (on container level).

So, you are able to eg. access volumes on disk, do network communication, exposing websites or webservices or MQTT or UDP or whatever. You can also access the physical world like serial ports.

Keep in mind the normal Docker environment variables and container create options still apply.

So, for example, if you want to expose a port, you need to configure it. The same goes for volume bindings. This can all be done from the Azure portal / Cloud; Zero touch.

I have built multiple modules; some do web sockets or UDP or serial communication. The data which is received is then ingested als JSON messages to the next module, using routing, for further analysis.

If you add a route from a custom module output to '$upstream', messages are then automatically forwarded to the Azure IoT Hub. If the connection is temporarily broken, messages are stored for the being locally. Once the connection is back, messages are sent, nothing is lost.
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Custom Java Module

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