4.Create Device Shadow using java & spring boot. Interact with Classic and Named Shadow.AWS-IOT-Core

aws-sample: github.com/aws...
A Device Shadow is a persistent, virtual representation of a device that is managed by a thing resource you create in the AWS IoT registry. The Shadow document is a JSON or a JavaScript notation doc that is used to store and retrieve the current state information for a device.
The AWS IoT Device Shadow service adds shadows to AWS IoT thing objects. Shadows can make a device’s state available to apps and other services whether the device is connected to AWS IoT or not. AWS IoT thing objects can have multiple named shadows so that your IoT solution has more options for connecting your devices to other apps and services.
AWS IoT thing objects do not have any named shadows until they are created explicitly; however, an unnamed, classic shadow is created for a thing when the thing is created. Shadows can be created, updated, and deleted by using the AWS IoT console. Devices, other web clients, and services can create, update, and delete shadows by using MQTT and the reserved MQTT topics, HTTP using the Device Shadow REST API, and the AWS CLI for AWS IoT. Because shadows are stored by AWS in the cloud, they can collect and report device state data from apps and other cloud services whether the device is connected or not
Shadows provide a reliable data store for devices, apps, and other cloud services to share data. They enable devices, apps, and other cloud services to connect and disconnect without losing a device's state.
While devices, apps, and other cloud services are connected to AWS IoT, they can access and control the current state of a device through its shadows. For example, an app can request a change in a device's state by updating a shadow. AWS IoT publishes a message that indicates the change to the device. The device receives this message, updates its state to match, and publishes a message with its updated state. The Device Shadow service reflects this updated state in the corresponding shadow. The app can subscribe to the shadow's update or it can query the shadow for its current state.
When a device goes offline, an app can still communicate with AWS IoT and the device's shadows. When the device reconnects, it receives the current state of its shadows so that it can update its state to match that of its shadows, and then publish a message with its updated state. Likewise, when an app goes offline and the device state changes while it's offline, the device keeps the shadow updated so the app can query the shadows for its current state when it reconnects.
Choosing to use named or unnamed shadows
The Device Shadow service supports named and unnamed, classic shadows, as have been used in the past. A thing object can have multiple named shadows, and no more than one unnamed, classic shadow. A thing object can have both named and unnamed shadows at the same time; however, the API used to access each is slightly different, so it might be more efficient to decide which type of shadow would work best for your solution and use that type only. For more information about the API to access the shadows, see Shadow topics.
With named shadows, you can create different views of a thing object’s state. For example, you could divide a thing object with many properties into shadows with logical groups of properties, each identified by its shadow name. You could also limit access to properties by grouping them into different shadows and using policies to control access. Named shadows, however, do not support fleet indexing.
The classic, unnamed shadows are simpler, but somewhat more limited than the named shadows. Each AWS IoT thing object can have only one unnamed shadow. If you expect your IoT solution to have a limited need for shadow data, this might be how you want to get started using shadows. However, if you think you might want to add additional shadows in the future, consider using named shadows from the start.
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Hey! How could i read from a shadow? I mean get the current state, i think it would be would the "/get" topic right? But how do I use it?