Was recently pondering if it were possible to auto-generate a client for the AWS API.
I decided to see how the official SDKs were made, and found out that Amazon created a tool called Smithy: https://github.com/awslabs/smithy
They've written their more recent SDKs via code generation in Smithy, see for example:
The base Go generator: https://github.com/aws/smithy-go
The generation specifically for the Go SDK: https://github.com/aws/aws-sdk-go-v2/tree/main/codegen
This is too much effort for me to personally bother with (plus I barely know Java), but I thought it might take someone else's interest, especially since I struggled to find any hint of this being a thing in the first place.