Separate DataAcc, which will only provide the GetDataConn method, from DataHub, which will only provide the Run and Txn methods.

[sttk]

Currently, DataAcc is an interface that declares the getDataConn method, and DataHub inherits from it. Therefore, a DataHub instance can use getDataConn directly, while a method that receives the instance as a DataAcc can also use run and txn by downcasting it to DataHub. This is a problematic design.

In the Go version of sabi, in order to change sabi.GetDataConn, sabi.Run, and sabi.Txn into the generic methods DataAcc#GetDataConn, DataHub#Run, and DataHub#Txn, I changed DataAcc from an interface to a struct and separated it from DataHub, which has a DataAcc instance as a field. This change eliminates the problematic design in the Go version.

Therefore, I'll make the same change to the Java version.

[sttk]

See sttk/sabi-rust#138