Inventory Sync - This plugin synchronizes the player inventory with a database

Cannot use the new mysql8.0, ‘unknown system variable’ tx_isolation '. I hope to update my MySQL support.

Welcome to the Sponge community!

Now onto your issue: Since I use Sponge’s built in MySQL driver they need to provide support for that.
Try updating Sponge and if that doesn’t help bring it up with the Sponge devs.

Hi!
I have 1 question - how deserialize data (i wanna use for website)?
I need only players items.

Sorry for the late response. I somehow didn’t see a notification for this message.

The data is stored in gzip compressed NBT format. Any NBT reader should be able to read it as is, as gzip compression is part of the spec.