My problem is that because the previous transaction has not ended yet, a new transaction cannot be started, so no matter what, an error must be reported. Add the @Transactional(propagation=Propagation.NOT_SUPPORTED) annotation on the service layer to start a new transaction, and it will be fine.

You don’t insert操作吗？为什么要使用readOnly=true。这表示只读事务。不能用于写操作。
把readOnlyjust remove it and it will be ok.

Check your database permissions! Does it only have read-only permissions? I can't see any problem with the code.