Locking a table with hibernate
You need to use pessimistic locking, which can be achieved by
setLockMode(String alias, LockMode lockMode) on the query and use LockMode.UPGRADE.
However, this will certainly kill scalability and performance if you are doing a lot of access on this table. You are better either using a sequence or another strategy is to create a service to allocate numbers (e.g., an SSB) which grabs 100 numbers at a time, updates the database, and hands them out. That saves you 198 database accesses.
UPDATE:
You will also have to modify your table design slightly. It is better to have a single row with a known ID and to store the number you are incrementing in another column. Then you should update the row rather than deleting the old row and adding a new one. Otherwise, the row locking strategy won't work.
UPDATE2:
OP found that the following worked:
session.get(class.Class, id, lockOption)