The auto-increment primary key of Hibernate is not controlled by users.

If the HBM file of hibernate says generate class = "increment", Hibernate will first find the maximum id value each time a record is inserted, for example:
Select max (user_id) from example_user.

Insert a record.

In this case, the value of the primary key is not controlled by the user. For example, the largest record in the database is 1, admin, admin. however, we add a new record, the number of new records 5, uesr, and uesr. hibernate won't let you jump to increase, result 2, uesr, uesr. hibernate. cfg. add a propertry name = "show_ SQL" to sessionfactory in XML, and set the value to true.