Flush() Vs Commit()

flush() will send the the changes to the database but not commiting yet

commit() will commit those changes into the database. This will automatically call flush() as well

By default of a @Transactional. After a transaction ends it will automatically commit().

What happen between flush() and commit()

These are the UNCOMMITED changes. Since Transaction are executed in isolation, when you call flush() but haven't called commit() yet, the other transaction might or might not see the changes depends on the isolation level:

• READ_UNCOMMITED: will see the changes from flush()
• READ_COMMITED: will not see the changes from flush()

If the other transaction don't specify, the default behavior of Spring is to use DEFAULT which will use the database default's isolation.