I do not believe that the Hibernate Reference PDF differentiates between the persist() and save() methods well enough for a developer to determine which one to use and where. This information would be extremely useful in section 10.2 "Making objects persistent" where these two methods are described.
I found that a lot of people have the same doubt. To help to solve this issue I'm quoting Christian Bauer:
"In case anybody finds this thread...
persist() is well defined. It makes a transient instance persistent. However, it doesn't guarantee that the identifier value will be assigned to the persistent instance immediately, the assignment might happen at flush time. The spec doesn't say that, which is the problem I have with persist().
persist() also guarantees that it will not execute an INSERT statement if it is called outside of transaction boundaries. This is useful in long-running conversations with an extended Session/persistence context.
A method like persist() is required.
save() does not guarantee the same, it returns an identifier, and if an INSERT has to be executed to get the identifier (e.g. "identity" generator, not "sequence"), this INSERT happens immediately, no matter if you are inside or outside of a transaction. This is not good in a long-running conversation with an extended Session/persistence context."
Bulk closing stale resolved issues