FYI
If you are using hbm files to define the O/R mapping.
Notice that:
In Hibernate 5, the param name for the sequence name has been changed.
The following setting worked fine in Hibernate 4:
<generator class="sequence">
<param name="sequence">xxxxxx_seq</param>
</generator>
But in Hibernate 5, the same mapping setting file will cause a "hibernate_sequence doesn't exist" error.
To fix this error, the param name must change to:
<generator class="sequence">
<param name="sequence_name">xxxxxx_seq</param>
</generator>
This problem wasted me 2, 3 hours.
And somehow, it looks like there are no document about it.
I have to read the source code of org.hibernate.id.enhanced.SequenceStyleGenerator to figure it out