From this forum conversation, I realized that DefaultIdentifierGeneratorFactory does not take into consideration the hibernate.id.new_generator_mappings setting.
When porting from Hibernate 3.x or 4.x to 5.x, users will bump into this issue since sequence will evaluate to SequenceStyleGenerator, which uses different parameter names than the now-deprecated SequenceGenerator which has been previously the default option.
does this affect 5.0?
This issue affects both 5.0 and 5.1.
Re-opening to add more fix versions.
Fixed in 5.1 and 5.0 branches as well.