Oracle系列：（24）序列

identity

supports identity columns in DB2, MySQL, MS SQLServer, Sybase and HypersonicSQL. The returned identifier is of type long, short or int.

sequence

uses a sequence in DB2, PostgreSQL, Oracle, SAP DB, McKoi or a generator in Interbase. The returned identifier is of type long, short or int

uuid

Generates a 128-bit UUID based on a custom algorithm. The value generated is represented as a string of 32 hexidecimal digits. Users can also configure it to use a separator (config parameter "separator") which separates the hexidecimal digits into 8{sep}8{sep}4{sep}8{sep}4. 

uuid2

Generates a IETF RFC 4122 compliant (variant 2) 128-bit UUID. The exact "version" (the RFC term) generated depends on the pluggable "generation strategy" used. Capable of generating values as java.util.UUID, java.lang.String or as a byte array of length 16 (byte[16]). The "generation strategy" is defined by the interface org.hibernate.id.UUIDGenerationStrategy.

guid

uses a database-generated GUID string on MS SQL Server and MySQL.

native

selects identity,sequence or hilo depending upon the capabilities of the underlying database.

assigned

lets the application assign an identifier to the object before save() is called. This is the default strategy if no <generator> element is specified.

foreign

uses the identifier of another associated object. It is usually used in conjunction with a <one-to-one> primary key  association.