Hibernate 主键generator类型

increment
用于为long, short或者int类型生成 唯一标识。只有在没有其他进程往同一张表中插入数据时
才能使用。 在集群下不要使用。

identity
对DB2,MySQL, MS SQL Server, Sybase和HypersonicSQL的内置标识字段提供支持。 返回的标
识符是long, short 或者int类型的。

sequence
在DB2,PostgreSQL, Oracle, SAP DB, McKoi中使用序列（sequence)， 而在Interbase中使用
生成器(generator)。返回的标识符是long, short或者 int类型的。

hilo
使用一个高/低位算法高效的生成long, short 或者 int类型的标识符。给定一个表和字段（默
认分别是 hibernate_unique_key 和next_hi）作为高位值的来源。 高/低位算法生成的标识符
只在一个特定的数据库中是唯一的。

seqhilo
使用一个高/低位算法来高效的生成long, short 或者 int类型的标识符，给定一个数据库序列
（sequence)的名字。

uuid
uses a 128-bit UUID algorithm to generate identifiers of type string that are unique
within a network (the IP address is used). The UUID is encoded as a string of 32
hexadecimal digits in length.

guid
在MS SQL Server 和 MySQL 中使用数据库生成的GUID字符串。

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.

select
retrieves a primary key, assigned by a database trigger, by selecting the row by
some unique key and retrieving the primary key value.

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

sequence-identity
a specialized sequence generation strategy that utilizes a database sequence for the
actual value generation, but combines this with JDBC3 getGeneratedKeys to return
the generated identifier value as part of the insert statement execution. Thisidstrategy is only supported on Oracle 10g drivers targeted for JDK 1.4. Comments on
these insert statements are disabled due to a bug in the Oracle drivers.