hibernate ID生成策略配置

1.Student.hbm.xml配置

<hibernate-mapping package="com.wxh.hibernate.model">
	<class name="Student" >
		<id name="id">
		<generator class="uuid"></generator>
		</id>
		<property name="age"></property>
		<property name="name"></property>
	</class>
</hibernate-mapping>

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.

id的类型要为String类型，最终在mysql中产生的id为varchar类型。

<hibernate-mapping package="com.wxh.hibernate.model">
	<class name="Student" >
		<id name="id">
		<generator class="uuid"></generator>
		</id>
		<property name="age"></property>
		<property name="name"></property>
	</class>
</hibernate-mapping>

native

selects

identity

,

sequence

or

hilo

depending
upon the capabilities of the underlying database.

2.Annotation配置_IDENTITY_SEQUENCE

@Id
	@GeneratedValue(strategy=GenerationType.IDENTITY)
	public int getId() {
		return id;
	}

Sequence生成器，使用oracle数据库。

@SequenceGenerator（name=”teacherSEQ”,sequenceName=”teacherSEQ_DB”）加在类前



@GeneratedValue（strategy=GenerationType.SEQUENCE,generator=”teacherSEQ”）加在方法前

3.TableGenerator（跨数据库平台）
@javax.persistence.TableGenerator(

name="Teacher_GEN",

table="GENERATOR_TABLE",

pkColumnName="pk_key",

valueColumnName="pk_value",

pkColumnValue="Teacher",

allocationSize=1

)