hibernate注解(annoation)使用id主键生成策略

hibernate注解(annoation)使用id主键生成主要要使用到以下几个注解: @Id,@GeneratedValue,@GenericGenerator. ,@GeneratedValue的作用是JPA的默认实现自定义主键生成策略,@GenericGenerator是hibernate在JPA的基础上增强。

自定义主键生成策略，由@GenericGenerator实现。hibernate在JPA的基础上进行了扩展，可以用一下方式引入hibernate独有的主键生成策略，就是通过@GenericGenerator加入的。

比如说，JPA标准用法

@Id
@GeneratedValue (GenerationType.AUTO)

就可以用hibernate特有以下用法来实现

@GeneratedValue (strategy = GenerationType.AUTO)
@GenericGenerator (name = "paymentableGenerator" , strategy = "native" )

使用@GeneratedValue

1、针对mysql,oracle,sqlserver数据库可以同时使用

@Id
@GeneratedValue (strategy = GenerationType.AUTO)
@GenericGenerator (name = "paymentableGenerator" , strategy = "native" )

name属性指定生成器名称。

strategy属性指定具体生成器的类名。

parameters得到strategy指定的具体生成器所用到的参数。

2、配合使用@GenericGenerator 不单独使用

对于这些hibernate主键生成策略和各自的具体生成器之间的关系,在org.hibernate.id.factory.internal.DefaultIdentifierGeneratorFactory中指定了:

//Constructs a new DefaultIdentifierGeneratorFactory.
    public DefaultIdentifierGeneratorFactory() {
        register( "uuid2" , UUIDGenerator. class );
        register( "guid" , GUIDGenerator. class );
        register( "uuid" , UUIDHexGenerator. class );
        register( "uuid.hex" , UUIDHexGenerator. class );
        register( "hilo" , TableHiLoGenerator. class );
        register( "assigned" , Assigned. class );
        register( "identity" , IdentityGenerator. class );
        register( "select" , SelectGenerator. class );
        register( "sequence" , SequenceGenerator. class );
        register( "seqhilo" , SequenceHiLoGenerator. class );
        register( "increment" , IncrementGenerator. class );
        register( "foreign" , ForeignGenerator. class );
        register( "sequence-identity" , SequenceIdentityGenerator. class );
        register( "enhanced-sequence" , SequenceStyleGenerator. class );
        register( "enhanced-table" , TableGenerator. class );
    }

如果想要不同的表使用相同的主键生成器，可以把他的generator的name属性设为相同即可，例如：

@GeneratedValue (name= "id1" )
@GenericGenerator (name= "id1" ,strategy= "identity" )

上面十二种策略，加上native，hibernate一共默认支持十三种生成策略

1、native

@GeneratedValue (generator = "paymentableGenerator" )
@GenericGenerator (name = "paymentableGenerator" , strategy = "native" )

2、uuid

@GeneratedValue (generator = "paymentableGenerator" )
@GenericGenerator (name = "paymentableGenerator" , strategy = "uuid" )

3、hilo

@GeneratedValue (generator = "paymentableGenerator" )
@GenericGenerator (name = "paymentableGenerator" , strategy = "hilo" )

4、assigned

@GeneratedValue (generator = "paymentableGenerator" )
@GenericGenerator (name = "paymentableGenerator" , strategy = "assigned" )

5、identity

@GeneratedValue (generator = "paymentableGenerator" )
@GenericGenerator (name = "paymentableGenerator" , strategy = "identity" )

6、select

@GeneratedValue (generator = "paymentableGenerator" )
@GenericGenerator (name= "select" , strategy= "select" , parameters = { @Parameter (name = "key" , value = "idstoerung" ) })

7、sequence

@GeneratedValue (generator = "paymentableGenerator" )
@GenericGenerator (name = "paymentableGenerator" , strategy = "sequence" , parameters = { @Parameter (name = "sequence" , value = "seq_payablemoney" ) })

8、seqhilo

@GeneratedValue (generator = "paymentableGenerator" )
@GenericGenerator (name = "paymentableGenerator" , strategy = "seqhilo" , parameters = { @Parameter (name = "max_lo" , value = "5" ) })

9、increment

@GeneratedValue (generator = "paymentableGenerator" )
@GenericGenerator (name = "paymentableGenerator" , strategy = "increment" )