Mapping PostgreSQL serial type with Hibernate anno

问题:

I am using Hibernate 3.3 and PostgreSQL 8.x and would like to use Hibernate annotations to map an auto-incremented column which is NOT a primary key.

It doesn't matter if the column is mapped using SERIAL type or sequences in Postgres as long as it gets auto-incremented by the database and not by Hibernate. I tried the following mappings, but they always generated null orderId.

@Column(name = "orderId", insertable = false)
@Generated(GenerationTime.INSERT)
//@GeneratedValue(strategy = javax.persistence.GenerationType.AUTO)
private Integer orderId;

I will appreciate any help with this.

Thanks

回答1:

The following mapping should work fine:

@Column(name = "orderId")
@Generated(GenerationTime.INSERT)
private Integer orderId;

Note, however, that generated value for freshly saved objects is not available until session is flushed.

EDIT: Note that this mapping doesn't affect doesn't make Hibernate to create a column of type serial during schema generation, since Hibernate doesn't know anything about the nature of value generation at the database side. Therefore, if you want Hibernate to create a column with a proper type, you need to specifiy it explicitly:

@Column(name = "orderId", columnDefinition = "serial")
@Generated(GenerationTime.INSERT)
private Integer orderId;

And on a recent Hibernate version (4.3), you can use this:

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private Long orderId;

回答2:

the accepted answer doesn't work for me.

this did though:

@Id
@Column(name = "your_id", columnDefinition = "serial")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer yourId;

回答3:

I'm using this with postgresql9.1, should work with 8 too:

@SequenceGenerator(allocationSize=1, initialValue=1, sequenceName="account_id_seq", name="account_id_seq")
@GeneratedValue(generator="account_id_seq", strategy=GenerationType.SEQUENCE)
@Id
@Column(name="id")
private Integer id;