[jboss-user] [EJB 3.0] - Re: Problem using SequenceGenerator

[bryan_castillo]

Ok, now I know whats going on.

To summarize, I thought that a generated id coming from a sequence in EJB would be the same as the physical value of the sequence.  But the sequence generator actually takes the value from the database sequence and multiplies it by the allocationSize.  As long as every program, (or chunk of code) using that sequence uses the same multiplier you will be safe.  The SequenceHiLoGenerator keeps the last sequence number in memory and just increments the sequence number in memory, and pulls a new physical sequence when it uses allocationSize numbers since the last pull from the physical sequence.

If I want the generator to produce the same number as the sequence (so the code will not conflict with other non-java code using the sequence), than I can set the allocationSize to 1.  Then I will not need a hibernate specific annotation. 

This works for me:

  | 	@Id
  | 	@GeneratedValue(strategy=GenerationType.SEQUENCE, generator="VNDR_ID_SEQ")
  | 	@SequenceGenerator(name="VNDR_ID_SEQ", sequenceName="VRAP.VNDR_ID_SEQ", allocationSize=1)
  | 	@Column(name="VNDR_ID")
  | 	public int getId() {
  | 		return id;
  | 	}

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