Difference between @GeneratedValue and @GenericGenerator

Question

Sometimes I find them together, sometimes alone... other times they seem to do the same.

What\'s the difference?

Here are three examples. What do they do of

Answer 1

@Entity
@Table(name="Honey")
public class Honey implements Serializable{
    private static final long serialVersionUID = 42L;
    @Id
    //@SequenceGenerator(name="honeySequence",sequenceName="HONEY_SEQ")
    @org.hibernate.annotations.GenericGenerator(name="honeySequence", strategy = "sequence", 
    parameters = { 
            @Parameter(name="sequence", value="HONEY_SEQ") } 
    )
    @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="honeySequence")
    private int Id;
    private String name;
    private String taste;

• @GeneratedValue is used only to get the generated value. The two arguments strategy and generator are used to define how the value is obtained.
• @GenericGenerator is used to map a user defined sequence generator with your hibernate session.
• You can also use @SequenceGenerator which i have commented in my code. This is not a simple sequence generator but a generator which work on HILO algorithm. Due to which you will find a lot of gaps in your sequence, like your first value will start from 50 because the default allocation size is 50.

So its better to use @GenericGenerator for your own architecture. But if you are bound to use @SequenceGenerator you have to manually edit your sequence to have two more attributes allocationSize=1 and initialValue=1. And to work with these attributes you need to add apropert in your hibernate.cfg.xml file

true