Defines a named identifier generator, usually an instance of the interface org.hibernate.id.IdentifierGenerator. This allows the use of custom identifier generation strategies beyond those provided by the four basic JPA-defined generation types.

A named generator may be associated with an entity class by:

• defining a named generator using this annotation, specifying an implementation of IdentifierGenerator using type, then
• annotating the identifier property of the entity with the JPA-defined @GeneratedValue annotation, and
• using generator to specify the name() of the generator defined using this annotation.

If neither type not strategy is specified, Hibernate asks the dialect to decide an appropriate strategy. This is equivalent to using AUTO in JPA.

For example, if we define a generator using:

@GenericGenerator(name = "custom-generator",
                  type = org.hibernate.eg.CustomStringGenerator.class)
}

Then we may make use of it by annotating an identifier field as follows:

@Id @GeneratedValue(generator = "custom-generator")
private String id;

The disadvantage of this approach is the use of stringly-typed names. An alternative, completely typesafe, way to declare a generator and associate it with an entity is provided by the IdGeneratorType meta-annotation.