All Superinterfaces:

Serializable

All Known Subinterfaces:

AnnotationBasedGenerator<A>, AnnotationValueGeneration<A>, BeforeExecutionGenerator, BulkInsertionCapableIdentifierGenerator, IdentifierGenerator, OnExecutionGenerator, OptimizableGenerator, PersistentIdentifierGenerator, PostInsertIdentifierGenerator, ValueGeneration

All Known Implementing Classes:

AbstractUUIDGenerator, Assigned, CompositeNestedGeneratedValueGenerator, CreationTimestampGeneration, CurrentTimestampGeneration, ForeignGenerator, GeneratedAlwaysGeneration, GeneratedGeneration, GUIDGenerator, IdentityGenerator, IncrementGenerator, OrderedSequenceGenerator, SelectGenerator, SequenceStyleGenerator, SourceGeneration, TableGenerator, TenantIdGeneration, UpdateTimestampGeneration, UuidGenerator, UUIDGenerator, UUIDHexGenerator, VersionGeneration, VmValueGeneration
```
public interface Generator
extends Serializable
```
Describes the generation of values of a certain field or property of an entity. A generated value might be generated in Java, or by the database. Every instance must implement either BeforeExecutionGenerator or OnExecutionGenerator depending on whether values are generated in Java code before execution of a SQL statement, or by the database when the SQL statement is executed.
- Value generation via arbitrary code written in Java is the responsibility of the method BeforeExecutionGenerator.generate(SharedSessionContractImplementor, Object, Object, EventType). In this case, the generated value is written to the database just like any other field or property value. The Java code may, of course, ask the database to actually generate the value. Examples include timestamp generation using the JVM system time, and id generation using a database sequence.
- A value generated by the database might be generated implicitly, by a trigger, or using a default column value specified in DDL, for example, or it might be generated by a SQL expression occurring explicitly in the SQL insert or update statement. In this case, the generated value may be retrieved from the database using a SQL select, though in certain cases this additional round trip may be avoided. An important example is id generation using an identity column.
Generically, a generator may be integrated with the program using the meta-annotation ValueGenerationType, which associates the generator with a Java annotation type, called the generator annotation. A generator may receive parameters from its generator annotation. The generator may either:
- implement AnnotationBasedGenerator, and receive the annotation as an argument to AnnotationBasedGenerator.initialize(A, java.lang.reflect.Member, org.hibernate.generator.GeneratorCreationContext),
- declare a constructor with the same signature as AnnotationBasedGenerator.initialize(A, java.lang.reflect.Member, org.hibernate.generator.GeneratorCreationContext),
- declare a constructor which accepts just the annotation instance, or
- declare a only default constructor, in which case it will not receive parameters.
A generator must implement getEventTypes() to specify the events for which it should be called to produce a new value. EventTypeSets provides a convenient list of possibilities.
There are two especially important applications of this machinery:
- An identifier generator is a generator capable of producing surrogate primary key values. An identifier generator must respond to insert events only. That is, getEventTypes() must return EventTypeSets.INSERT_ONLY. It may be integrated using the IdGeneratorType meta-annotation or the older-style GenericGenerator annotation.
- A version generator is a generator capable of seeding and incrementing version numbers. A version generator must respond to both insert and update events. That is, getEventTypes() must return EventTypeSets.INSERT_AND_UPDATE. It may be integrated using ValueGenerationType meta-annotation.
Since:

6.2

See Also:

ValueGenerationType, IdGeneratorType, Generated

Method Summary

All Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method	Description
`boolean`	`generatedOnExecution()`	Determines if the property value is generated when a row is written to the database, or in Java code that executes before the row is written.
`default boolean`	`generatesOnInsert()`
`default boolean`	`generatesOnUpdate()`
`default boolean`	`generatesSometimes()`
`EnumSet<EventType>`	`getEventTypes()`	The event types for which this generator should be called to produce a new value.

- Method Detail
  - generatedOnExecution
```
boolean generatedOnExecution()
```
    Determines if the property value is generated when a row is written to the database, or in Java code that executes before the row is written.
    
    Generators which only implement BeforeExecutionGenerator must result false.
    Generators which only implement OnExecutionGenerator must result true.
    Generators which implement both subinterfaces may decide at runtime what value to return.
    Returns:
    
    true if the value is generated by the database as a side effect of the execution of an insert or update statement, or false if it is generated in Java code before the statement is executed via JDBC.
  - getEventTypes
```
EnumSet<EventType> getEventTypes()
```
    The event types for which this generator should be called to produce a new value.
    Identifier generators must return EventTypeSets.INSERT_ONLY.
    
    Returns:
    
    a set of EventTypes.
  - generatesSometimes
```
default boolean generatesSometimes()
```
  - generatesOnInsert
```
default boolean generatesOnInsert()
```
  - generatesOnUpdate
```
default boolean generatesOnUpdate()
```

Interface Generator

Method Summary

Method Detail

generatedOnExecution

getEventTypes

generatesSometimes

generatesOnInsert

generatesOnUpdate