public Class IdentityGenerator

Overrides default org.hibernate.generator.OnExecutionGenerator.getGeneratedIdentifierDelegate.

Doc from org.hibernate.generator.OnExecutionGenerator.getGeneratedIdentifierDelegate.

The InsertGeneratedIdentifierDelegate used to retrieve the generated value if this object is an identifier generator.

This is ignored by org.hibernate.metamodel.mapping.internal.GeneratedValuesProcessor, which handles multiple generators at once. So if this object is not an identifier generator, this method is never called.

Note that this method arguably breaks the separation of concerns between the generator and coordinating code, by specifying how the generated value should be retrieved.

The problem solved here is: we want to obtain an insert-generated primary key. But, sadly, without already knowing the primary key, there's no completely-generic way to locate the just-inserted row to obtain it.

We need one of the following things:

• a database which supports some form of insert ... returning syntax, or can do the same thing using the JDBC getGeneratedKeys() API, or
• a second unique key of the entity, that is, a property annotated @NaturalId.

Alternatively, if the generated id is an identity/"autoincrement" column, we can take advantage of special platform-specific functionality to retrieve it. Taking advantage of the specialness of identity columns is the job of one particular implementation: org.hibernate.id.IdentityGenerator. And the need for customized behavior for identity columns is the reason why this layer-breaking method exists.

Annotations

@Override

Implements org.hibernate.generator.OnExecutionGenerator.getReferencedColumnValues.

Doc from org.hibernate.generator.OnExecutionGenerator.getReferencedColumnValues.

A SQL expression indicating how to calculate the generated values when the mapped columns are included in the SQL statement. The SQL expressions might be:

• function calls like current_timestamp or nextval('mysequence'), or
• syntactic markers like default.

Parameters

dialect:Dialect

The SQL dialect, allowing generation of an expression in dialect-specific SQL.

Returns:String[]

The column value to be used in the generated SQL statement.

Annotations

@Override

Implements org.hibernate.generator.OnExecutionGenerator.referenceColumnsInSql.

Doc from org.hibernate.generator.OnExecutionGenerator.referenceColumnsInSql.

Determines if the columns whose values are generated are included in the column list of the SQL insert or update statement. For example, this method should return:

• true if the value is generated by calling a SQL function like current_timestamp, or
• false if the value is generated by a trigger, by generated always as, or using a column default value.

Returns:boolean

true if the column is included in the column list of the SQL statement.

Annotations

@Override