Package org.hibernate.generator

Interface OnExecutionGenerator

All Superinterfaces:
Generator,Serializable
All Known Subinterfaces:
PostInsertIdentifierGenerator
All Known Implementing Classes:
AbstractPostInsertGenerator,CurrentTimestampGeneration,GeneratedAlwaysGeneration,GeneratedGeneration,IdentityGenerator,NativeGenerator,SelectGenerator
public interfaceOnExecutionGeneratorextendsGenerator
A generator which produces a new value by actually going ahead and writing a row to the database, then retrieving the value which was generated by the database itself as a side effect of the SQLinsert orupdate statement which wrote the row.

A value generated by the database might be generated implicitly, by a trigger, or using adefault column value specified in DDL, for example, or it might be generated by a SQL expression occurring explicitly in the SQLinsert orupdate statement.

The generated value is usually retrieved from the database using a SQLselect, but incertain cases this additional round trip may be avoided.

Implementations should overridereferenceColumnsInSql(Dialect),writePropertyValue(), andgetReferencedColumnValues(Dialect) as needed in order to achieve the desired behavior.

In implementation of this interface does not specify how the generated value is retrieved from the database after it is generated, this being the responsibility of the coordinating code inGeneratedValuesProcessor or in an implementation ofInsertGeneratedIdentifierDelegate.

Since:
6.2

  • Method Details

    • referenceColumnsInSql

      boolean referenceColumnsInSql(Dialect dialect)
      Determines if the columns whose values are generated are included in the column list of the SQLinsert orupdate statement. For example, this method should return:
      Returns:
      true if the column is included in the column list of the SQL statement.

    • writePropertyValue

      boolean writePropertyValue()
      Determines if the property values are written to JDBC as the argument of a JDBC? parameter.

    • getReferencedColumnValues

      String[] getReferencedColumnValues(Dialect dialect)
      A SQL expression indicating how to calculate the generated values when the mapped columns areincluded in the SQL statement. The SQL expressions might be:
      • function calls likecurrent_timestamp ornextval('mysequence'), or
      • syntactic markers likedefault.
      Parameters:
      dialect - TheSQL dialect, allowing generation of an expression in dialect-specific SQL.
      Returns:
      The column value to be used in the generated SQL statement.

    • getGeneratedIdentifierDelegate

      @Incubatingdefault InsertGeneratedIdentifierDelegate getGeneratedIdentifierDelegate(EntityPersister persister)
      TheInsertGeneratedIdentifierDelegate used to retrieve the generated value if this object is an identifier generator.

      This is ignored byGeneratedValuesProcessor, 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 beretrieved.

      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:

      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:IdentityGenerator. And the need for customized behavior for identity columns is the reason why this layer-breaking method exists.

    • getUniqueKeyPropertyNames

      @Incubatingdefault String[] getUniqueKeyPropertyNames(EntityPersister persister)
      The name of a property of the entity which may be used to locate the just-inserted row containing the generated value. Of course, the columns mapped by this property should form a unique key of the entity.

      The default implementation uses the@NaturalId property, if there is one.

    • generatedOnExecution

      default boolean generatedOnExecution()
      Description copied from interface: Generator
      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 implementBeforeExecutionGenerator must resultfalse.
      • Generators which only implementOnExecutionGenerator must resulttrue.
      • Generators which implement both subinterfaces may decide at runtime what value to return.
      Specified by:
      generatedOnExecution in interface Generator
      Returns:
      true if the value is generated by the database as a side effect of the execution of aninsert orupdate statement, or false if it is generated in Java code before the statement is executed via JDBC.