Module storm.foundation
Package st.orm.mapping

Interface Instantiator<T>

Type Parameters:
T - the record type this instantiator constructs.
public interface Instantiator<T>
Constructs record instances without reflection.

The metamodel generators emit an implementation per record type that invokes the record's canonical constructor (the primary constructor for Kotlin data classes) directly, registered through META-INF/services/st.orm.mapping.Instantiator. The row mapper dispatches to a registered instantiator instead of Constructor.newInstance, so applications run without reflective construction: no reflection configuration for native images, and no opens clauses for modular applications.

When no instantiator is registered for a type, the row mapper falls back to reflective construction, so models compiled without the generators keep working unchanged.

Since:
1.13

  • Method Summary

    Modifier and Type
    Method
    Description
    default @Nullable Object @Nullable []
    deconstruct(T instance)
    Deconstructs the given instance into its canonical constructor arguments, in declaration order.
    T
    instantiate(@Nullable Object[] args)
    Constructs a new instance from the canonical constructor arguments.
    Class<T>
    type()
    Returns the record type this instantiator constructs.

  • Method Details

    • type

      Class<T> type()
      Returns the record type this instantiator constructs.
      Returns:
      the constructed record type.

    • instantiate

      T instantiate(@Nullable Object[] args)
      Constructs a new instance from the canonical constructor arguments.

      The arguments are positional and fully adapted: the caller has already performed null checks and type conversion, so implementations only cast and invoke the constructor.

      Parameters:
      args - the canonical constructor arguments, in declaration order; elements are null where the corresponding component is.
      Returns:
      the constructed instance.

    • deconstruct

      default @Nullable Object @Nullable [] deconstruct(T instance)
      Deconstructs the given instance into its canonical constructor arguments, in declaration order.

      Generated instantiators override this to read the components directly, completing the reflection-free round trip for record rebuilds: component reads run as generated code, matching instantiate(java.lang.Object[]) on the construction side. The returned array is freshly allocated; callers may modify it and pass it to instantiate(java.lang.Object[]) to build an adjusted copy of the instance.

      The default returns null, signalling that no generated deconstructor is available; callers fall back to reflective component access.

      Parameters:
      instance - the instance to deconstruct.
      Returns:
      the component values in declaration order, or null when not supported.
      Since:
      1.13