exposed-core/org.jetbrains.exposed.v1.core/NonNullableColumnWithTransform

NonNullableColumnWithTransform

open class NonNullableColumnWithTransform<Unwrapped, Wrapped>(delegate: IColumnType<Unwrapped & Any>, transformer: ColumnTransformer<Unwrapped, Wrapped>) : ColumnWithTransform<Unwrapped, Wrapped>

A column type that handles the transformation of a nullable database column into a non-nullable Kotlin type.

Unlike NullableColumnWithTransform, which maps null database values to null on the Kotlin side, this type allows the transformer to map a null from the database to a concrete non-null value (e.g., an empty string, a default object, a sentinel value, etc.).

This enables the use-case where a nullable DB column is exposed as a non-nullable property in Kotlin, with a "special value" representing the null state.

For example:

object Users : Table() {
    val description = text("description")
        .nullable()
        .nonNullTransform(
            wrap = { it?.trim()?.ifEmpty { null } ?: "" },
            unwrap = { if (it.isEmpty()) null else it }
        )
}

Here the DB column remains nullable, but the Kotlin type is String (non-nullable). A null in the database maps to "" on the Kotlin side, and an empty string maps back to null when written.

Parameters

delegate

The original column's IColumnType

transformer

Instance of ColumnTransformer that handles null → non-null mapping

Type Parameters

Wrapped

The non-nullable type to which the column value is transformed

Unwrapped

The nullable type of the underlying database column

Constructors

NonNullableColumnWithTransform

constructor(delegate: IColumnType<Unwrapped & Any>, transformer: ColumnTransformer<Unwrapped, Wrapped>)

Properties

delegate

val delegate: IColumnType<Unwrapped & Any>

isAutoInc

val IColumnType<*>.isAutoInc: Boolean

Returns true if this is an auto-increment column, false otherwise.

nullable

open override var nullable: Boolean

Returns true if the column type is nullable, false otherwise.

originalColumnType

val originalColumnType: IColumnType<Any>

Gets the original column type that this column with transformation wraps around.

transformer

val transformer: ColumnTransformer<Unwrapped, Wrapped>

Functions

equals

open operator override fun equals(other: Any?): Boolean

hashCode

open override fun hashCode(): Int

nonNullValueAsDefaultString

open fun nonNullValueAsDefaultString(value: Wrapped & Any): String

Returns the String representation of the specified non-null value when value is set as the default for the column.

nonNullValueToString

open fun nonNullValueToString(value: Wrapped & Any): String

Returns the SQL representation of the specified non-null value, for this column type.

notNullValueToDB

open override fun notNullValueToDB(value: Wrapped & Any): Any

Returns an object compatible with the database, from the specified non-null value, for this column type.

parameterMarker

open override fun parameterMarker(value: Wrapped?): String

Defines the appearance of parameter markers in prepared SQL statements.

readObject

open override fun readObject(rs: RowApi, index: Int): Any?

Returns the object at the specified index in the rs.

setParameter

open override fun setParameter(stmt: PreparedStatementApi, index: Int, value: Any?)

Sets the value at the specified index into the stmt.

sqlType

open override fun sqlType(): String

Returns the SQL type of this column.

toString

open override fun toString(): String

unwrapRecursive

open override fun unwrapRecursive(value: Wrapped?): Any?

Recursively unwraps the given value by applying the delegate's transformation.

validateValueBeforeUpdate

open fun validateValueBeforeUpdate(value: Wrapped?)

Function checks that provided value is suites the column type and throws IllegalArgumentException otherwise. value can be of any type (including Expression)

valueAsDefaultString

open fun valueAsDefaultString(value: Wrapped?): String

Returns the String representation of the specified value when value is set as the default for the column. If the value is null and the column is not nullable, an exception will be thrown. Used for metadata default value comparison.

valueFromDB

open override fun valueFromDB(value: Any): Wrapped?

Converts the specified value (from the database) to an object of the appropriated type, for this column type. Default implementation returns the same instance.

valueFromDBOrNull

fun valueFromDBOrNull(value: Any?): Wrapped

Transforms a value read from the database, handling null values by mapping them to a non-nullable Wrapped value via the transformer.

valueToDB

open override fun valueToDB(value: Wrapped?): Any?

Returns an object compatible with the database, from the specified value, for this column type.

valueToString

open override fun valueToString(value: Wrapped?): String

Returns the SQL representation of the specified value, for this column type. If the value is null and the column is not nullable, an exception will be thrown. Used when generating an SQL statement and when logging that statement.