Annotation Processing

Overview

Komapper uses the Kotlin Symbol Processing API (KSP) to process annotations in mapping definitions and generate the result as metamodel source code at compile-time.

To run KSP, you need to configure your Gradle build script as follows:

plugins {
  id("com.google.devtools.ksp") version "1.6.21-1.0.5"
  kotlin("jvm") version "1.6.21"
}

dependencies {
  val komapperVersion = "1.1.2"
  ksp("org.komapper:komapper-processor:$komapperVersion")
}

The komapper-processor module contains the KSP annotation processor.

After the above settings, running Gradle’s build task will generate code under the build/generated/ksp/main/kotlin directory.

Options

Options allow you to change the behavior of the annotation processor. There are four available options:

• komapper.prefix
• komapper.suffix
• komapper.enumStrategy
• komapper.namingStrategy
• komapper.metaObject

The options can be specified in the Gradle build script as follows:

ksp {
  arg("komapper.prefix", "")
  arg("komapper.suffix", "Metamodel")
  arg("komapper.enumStrategy", "ordinal")
  arg("komapper.namingStrategy", "UPPER_SNAKE_CASE")
  arg("komapper.metaObject", "example.Metamodels")
}

komapper.prefix

This option specifies the prefix for the simple name of generated metamodel class. The default value is _ (underscore).

komapper.suffix

This option specifies the suffix for the name of generated metamodel class. The default value is an empty string.

komapper.enumStrategy

This option specifies the strategy for how to map the enum properties to database columns. The value can be either name or ordinal. The default value is name.

Note that specification by @KomapperEnum takes precedence over this strategy.

The possible values for the komapper.enumStrategy option are defined as follows:

name

map the name property of Enum class to the string type column.

ordinal

map the ordinal property of Enum class to the integer type column.

komapper.namingStrategy

This option specifies the strategy for how to resolve database table and column names from Kotlin entity classes and properties.

The resolved names will be included in the generated metamodel code. Note that if a name is specified in @KomapperTable or @KomapperColumn, it takes precedence over the name determined by this strategy.

The possible values for the komapper.namingStrategy option are defined as follows:

implicit

This strategy converts nothing. Entity class and property names are used as-is as table and column names.

lower_snake_case

This strategy converts entity class and property names to snake_case and then to lowercase.

UPPER_SNAKE_CASE

This strategy converts entity class and property names to snake_case and then to UPPERCASE.

The default strategy is lower_snake_case.

komapper.metaObject

This option specifies the name of the object that provides metamodel instances as extension properties. Default is org.komapper.core.dsl.Meta.