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 "2.0.20-1.0.25"
  kotlin("jvm") version "2.0.20"
}

dependencies {
  val komapperVersion = "3.0.0"
  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. Available options are as follows:

• komapper.prefix
• komapper.suffix
• komapper.enumStrategy
• komapper.namingStrategy
• komapper.metaObject
• komapper.alwaysQuote
• komapper.enableEntityMetamodelListing
• komapper.enableEntityStoreContext
• komapper.enableEntityProjection

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")
  arg("komapper.alwaysQuote", "true")
  arg("komapper.enableEntityMetamodelListing", "true")
  arg("komapper.enableEntityStoreContext", "true")
  arg("komapper.enableEntityProjection", "true")
}

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.

type

map the Enum class to the enum type column. Note that a user-defined data type corresponding to the Enum class is required.

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. The default value is org.komapper.core.dsl.Meta.

komapper.alwaysQuote

This option indicates whether to quote table or column names in SQL statements. The default value is flase.

komapper.enableEntityMetamodelListing

This option indicates whether a list of entity metamodels should be available. The default value is flase.

If you set this option to true, you can get the list in the following ways:

val metamodels: List<EntityMetamodel<*, *, *>> = Meta.all()

val metamodels: List<EntityMetamodel<*, *, *>> = EntityMetamodels.list(Meta)

komapper.enableEntityStoreContext

Whether to enable the EntityStore context. The default value is false.

If this option is set to true, the Komapper`s annotation processor will generate code for the Association API that uses the context receiver.

See also Navigation code using context receiver.

tasks {
    withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile>().configureEach {
        kotlinOptions.freeCompilerArgs += listOf("-Xcontext-receivers")
    }
}

komapper.enableEntityProjection

This setting determines whether to enable the projection of query results into entities. When enabled, extension functions for both SelectQuery and TemplateSelectQueryBuilder are generated for all entity classes. The default value is false.

The name of the extension function will be formed as selectAs + the simple name of the entity class, like selectAsAddress.

If you want to change the name of the extension function or enable projection only for specific entity classes, please use the @KomapperProjection annotation.