---
title: Documentation for the kotlin Generator
---
## METADATA
| Property | Value | Notes |
| -------- | ----- | ----- |
| generator name | kotlin | pass this to the generate command after -g |
| generator stability | STABLE | |
| generator type | CLIENT | |
| generator language | Kotlin | |
| generator default templating engine | mustache | |
| helpTxt | Generates a Kotlin client. | |
## CONFIG OPTIONS
These options may be applied as additional-properties (cli) or configOptions (plugins). Refer to [configuration docs](https://openapi-generator.tech/docs/configuration) for more details.
| Option | Description | Values | Default |
| ------ | ----------- | ------ | ------- |
|additionalModelTypeAnnotations|Additional annotations for model type(class level annotations). List separated by semicolon(;) or new line (Linux or Windows)| |null|
|apiSuffix|suffix for api classes| |Api|
|artifactId|Generated artifact id (name of jar).| |kotlin-client|
|artifactVersion|Generated artifact's package version.| |1.0.0|
|collectionType|Option. Collection type to use|- **array**
- kotlin.Array
- **list**
- kotlin.collections.List
|list|
|dateLibrary|Option. Date library to use|- **threetenbp-localdatetime**
- Threetenbp - Backport of JSR310 (jvm only, for legacy app only)
- **kotlinx-datetime**
- kotlinx-datetime (preferred for multiplatform)
- **string**
- String
- **java8-localdatetime**
- Java 8 native JSR310 (jvm only, for legacy app only)
- **java8**
- Java 8 native JSR310 (jvm only, preferred for jdk 1.8+)
- **threetenbp**
- Threetenbp - Backport of JSR310 (jvm only, preferred for jdk < 1.8)
|java8|
|enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |original|
|failOnUnknownProperties|Fail Jackson de-serialization on unknown properties| |false|
|generateOneOfAnyOfWrappers|Generate oneOf, anyOf schemas as wrappers.| |false|
|generateRoomModels|Generate Android Room database models in addition to API models (JVM Volley library only)| |false|
|groupId|Generated artifact package's organization (i.e. maven groupId).| |org.openapitools|
|idea|Add IntellJ Idea plugin and mark Kotlin main and test folders as source folders.| |false|
|library|Library template (sub-template) to use|- **jvm-ktor**
- Platform: Java Virtual Machine. HTTP client: Ktor 1.6.7. JSON processing: Gson, Jackson (default).
- **jvm-okhttp4**
- [DEFAULT] Platform: Java Virtual Machine. HTTP client: OkHttp 4.2.0 (Android 5.0+ and Java 8+). JSON processing: Moshi 1.8.0.
- **jvm-spring-webclient**
- Platform: Java Virtual Machine. HTTP: Spring 5 (or 6 with useSpringBoot3 enabled) WebClient. JSON processing: Jackson.
- **jvm-spring-restclient**
- Platform: Java Virtual Machine. HTTP: Spring 6 RestClient. JSON processing: Jackson.
- **jvm-retrofit2**
- Platform: Java Virtual Machine. HTTP client: Retrofit 2.6.2.
- **multiplatform**
- Platform: Kotlin multiplatform. HTTP client: Ktor 1.6.7. JSON processing: Kotlinx Serialization: 1.2.1.
- **jvm-volley**
- Platform: JVM for Android. HTTP client: Volley 1.2.1. JSON processing: gson 2.8.9
- **jvm-vertx**
- Platform: Java Virtual Machine. HTTP client: Vert.x Web Client. JSON processing: Moshi, Gson or Jackson.
|jvm-okhttp4|
|mapFileBinaryToByteArray|Map File and Binary to ByteArray (default: false)| |false|
|modelMutable|Create mutable models| |false|
|moshiCodeGen|Whether to enable codegen with the Moshi library. Refer to the [official Moshi doc](https://github.com/square/moshi#codegen) for more info.| |false|
|nullableReturnType|Nullable return type| |false|
|omitGradlePluginVersions|Whether to declare Gradle plugin versions in build files.| |false|
|omitGradleWrapper|Whether to omit Gradle wrapper for creating a sub project.| |false|
|packageName|Generated artifact package name.| |org.openapitools.client|
|parcelizeModels|toggle "@Parcelize" for generated models| |null|
|requestDateConverter|JVM-Option. Defines in how to handle date-time objects that are used for a request (as query or parameter)|- **toJson**
- [DEFAULT] Date formatter option using a json converter.
- **toString**
- Use the 'toString'-method of the date-time object to retrieve the related string representation.
|toJson|
|serializableModel|boolean - toggle "implements Serializable" for generated models| |null|
|serializationLibrary|What serialization library to use: 'moshi' (default), or 'gson' or 'jackson' or 'kotlinx_serialization'| |moshi|
|sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |null|
|sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |null|
|sourceFolder|source folder for generated code| |src/main/kotlin|
|supportAndroidApiLevel25AndBelow|[WARNING] This flag will generate code that has a known security vulnerability. It uses `kotlin.io.createTempFile` instead of `java.nio.file.Files.createTempFile` in order to support Android API level 25 and bellow. For more info, please check the following links https://github.com/OpenAPITools/openapi-generator/security/advisories/GHSA-23x4-m842-fmwf, https://github.com/OpenAPITools/openapi-generator/pull/9284| |false|
|useCoroutines|Whether to use the Coroutines adapter with the retrofit2 library.| |false|
|useRxJava3|Whether to use the RxJava3 adapter with the retrofit2 library.| |false|
|useSettingsGradle|Whether the project uses settings.gradle.| |false|
|useSpringBoot3|Whether to use the Spring Boot 3 with the jvm-spring-webclient library.| |false|
## IMPORT MAPPING
| Type/Alias | Imports |
| ---------- | ------- |
|BigDecimal|java.math.BigDecimal|
|Date|java.time.LocalDate|
|DateTime|java.time.OffsetDateTime|
|File|java.io.File|
|LocalDate|java.time.LocalDate|
|LocalDateTime|java.time.LocalDateTime|
|LocalTime|java.time.LocalTime|
|Timestamp|java.sql.Timestamp|
|URI|java.net.URI|
|UUID|java.util.UUID|
## INSTANTIATION TYPES
| Type/Alias | Instantiated By |
| ---------- | --------------- |
|array|kotlin.collections.ArrayList|
|list|kotlin.collections.ArrayList|
|map|kotlin.collections.HashMap|
## LANGUAGE PRIMITIVES
- kotlin.Array
- kotlin.Boolean
- kotlin.Byte
- kotlin.ByteArray
- kotlin.Char
- kotlin.Double
- kotlin.Float
- kotlin.Int
- kotlin.Long
- kotlin.Short
- kotlin.String
- kotlin.collections.List
- kotlin.collections.Map
- kotlin.collections.MutableList
- kotlin.collections.MutableMap
- kotlin.collections.MutableSet
- kotlin.collections.Set
## RESERVED WORDS
- ApiResponse
- abstract
- actual
- annotation
- as
- break
- class
- companion
- const
- constructor
- continue
- contract
- crossinline
- data
- delegate
- do
- dynamic
- else
- enum
- expect
- external
- false
- field
- final
- finally
- for
- fun
- if
- import
- in
- infix
- init
- inline
- inner
- interface
- internal
- is
- it
- lateinit
- noinline
- null
- object
- open
- operator
- out
- override
- package
- param
- private
- property
- protected
- public
- receiver
- reified
- return
- sealed
- setparam
- super
- suspend
- tailrec
- this
- throw
- true
- try
- typealias
- typeof
- val
- value
- var
- vararg
- when
- where
- while
## FEATURE SET
### Client Modification Feature
| Name | Supported | Defined By |
| ---- | --------- | ---------- |
|BasePath|✓|ToolingExtension
|Authorizations|✗|ToolingExtension
|UserAgent|✗|ToolingExtension
|MockServer|✗|ToolingExtension
### Data Type Feature
| Name | Supported | Defined By |
| ---- | --------- | ---------- |
|Custom|✗|OAS2,OAS3
|Int32|✓|OAS2,OAS3
|Int64|✓|OAS2,OAS3
|Float|✓|OAS2,OAS3
|Double|✓|OAS2,OAS3
|Decimal|✓|ToolingExtension
|String|✓|OAS2,OAS3
|Byte|✓|OAS2,OAS3
|Binary|✓|OAS2,OAS3
|Boolean|✓|OAS2,OAS3
|Date|✓|OAS2,OAS3
|DateTime|✓|OAS2,OAS3
|Password|✓|OAS2,OAS3
|File|✓|OAS2
|Uuid|✗|
|Array|✓|OAS2,OAS3
|Null|✗|OAS3
|AnyType|✗|OAS2,OAS3
|Object|✓|OAS2,OAS3
|Maps|✓|ToolingExtension
|CollectionFormat|✓|OAS2
|CollectionFormatMulti|✓|OAS2
|Enum|✓|OAS2,OAS3
|ArrayOfEnum|✓|ToolingExtension
|ArrayOfModel|✓|ToolingExtension
|ArrayOfCollectionOfPrimitives|✓|ToolingExtension
|ArrayOfCollectionOfModel|✓|ToolingExtension
|ArrayOfCollectionOfEnum|✓|ToolingExtension
|MapOfEnum|✓|ToolingExtension
|MapOfModel|✓|ToolingExtension
|MapOfCollectionOfPrimitives|✓|ToolingExtension
|MapOfCollectionOfModel|✓|ToolingExtension
|MapOfCollectionOfEnum|✓|ToolingExtension
### Documentation Feature
| Name | Supported | Defined By |
| ---- | --------- | ---------- |
|Readme|✓|ToolingExtension
|Model|✓|ToolingExtension
|Api|✓|ToolingExtension
### Global Feature
| Name | Supported | Defined By |
| ---- | --------- | ---------- |
|Host|✓|OAS2,OAS3
|BasePath|✓|OAS2,OAS3
|Info|✓|OAS2,OAS3
|Schemes|✗|OAS2,OAS3
|PartialSchemes|✓|OAS2,OAS3
|Consumes|✓|OAS2
|Produces|✓|OAS2
|ExternalDocumentation|✓|OAS2,OAS3
|Examples|✓|OAS2,OAS3
|XMLStructureDefinitions|✗|OAS2,OAS3
|MultiServer|✗|OAS3
|ParameterizedServer|✗|OAS3
|ParameterStyling|✗|OAS3
|Callbacks|✗|OAS3
|LinkObjects|✗|OAS3
### Parameter Feature
| Name | Supported | Defined By |
| ---- | --------- | ---------- |
|Path|✓|OAS2,OAS3
|Query|✓|OAS2,OAS3
|Header|✓|OAS2,OAS3
|Body|✓|OAS2
|FormUnencoded|✓|OAS2
|FormMultipart|✓|OAS2
|Cookie|✗|OAS3
### Schema Support Feature
| Name | Supported | Defined By |
| ---- | --------- | ---------- |
|Simple|✓|OAS2,OAS3
|Composite|✓|OAS2,OAS3
|Polymorphism|✗|OAS2,OAS3
|Union|✗|OAS3
|allOf|✗|OAS2,OAS3
|anyOf|✗|OAS3
|oneOf|✗|OAS3
|not|✗|OAS3
### Security Feature
| Name | Supported | Defined By |
| ---- | --------- | ---------- |
|BasicAuth|✓|OAS2,OAS3
|ApiKey|✓|OAS2,OAS3
|OpenIDConnect|✗|OAS3
|BearerToken|✓|OAS3
|OAuth2_Implicit|✓|OAS2,OAS3
|OAuth2_Password|✗|OAS2,OAS3
|OAuth2_ClientCredentials|✗|OAS2,OAS3
|OAuth2_AuthorizationCode|✓|OAS2,OAS3
|SignatureAuth|✗|OAS3
|AWSV4Signature|✗|ToolingExtension
### Wire Format Feature
| Name | Supported | Defined By |
| ---- | --------- | ---------- |
|JSON|✓|OAS2,OAS3
|XML|✗|OAS2,OAS3
|PROTOBUF|✗|ToolingExtension
|Custom|✗|OAS2,OAS3