OpenAPI Ktor Client Generator

A powerful Gradle plugin that transforms OpenAPI v3 specifications into production-ready Kotlin Ktor client code. You can customize the generated clients and models to match your project's specific needs.

Prerequisites

• JDK 17+
• Gradle 9+

Installation

Add the plugin to your build.gradle.kts:

plugins {
    id("org.litote.openapi.ktor.client.generator.gradle") version "<last version>"
}

Where <last version> is

Configuration

Configure the plugin in your build.gradle.kts:

apiClientGenerator {
    generators {
        create("openapi") { // create a new task name: generateOpenapi
            outputDirectory = file("build/generated")
            openApiFile = file("src/main/openapi/openapi.json")
            basePackage = "com.example.api"
            // Optional: Add more configuration options below
        }
        // You can create multiple tasks with different names
    }
}

For a complete example with all available options, see e2e/build.gradle.kts.

Usage

Run the generation task directly:

./gradlew generateOpenapi

Or trigger generation as part of the build process:

./gradlew build

This will generate Ktor client code based on your OpenAPI specification and plugin configuration. The generated code will be placed in the configured outputDirectory.

Configuration Properties

Root properties

Property	Description	Default value	Allowed values
generators	Generators configuration	{}	Any configuration
skip	Skip all clients generation	false	Boolean

Generator properties

Property	Description	Default value	Allowed values
openApiFile	OpenAPI v3 source file	file("src/main/openapi/${name}.json")	Any existing OpenAPI file
outputDirectory	Target directory for generated sources (a src/main/kotlin subdirectory will be added)	file("build/api-${name}")	Any relative directory
basePackage	Base package for all generated classes	org.example	Any valid package name
allowedPaths	Restrict generation to a subset of OpenAPI paths	empty (all paths are generated)	Any subset of paths defined in the OpenAPI spec
modulesIds	Extra generation modules to enable	Empty (no modules)	UnknownEnumValueModule, LoggingSl4jModule
skip	Skip this client generation	false	Boolean

Troubleshooting

Gradle error: Implicit dependencies between tasks

If you get an error with this message, the generator tasks have implicit dependencies with other tasks. (see https://docs.gradle.org/current/userguide/validation_problems.html#implicit_dependency)

Add the dependencies explicitly in the gradle.kts file:

project
    .tasks
    .named { name ->
        //any condition to match the tasks names
        name.contains("whatever")
    }
    .configureEach {
        project.tasks.withType(org.litote.openapi.ktor.client.generator.plugin.GenerateTask::class.java).forEach {
            dependsOn(it) 
        }
    }

Linter errors

Generated code is not linted. Just ignore the errors by adding a .editorconfig file to your project, for example for ktlint:

[build/**/*]
ktlint = disabled