Plugins
Maven
A Maven plugin to support the OpenAPI generator project
Example
Add to your build->plugins section (default phase is generate-sources phase)
<plugin>
    <groupId>org.openapitools</groupId>
    <artifactId>openapi-generator-maven-plugin</artifactId>
    <version>3.3.4</version>
    <executions>
        <execution>
            <goals>
                <goal>generate</goal>
            </goals>
            <configuration>
                <inputSpec>${project.basedir}/src/main/resources/api.yaml</inputSpec>
                <generatorName>java</generatorName>
                <configOptions>
                   <sourceFolder>src/gen/java/main</sourceFolder>
                </configOptions>
            </configuration>
        </execution>
    </executions>
</plugin>
Followed by:
mvn clean compile
For full details of all options, see the plugin README.
Gradle
This gradle plugin offers a declarative DSL via extensions (these are Gradle project extensions). These map almost fully 1:1 with the options you’d pass to the CLI or Maven plugin. The plugin maps the extensions to a task of the same name to provide a clean API. If you’re interested in the extension/task mapping concept from a high-level, you can check out Gradle’s docs.
To include in your project, add the following to build.gradle:
buildscript {
  repositories {
    mavenLocal()
    mavenCentral()
  }
  dependencies {
    classpath "org.openapitools:openapi-generator-gradle-plugin:3.3.4"
  }
}
apply plugin: 'org.openapi.generator'
This gives access to the following tasks:
| Task | Description | 
|---|---|
| openApiGenerate | Generate code via Open API Tools Generator for Open API 2.0 or 3.x specification documents. | 
| openApiGenerators | Lists generators available via Open API Generators. | 
| openApiMeta | Generates a new generator to be consumed via Open API Generator. | 
| openApiValidate | Validates an Open API 2.0 or 3.x specification document. | 
The plugin implements the above tasks as project extensions of the same name. If you’d like to declare these tasks as dependencies to other tasks (using
dependsOn), you’ll need a task reference. e.g.:compileJava.dependsOn tasks.openApiGenerate
For full details of all options, see the plugin README.
Example
An example task for generating a kotlin client:
openApiGenerate {
    generatorName = "kotlin"
    inputSpec = "$rootDir/specs/petstore-v3.0.yaml".toString()
    outputDir = "$buildDir/generated".toString()
    apiPackage = "org.openapi.example.api"
    invokerPackage = "org.openapi.example.invoker"
    modelPackage = "org.openapi.example.model"
    modelFilesConstrainedTo = [
            "Error"
    ]
    configOptions = [
        dateLibrary: "java8"
    ]
}