Most GraphQL libraries require developers to maintain two sources of truth for their GraphQL API: the schema and the corresponding code (data fetchers or resolvers, and types). Given the similarities between Kotlin and GraphQL, such as the ability to define nullable/non-nullable types, a schema can be generated from Kotlin code without any separate schema specification. graphql-kotlin builds upon graphql-java to allow code-only, or resolver-first, GraphQL services to be built.

For information on GraphQL, please visit the GraphQL website.

For information on graphql-java, please visit GraphQL Java.

Programming language: Kotlin
Tags: Web     Graphql     Api     Generator    
Latest version: v2.0.0-RC9.1

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GraphQL Kotlin

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GraphQL Kotlin is a collection of libraries built on top of graphql-java that aim to simplify running a GraphQL server in Kotlin

📦 Modules

⌨️ Usage

Below is a basic example of how graphql-kotlin-schema-generator converts your Kotlin code into a GraphQL schema. For more details, see our documentation below or in the individual module READMEs

data class Widget(val id: Int, val value: String)

class WidgetService {
  fun widgetById(id: Int): Widget? {
    // grabs widget from a data source, might return null

// Generate the schema
val config = SchemaGeneratorConfig(supportedPackages = listOf("org.example"))
val queries = listOf(TopLevelObject(WidgetService()))

toSchema(config, queries)

will generate

type Query {
  widgetById(id: Int!): Widget

type Widget {
  id: Int!
  value: String!

Then using graphql-kotlin-spring-server you can easily make your schema available as a GraphQL server with Spring Boot.

// Mark the class as a Spring GraphQL Query
class WidgetService : Query {
  fun widgetById(id: Int): Widget? {}

class Application

fun main(args: Array<String>) {

📋 Documentation

Examples and documentation are available on our documentation site hosted in GitHub Pages.

If you have a question about something you can not find in our documentation, the indivdual module READMEs, or javadocs, feel free to create an issue and tag it with the question label.

If you would like to contribute to our documentation see the website directory for more information.

👥 Contact

This project is part of Expedia Group Open Source but also maintained by a dedicated team

✏️ Contributing

To get started, please fork the repo and checkout a new branch. You can then build the library locally with Gradle

```shell script ./gradlew clean build

See more info in [CONTRIBUTING.md](CONTRIBUTING.md)

## ⚖️ License
This library is licensed under the [Apache License, Version 2.0](LICENSE)

*Note that all licence references and agreements mentioned in the GraphQL Kotlin README section above are relevant to that project's source code only.