Alternatives and detailed information of kobby

Kobby is a codegen plugin of Kotlin DSL Client by GraphQL schema. The generated DSL supports execution of complex GraphQL queries, mutations and subscriptions in Kotlin with syntax similar to native GraphQL syntax. Moreover, you can customize generated DSL by means of GraphQL schema directives and Kotlin extension functions.

Documentation

Kobby Documentation

Tutorials

Requirements

Gradle at least version 7.0 is required.
Maven at least version 3.6.3 is required.
Kotlin at least version 1.5 is required to compile generated client DSL.
1.5.0 <= Ktor version < 2.0.0 is required to generate default adapters.

Contributing

Please see CONTRIBUTING.md

Gradle

plugins {
    id("io.github.ermadmi78.kobby") version "1.6.0"
}

Maven

<build>
    <plugins>
        <plugin>
            <groupId>io.github.ermadmi78</groupId>
            <artifactId>kobby-maven-plugin</artifactId>
            <version>1.6.0</version>
            <executions>
                <execution>
                    <phase>generate-sources</phase>
                    <goals>
                        <goal>generate-kotlin</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

Define your GraphQL schema

Put your GraphQL schema file in the project resources with graphqls extension. For example, let define cinema.graphqls schema file and put it in src/main/resources/io/github/ermadmi78/kobby/cinema/api/

Configure Kobby Gradle plugin

Add Kobby plugin to your build.gradle.kts, to generate Kotlin DSL.
Configure Kotlin data types for scalars, defined in the GraphQL schema (more details about the scalar mapping see here).
Add Jackson dependency to generate Jackson annotations for DTO classes.
Add Kotlin plugin to your build.gradle.kts to compile generated DSL.

import io.github.ermadmi78.kobby.kobby

description = "Cinema API Example"

plugins {
    kotlin("jvm")
    `java-library`
    id("io.github.ermadmi78.kobby")
}

kobby {
    kotlin {
        scalars = mapOf(
            "Date" to typeOf("java.time", "LocalDate"),
            "JSON" to typeMap.parameterize(typeString, typeAny.nullable())
        )
    }
}

val jacksonVersion: String by project
dependencies {
    compileOnly("com.fasterxml.jackson.core:jackson-annotations:$jacksonVersion")
}

Generate Kotlin DSL Client by your GraphQL schema

Execute gradle build command to generate Kotlin DSL Client. The entry point of the DSL will be placed in the cinema.kt file (name of the DSL entry point file is the same as the name of GraphQL schema file):

More details about the entry point configuration see here.

Instantiate DSL Context

The cinema.kt file will contain the cinemaContextOf builder function, which creates instance of the CinemaContext interface - the entry point of the generated DSL. Note that the prefixes of the builder function, adapter and context interfaces are the same as the name of the GraphQL schema file.

fun cinemaContextOf(adapter: CinemaAdapter): CinemaContext = CinemaContextImpl(adapter)

More details about the DSL context see here

We have to pass instance of the CinemaAdapter interface to the cinemaContextOf function to create instance of the CinemaContext interface. By default, Kobby does not generate any adapter implementations. But we can ask Kobby to generate default Ktor implementations of the CinemaAdapter interface.

To do this just add io.ktor:ktor-client-cio dependency to you project:

val jacksonVersion: String by project
val ktorVersion: String by project
dependencies {
    // Add this dependency to enable Jackson annotation generation in DTO classes by Kobby
    compileOnly("com.fasterxml.jackson.core:jackson-annotations:$jacksonVersion")

    // Add this dependency to enable default Ktor adapters generation
    compileOnly("io.ktor:ktor-client-cio:$ktorVersion")
}

Rebuild the project, and Kobby will generate classes CinemaSimpleKtorAdapter and CinemaCompositeKtorAdapter in subpackage adapter.ktor. The prefix <Cinema> by default is the schema name.

The CinemaSimpleKtorAdapter is simple to configure, but it does not support GraphQL subscriptions - so we can use only queries and mutations:

val client = HttpClient {
    install(JsonFeature) {
        serializer = JacksonSerializer {
            registerModule(ParameterNamesModule(JsonCreator.Mode.PROPERTIES))
            registerModule(JavaTimeModule())
            // Force Jackson to serialize dates as String
            disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
        }
    }
}

val context = cinemaContextOf(CinemaSimpleKtorAdapter(client, "http://localhost:8080/graphql"))

The CinemaCompositeKtorAdapter is more difficult to configure, but it supports all types of GraphQL operations, including subscriptions:

val client = HttpClient {
    install(WebSockets)
}

val mapper = jacksonObjectMapper()
    .registerModule(ParameterNamesModule(JsonCreator.Mode.PROPERTIES))
    .registerModule(JavaTimeModule())
    // Force Jackson to serialize dates as String
    .disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)

val context = cinemaContextOf(
    CinemaCompositeKtorAdapter(
        client,
        "http://localhost:8080/graphql",
        "ws://localhost:8080/subscriptions",
        object : CinemaMapper {
            override fun serialize(value: Any): String =
                mapper.writeValueAsString(value)

            override fun <T : Any> deserialize(content: String, contentType: KClass<T>): T =
                mapper.readValue(content, contentType.java)
        }
    )
)

See here full example of adapters configuration. Note that you are not required to use the default adapters. You can write your own adapter implementation. For example, see here adapter implementation for Spring Boot integration tests.