João Esperancinha Apollo 4 Kotlin Made me GraphQL 2024/11/12 

Gnothi seauton Know thyself What components make up this talk? 

What is GraphQL? ● Query Language ● Developed by Facebook 2015 ● Runtime Engine ● Exact data requests ● It is not REST ● One single endpoint 

● Overfetching and underfetching of data What does GraphQL solves? ● Multiple endpoints in general but particularly for the same resource ● Requirement Changes ● Lack of typed contracts ● Inconsistent and redundant API Documentation 

What is Apollo Kotlin? ● Complex Queries ● Efficient Data Fetching ● Client Flexibility ● Evolving APIs ● Spring GraphQL Integration 

What does Apollo Kotlin solve? ● Code generation ● Type-Safe Queries and Responses ● Optimized Caching and Offline Support ● Coroutines and Asynchronous Operations ● Flexible Networking Integration ● Error Handling ● Server-Side Usage ● Integration with Other Apollo Tools ● Efficient communication with GraphQL APIs 

What is Spring GraphQL? ● Efficient Data Fetching with Batch Loading ● Unified API endpoint ● Data Fetching Flexibility ● GraphQL Annotations ● Schema driven development ● GraphiQL and Testing ● Security and Access Control 

What does Spring GraphQL solve? ● Overfetching and underfetching of data ● Consolidates all APIs into a single endpoint ● Improving Data Fetching Efficiency ● Enforcing a Clear Schema for API Interactions ● Reducing Redundant API Calls 

What does Spring GraphQL solve? ● Real-Time Data with Subscriptions ● Enhanced Error Management and Validation ● Fine-Grained Access Control ● Developer Productivity with Tooling ● Smooth Integration with the Spring Ecosystem 

Kairos Know the right moment How does the system look like? 

No content

Meden agan Nothing in excess How to program it? 

Setting up the guitar-service ● spring-boot-starter-webflux - Make it reactive ● spring-boot-starter-graphql - Enable GraphQL ● kotlin-stdlib - Enable Kotlin ● kotlin-reflect - To enable necessary reflection features ● spring-data-commons - Required for the data structures ● kotlinx-coroutines-core - Required coroutine libraries ● kotlinx-coroutines-reactor - Reactive services engine 

Creating the guitar service type Query { guitarById(id: ID): GuitarDto ownerById(id: ID): OwnerDto } type GuitarDto { id: ID brand: String model: String year: Int owner: OwnerDto } type OwnerDto { id: ID firstName: String lastName: String } schema.graphqls - By default, this file is kept in the resources folder. Spring GraphQL knows to find it there 

Creating the guitar-service spring.graphql.graphiql.enabled=true spring.main.web-application-type=reactive application.properties @Controller class OwnerController( val ownerService: OwnerService ) { @QueryMapping suspend fun ownerById(@Argument("id") id: Long): OwnerDto? = ownerService.getByIdOrNull(id) } @Controller @QueryMapping @Argument GraphQL still follows the MVC pattern QueryMapping maps the method to the definition Argument maps the input argument of the method 

Creating the guitar-service spring.graphql.graphiql.enabled=true spring.main.web-application-type=reactive @Controller class GuitarController( val guitarService: GuitarService, val ownerService: OwnerService ) { @QueryMapping suspend fun guitarById(@Argument("id") id: Long) = guitarService.getByIdOrNull(id) @SchemaMapping suspend fun owner(guitarDto: GuitarDto): OwnerDto? = ownerService.getByIdOrNull(guitarDto.ownerId) } @SchemaMapping application.properties SchemaMapping maps parts of the parent object with its child objects 

GraphiQL - Interface http://localhost:8080/graphiql?path=/graphql 

Setting up the guitar-client ● In Gradle ● apollo-runtime - Enable runtime to create object ● com.apollographql.apollo - Configure apollo plugin 

apollo { service("service") { packageName.set("org.jesperancinha.guitar.gui") introspection { endpointUrl.set("http://localhost:8080/graphql") schemaFile.set(file("src/main/graphql/schema.graphqls")) } } } Setting up the guitar-client in Gradle packageName is the package name of the created classes endpointUrl is the address where we can find our graphql definition schemaFile is where we want the fetched definition to be saved to schemaFile packageName endpointUrl 

DEMO Time! 

Questions? I am an inquisitive cat 

Resources ● https://spring.io/guides/gs/graphql-server ● https://www.apollographql.com/docs/kotlin/tutorial/04-execute-the-query ● https://plugins.jetbrains.com/plugin/8097-graphql 

Source code https://github.com/jesperancinha/guitar-shop 

About me ● Homepage - https://joaofilipesabinoesperancinha.nl ● Threads - https://www.threads.net/@joaofisaes ● LinkedIn - https://www.linkedin.com/in/joaoesperancinha/ ● YouTube - https://www.youtube.com/@jesprotech ● Bluesky - https://bsky.app/profile/jesperancinha.bsky.social ● Mastodon - https://masto.ai/@jesperancinha ● GitHub - https://github.com/jesperancinha ● Hackernoon - https://hackernoon.com/u/jesperancinha ● DevTO - https://dev.to/jofisaes ● Medium - https://medium.com/@jofisaes 

Thank you! See you next time!