Part 1: GraphQL with Spring Boot, JPA and Kotlin

GraphQL is a query language for dynamic queries on linked data. In the GraphQL world, there are many tutorials and documentation that illustrate the concrete introduction to GraphQL. Since getting started requires a lot of explanation, regular tutorials usually have a simple setup, which does not reflect the real world complexity. If additional technologies are added or the complexity of the project increases, these “Hello World” examples are usually no longer so helpful.

This article introduces GraphQL on the technology Spring Boot with JPA and Kotlin. I also present some best practices which I have learned while I have worked with it. You can find the source code here: https://github.com/akquinet/kotlin-spring-graphql

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Java Optional and Kotlin Nullable

We are using Kotlin and Spring Boot in one of our projects. This includes Spring Boot Jpa Repositories. We are using a CrudRepository that provides basic functionalities like save(), delete(), findById() etc. This library is written in Java, hence method signatures look like this:

Optional<T> findById(ID var1); 

Using this API out of the box would force us to deal with cumbersome Java Optionals. Since we are implementing in Kotlin we would like to use Kotlin Nullables instead and as it turned out we can achieve this very easily.

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