On demand data loader registry

[etienne-sf]

Hello,

I'm building on the graphql-maven-plugin-project that is both a Maven and a Gradle plugin. It generates the code that allows to easily develop a java GraphQL client, or a GraphQL server (it just generated the code that allows to directly use graphql-java).

On server side, this plugin faces the issue that the DataLoader is loaded once. And so, the cache is global, and not per request.

This PR allows to have a per request dataloader cache.

Here are the updates contained in this PR:

• Add of a new OnDemandDataLoaderRegistry interface. This interface allows to provide a Spring Bean that can provide a new DataLoaderRegistry each time its getNewDataLoaderRegistry() method is called.
• Update of the DefaultGraphQLInvocation bean, so that when a OnDemandDataLoaderRegistry is provided, its getNewDataLoaderRegistry() method is called for each request invocation. This allows to have a per_request dataloader cache
• Add of unit test to check that.
• README updated, with a documentation about this.

Of course, these updates are for both the webmvc and the webflux modules.

I also added the javax.annotation-api dependency, as it is necessary to compile on my java version.

Etienne

[andimarek]

This project is now archived in favor of the official Spring GraphQL integration.