GraphQL Kotlin Data Loader

Data Loaders are a popular caching pattern from the JavaScript GraphQL implementation.

Since graphql-java provides support for this pattern using the DataLoader and DataLoaderRegistry.

graphql-kotlin provides support for DataLoaders with this graphql-kotlin-dataloader module through common interfaces.

KotlinDataLoader

To help in the registration of DataLoaders, we have created a basic interface KotlinDataLoader:

interface KotlinDataLoader<K, V> {
    val dataLoaderName: String
    fun getDataLoader(graphQLContext: GraphQLContext): DataLoader<K, V>
}

This allows for library users to still have full control over the creation of the DataLoader and its various configuration options.

class UserDataLoader : KotlinDataLoader<ID, User> {
    override val dataLoaderName = "UserDataLoader"
    override fun getDataLoader(graphQLContext: GraphQLContext) =
        DataLoaderFactory.newDataLoader<ID, User>(
            { ids, batchLoaderEnvironment ->
                val context = batchLoaderEnvironment.getContext<GraphQLContext>()
                // do something with graphQLContext
                CompletableFuture.supplyAsync {
                    ids.map { id -> userService.getUser(id) }
                }
            },
            DataLoaderOptions.newOptions()
                .setCachingEnabled(false)
                .setBatchLoaderContextProvider { graphQLContext }
        )
}

KotlinDataLoaderRegistryFactory

Factory that facilitates the instantiation of a KotlinDataLoaderRegistry which is just a decorator of the original graphql-java DataLoaderRegistry. with the addition of allowing access to the state of the CacheMap (futures cache) of each DataLoader in order to know all futures state.

Install it

Using a JVM dependency manager, link graphql-kotlin-dataloader to your project.

With Maven:

<dependency>
  <groupId>com.expediagroup</groupId>
  <artifactId>graphql-kotlin-dataloader</artifactId>
  <version>${latestVersion}</version>
</dependency>

With Gradle (example using kts):

implementation("com.expediagroup:graphql-kotlin-dataloader:$latestVersion")

Use it

Use KotlinDataLoaderRegistryFactory

    val kotlinDataLoaderRegistry = KotlinDataLoaderRegistryFactory(
        UserDataLoader()
    ).generate(graphQLContext)

    val executionInput = ExecutionInput.newExecutionInput()
        .query("query MyAwesomeQuery { foo { bar } }")
        .dataLoaderRegistry(kotlinDataLoaderRegistry)
        .build()

    val result = graphQL.executeAsync(executionInput)

Documentation

Additional information can be found in our documentation and the Javadocs of all published library versions.

If you have a question about something you can not find in our documentation or javadocs, feel free to start a new discussion.