Execution context

Kotlin functions may define an additional ExecutionContext parameter. This parameter is special and never exposed in GraphQL.

Kotlin	GraphQL
@GraphQLQuery class Query { fun viewer(context: ExecutionContext): User { // Do something with context return user } }	type Query { # this field has no arguments viewer: user }

ExecutionContext is a typesafe map inspired by CoroutinesContext. Define your own context by extending ExecutionContext.Element:

class CurrentUser(val id: String) : ExecutionContext.Element {
  override val key: ExecutionContext.Key<*>
    get() = Key

  companion object Key : ExecutionContext.Key<CurrentUser>
}

And pass it to ExecutableSchema.execute():

// Get the current logged-in user
val context = CurrentUser(getUserIdFromHttpHeaders())

val response = executableSchema.execute(
  GraphQLRequest.Builder()
    .document("{ viewer { name } }")
    .build(),
  context
)

CurrentUser is now available in Query.viewer:

class Query {
  fun viewer(context: ExecutionContext): User {
    val id = context[CurrentUser]!!.id
    return userById(id)
  }
}

Last modified: 16 July 2024