dataloaderexample.java

       // a batch loader function that will be called with N or more keys for batch loading
       BatchLoader<String, Object> characterBatchLoader = new BatchLoader<String, Object>() {
           @Override
           public CompletionStage<List<Object>> load(List<String> keys) {
               //
               // we use supplyAsync() of values here for maximum parellisation
               //
               return CompletableFuture.supplyAsync(() -> getCharacterDataViaBatchHTTPApi(keys));
           }
       };
       // a data loader for characters that points to the character batch loader
       DataLoader characterDataLoader = new DataLoader<String, Object>(characterBatchLoader);
       //
       // use this data loader in the data fetchers associated with characters and put them into
       // the graphql schema (not shown)
       //
       DataFetcher heroDataFetcher = new DataFetcher() {
           @Override
           public Object get(DataFetchingEnvironment environment) {
               return characterDataLoader.load("2001"); // R2D2
           }
       };
       DataFetcher friendsDataFetcher = new DataFetcher() {
           @Override
           public Object get(DataFetchingEnvironment environment) {
               StarWarsCharacter starWarsCharacter = environment.getSource();
               List<String> friendIds = starWarsCharacter.getFriendIds();
               return characterDataLoader.loadMany(friendIds);
           }
       };
       //
       // DataLoaderRegistry is a place to register all data loaders in that needs to be dispatched together
       // in this case there is 1 but you can have many
       //
       DataLoaderRegistry registry = new DataLoaderRegistry();
       registry.register(characterDataLoader);
       //
       // this instrumentation implementation will dispatched all the dataloaders
       // as each level fo the graphql query is executed and hence make batched objects
       // available to the query and the associated DataFetchers
       //
       DataLoaderDispatcherInstrumentation dispatcherInstrumentation
               = new DataLoaderDispatcherInstrumentation(registry);
       //
       // now build your graphql object and execute queries on it.
       // the data loader will be invoked via the data fetchers on the
       // schema fields
       //
       GraphQL graphQL = GraphQL.newGraphQL(buildSchema())
               .instrumentation(dispatcherInstrumentation)
               .build();