Use ReactiveAdapterRegistry for return type checks

See gh-991

Author: rstoyanchev

spring-graphql/src/main/java/org/springframework/graphql/data/federation/FederationSchemaFactory.java

@@ -20,7 +20,6 @@
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.concurrent.CompletionStage;
 import java.util.function.BiFunction;
 import java.util.stream.Collectors;
 
@@ -31,13 +30,13 @@
 import graphql.schema.TypeResolver;
 import graphql.schema.idl.RuntimeWiring;
 import graphql.schema.idl.TypeDefinitionRegistry;
-import reactor.core.publisher.Flux;
-import reactor.core.publisher.Mono;
 
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.expression.BeanFactoryResolver;
 import org.springframework.core.KotlinDetector;
 import org.springframework.core.MethodParameter;
+import org.springframework.core.ReactiveAdapter;
+import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.graphql.data.GraphQlArgumentBinder;
 import org.springframework.graphql.data.method.HandlerMethod;
@@ -188,15 +187,16 @@ public SchemaTransformer createSchemaTransformer(TypeDefinitionRegistry registry
 	public record EntityMappingInfo(String typeName, HandlerMethod handlerMethod) {
 
 		public boolean isBatchHandlerMethod() {
-			MethodParameter type = handlerMethod().getReturnType();
-			Class<?> paramType = type.getParameterType();
-			if (Flux.class.isAssignableFrom(paramType)) {
-				return true;
+			MethodParameter returnType = handlerMethod().getReturnType();
+			Class<?> clazz = returnType.getParameterType();
+			ReactiveAdapter adapter = ReactiveAdapterRegistry.getSharedInstance().getAdapter(clazz);
+			if (adapter != null) {
+				if (adapter.isMultiValue()) {
+					return true;
+				}
+				returnType = returnType.nested();
 			}
-			if (Mono.class.isAssignableFrom(paramType) || CompletionStage.class.isAssignableFrom(paramType)) {
-				type = type.nested();
-			}
-			return List.class.isAssignableFrom(type.getParameterType());
+			return List.class.isAssignableFrom(returnType.getNestedParameterType());
 		}
 	}
 

spring-graphql/src/main/java/org/springframework/graphql/data/method/annotation/support/AnnotatedControllerConfigurer.java

@@ -45,13 +45,6 @@
 import graphql.schema.GraphQLCodeRegistry;
 import graphql.schema.idl.RuntimeWiring;
 import graphql.schema.idl.TypeDefinitionRegistry;
-import kotlin.jvm.JvmClassMappingKt;
-import kotlin.reflect.KFunction;
-import kotlin.reflect.KType;
-import kotlin.reflect.full.KClassifiers;
-import kotlin.reflect.full.KTypes;
-import kotlin.reflect.jvm.ReflectJvmMapping;
-import kotlinx.coroutines.flow.Flow;
 import org.dataloader.DataLoader;
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
@@ -64,6 +57,8 @@
 import org.springframework.core.KotlinDetector;
 import org.springframework.core.MethodParameter;
 import org.springframework.core.ParameterNameDiscoverer;
+import org.springframework.core.ReactiveAdapter;
+import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.data.domain.ScrollPosition;
@@ -384,15 +379,15 @@ private DataFetcher<Object> registerBatchLoader(DataFetcherMappingInfo info) {
 			clazz = returnType.getNestedParameterType();
 		}
 
-		if (clazz.equals(Flux.class) || Collection.class.isAssignableFrom(clazz) ||
-				(KotlinDetector.isSuspendingFunction(method) && KotlinDelegate.isFlowReturnType(method))) {
+		ReactiveAdapter adapter = ReactiveAdapterRegistry.getSharedInstance().getAdapter(clazz);
 
+		if (Collection.class.isAssignableFrom(clazz) || (adapter != null && adapter.isMultiValue())) {
 			registration.registerBatchLoader(invocable::invokeForIterable);
 			ResolvableType valueType = ResolvableType.forMethodParameter(returnType.nested());
 			return new BatchMappingDataFetcher(info, valueType, dataLoaderKey);
 		}
 
-		if (clazz.equals(Mono.class)) {
+		if (adapter != null) {
 			returnType = returnType.nested();
 			clazz = returnType.getNestedParameterType();
 		}
@@ -672,20 +667,4 @@ Set<DataFetcherMappingInfo> removeExplicitMappings(
 		}
 	}
 
-
-	/**
-	 * Inner class to avoid a hard dependency on Kotlin at runtime.
-	 */
-	private static final class KotlinDelegate {
-
-		private static final KType flowType =
-				KClassifiers.getStarProjectedType(JvmClassMappingKt.getKotlinClass(Flow.class));
-
-		static boolean isFlowReturnType(Method method) {
-			KFunction<?> function = ReflectJvmMapping.getKotlinFunction(method);
-			return (function != null && KTypes.isSubtypeOf(function.getReturnType(), flowType));
-		}
-
-	}
-
 }