Use reflection for JdkFlowAdapter

To avoid compiler issues on Eclipse.

Author: rstoyanchev

spring-core/src/main/java/org/springframework/core/ReactiveAdapterRegistry.java

@@ -280,22 +280,25 @@ void registerAdapters(ReactiveAdapterRegistry registry) {
 	private static class ReactorJdkFlowAdapterRegistrar {
 
 		void registerAdapter(ReactiveAdapterRegistry registry) throws Exception {
+
 			// TODO: remove reflection when build requires JDK 9+
-			Class<?> type = ClassUtils.forName("java.util.concurrent.Flow.Publisher", getClass().getClassLoader());
-			Method toFluxMethod = getMethod("flowPublisherToFlux", type);
-			Method toFlowMethod = getMethod("publisherToFlowPublisher", Publisher.class);
+
+			String publisherName = "java.util.concurrent.Flow.Publisher";
+			Class<?> publisherClass = ClassUtils.forName(publisherName, getClass().getClassLoader());
+
+			String adapterName = "reactor.adapter.JdkFlowAdapter";
+			Class<?> flowAdapterClass = ClassUtils.forName(adapterName,  getClass().getClassLoader());
+
+			Method toFluxMethod = flowAdapterClass.getMethod("flowPublisherToFlux", publisherClass);
+			Method toFlowMethod = flowAdapterClass.getMethod("publisherToFlowPublisher", Publisher.class);
 			Object emptyFlow = ReflectionUtils.invokeMethod(toFlowMethod, null, Flux.empty());
 
 			registry.registerReactiveType(
-					ReactiveTypeDescriptor.multiValue(type, () -> emptyFlow),
+					ReactiveTypeDescriptor.multiValue(publisherClass, () -> emptyFlow),
 					source -> (Publisher<?>) ReflectionUtils.invokeMethod(toFluxMethod, null, source),
 					publisher -> ReflectionUtils.invokeMethod(toFlowMethod, null, publisher)
 			);
 		}
-
-		private static Method getMethod(String name, Class<?> argumentType) throws NoSuchMethodException {
-			return reactor.adapter.JdkFlowAdapter.class.getMethod(name, argumentType);
-		}
 	}