Polish ReactiveAdapterRegistry

Issue: SPR-14902

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

@@ -67,99 +67,81 @@ public class ReactiveAdapterRegistry {
 
 		// Flux and Mono ahead of Publisher...
 
-		registerMonoAdapter(Mono.class,
-				source -> (Mono<?>) source, source -> source,
-				ReactiveTypeDescriptor.singleOptionalValue(Mono.class));
+		registerReactiveType(
+				ReactiveTypeDescriptor.singleOptionalValue(Mono.class),
+				source -> (Mono<?>) source,
+				source -> source
+		);
 
-		registerFluxAdapter(Flux.class,
-				source -> (Flux<?>) source, source -> source);
+		registerReactiveType(ReactiveTypeDescriptor.multiValue(Flux.class),
+				source -> (Flux<?>) source,
+				source -> source);
 
-		registerFluxAdapter(Publisher.class,
-				source -> Flux.from((Publisher<?>) source), source -> source);
+		registerReactiveType(ReactiveTypeDescriptor.multiValue(Publisher.class),
+				source -> Flux.from((Publisher<?>) source),
+				source -> source);
 
-		registerMonoAdapter(CompletableFuture.class,
-				source -> Mono.fromFuture((CompletableFuture<?>) source), Mono::toFuture,
-				ReactiveTypeDescriptor.singleOptionalValue(CompletableFuture.class)
+		registerReactiveType(
+				ReactiveTypeDescriptor.singleOptionalValue(CompletableFuture.class),
+				source -> Mono.fromFuture((CompletableFuture<?>) source),
+				source -> Mono.from(source).toFuture()
 		);
 
 		if (rxJava1Present && rxJava1Adapter) {
-			new RxJava1AdapterRegistrar().register(this);
+			new RxJava1Registrar().registerAdapters(this);
 		}
 		if (rxJava2Present) {
-			new RxJava2AdapterRegistrar().register(this);
+			new RxJava2Registrar().registerAdapters(this);
 		}
 	}
 
 
 	/**
-	 * Register an adapter for adapting to and from a {@link Mono}.
-	 * <p>The provided functions can assume that input will never be {@code null}
-	 * and also that any {@link Optional} wrapper is unwrapped.
+	 * Register a reactive type along with functions to adapt to and from a
+		 * Reactive Streams {@link Publisher}. The functions can assume their
+	 * input is never be {@code null} nor {@link Optional}.
 	 */
-	public void registerMonoAdapter(Class<?> reactiveType, Function<Object, Mono<?>> toAdapter,
-			Function<Mono<?>, Object> fromAdapter, ReactiveTypeDescriptor descriptor) {
-
-		this.adapters.add(new MonoReactiveAdapter(toAdapter, fromAdapter, descriptor));
-	}
+	public void registerReactiveType(ReactiveTypeDescriptor descriptor,
+			Function<Object, Publisher<?>> toAdapter, Function<Publisher<?>, Object> fromAdapter) {
 
-	/**
-	 * Register an adapter for adapting to and from a {@link Flux}.
-	 * <p>The provided functions can assume that input will never be {@code null}
-	 * and also that any {@link Optional} wrapper is unwrapped.
-	 */
-	public void registerFluxAdapter(Class<?> reactiveType, Function<Object, Flux<?>> toAdapter,
-			Function<Flux<?>, Object> fromAdapter) {
+		ReactiveAdapter adapter = (descriptor.isMultiValue() ?
+				new FluxReactiveAdapter(toAdapter, fromAdapter, descriptor) :
+				new MonoReactiveAdapter(toAdapter, fromAdapter, descriptor));
 
-		this.adapters.add(new FluxReactiveAdapter(toAdapter, fromAdapter,
-				ReactiveTypeDescriptor.multiValue(reactiveType)));
+		this.adapters.add(adapter);
 	}
 
-
 	/**
-	 * Get the adapter for the given reactive type to adapt from.
+	 * Get the adapter to use to adapt from the given reactive type.
 	 */
 	public ReactiveAdapter getAdapterFrom(Class<?> reactiveType) {
 		return getAdapterFrom(reactiveType, null);
 	}
 
 	/**
-	 * Get the adapter for the given reactive type to adapt from.
-	 * If the instance is not {@code null} its actual type is used to check.
+	 * Get the adapter to use to adapt from the given reactive type. Or if the
+	 * "source" object is not {@code null} its actual type is used instead.
 	 */
-	public ReactiveAdapter getAdapterFrom(Class<?> reactiveType, Object adaptee) {
-		Class<?> actualType = getActualType(reactiveType, adaptee);
-		return getAdapterInternal(supportedType -> supportedType.isAssignableFrom(actualType));
+	public ReactiveAdapter getAdapterFrom(Class<?> reactiveType, Object source) {
+		source = unwrapOptional(source);
+		Class<?> clazz = (source != null ? source.getClass() : reactiveType);
+		return getAdapter(type -> type.isAssignableFrom(clazz));
 	}
 
 	/**
 	 * Get the adapter for the given reactive type to adapt to.
 	 */
 	public ReactiveAdapter getAdapterTo(Class<?> reactiveType) {
-		return getAdapterTo(reactiveType, null);
+		return getAdapter(reactiveType::equals);
 	}
 
-	/**
-	 * Get the adapter for the given reactive type to adapt to.
-	 * If the instance is not {@code null} its actual type is used to check.
-	 */
-	public ReactiveAdapter getAdapterTo(Class<?> reactiveType, Object adaptee) {
-		Class<?> actualType = getActualType(reactiveType, adaptee);
-		return getAdapterInternal(supportedType -> supportedType.equals(actualType));
-	}
-
-	private ReactiveAdapter getAdapterInternal(Predicate<Class<?>> predicate) {
+	private ReactiveAdapter getAdapter(Predicate<Class<?>> predicate) {
 		return this.adapters.stream()
 				.filter(adapter -> predicate.test(adapter.getDescriptor().getReactiveType()))
 				.findFirst()
 				.orElse(null);
 	}
 
-
-	private static Class<?> getActualType(Class<?> reactiveType, Object adaptee) {
-		adaptee = unwrapOptional(adaptee);
-		return (adaptee != null ? adaptee.getClass() : reactiveType);
-	}
-
 	private static Object unwrapOptional(Object value) {
 		return (value instanceof Optional ? ((Optional<?>) value).orElse(null) : value);
 	}
@@ -168,14 +150,14 @@ public class ReactiveAdapterRegistry {
 	@SuppressWarnings("unchecked")
 	private static class MonoReactiveAdapter implements ReactiveAdapter {
 
-		private final Function<Object, Mono<?>> toAdapter;
+		private final Function<Object, Publisher<?>> toAdapter;
 
-		private final Function<Mono<?>, Object> fromAdapter;
+		private final Function<Publisher<?>, Object> fromAdapter;
 
 		private final ReactiveTypeDescriptor descriptor;
 
 
-		MonoReactiveAdapter(Function<Object, Mono<?>> to, Function<Mono<?>, Object> from,
+		MonoReactiveAdapter(Function<Object, Publisher<?>> to, Function<Publisher<?>, Object> from,
 				ReactiveTypeDescriptor descriptor) {
 
 			this.toAdapter = to;
@@ -194,7 +176,7 @@ public class ReactiveAdapterRegistry {
 			if (source == null) {
 				return Mono.empty();
 			}
-			return (Mono<T>) this.toAdapter.apply(source);
+			return (Mono<T>) Mono.from(this.toAdapter.apply(source));
 		}
 
 		@Override
@@ -203,7 +185,7 @@ public class ReactiveAdapterRegistry {
 			if (source == null) {
 				return Flux.empty();
 			}
-			return (Flux<T>) this.toMono(source).flux();
+			return (Flux<T>) toMono(source).flux();
 		}
 
 		@Override
@@ -213,21 +195,21 @@ public class ReactiveAdapterRegistry {
 
 		@Override
 		public Object fromPublisher(Publisher<?> source) {
-			return (source != null ? this.fromAdapter.apply((Mono<?>) source) : null);
+			return (source != null ? this.fromAdapter.apply(source) : null);
 		}
 	}
 
 	@SuppressWarnings("unchecked")
 	private static class FluxReactiveAdapter implements ReactiveAdapter {
 
-		private final Function<Object, Flux<?>> toAdapter;
+		private final Function<Object, Publisher<?>> toAdapter;
 
-		private final Function<Flux<?>, Object> fromAdapter;
+		private final Function<Publisher<?>, Object> fromAdapter;
 
 		private final ReactiveTypeDescriptor descriptor;
 
 
-		FluxReactiveAdapter(Function<Object, Flux<?>> to, Function<Flux<?>, Object> from,
+		FluxReactiveAdapter(Function<Object, Publisher<?>> to, Function<Publisher<?>, Object> from,
 				ReactiveTypeDescriptor descriptor) {
 
 			this.descriptor = descriptor;
@@ -246,7 +228,7 @@ public class ReactiveAdapterRegistry {
 			if (source == null) {
 				return Mono.empty();
 			}
-			return (Mono<T>) this.toAdapter.apply(source).next();
+			return (Mono<T>) toFlux(source).next();
 		}
 
 		@Override
@@ -255,7 +237,7 @@ public class ReactiveAdapterRegistry {
 			if (source == null) {
 				return Flux.empty();
 			}
-			return (Flux<T>) this.toAdapter.apply(source);
+			return (Flux<T>) Flux.from(this.toAdapter.apply(source));
 		}
 
 		@Override
@@ -265,56 +247,59 @@ public class ReactiveAdapterRegistry {
 
 		@Override
 		public Object fromPublisher(Publisher<?> source) {
-			return (source != null ? this.fromAdapter.apply((Flux<?>) source) : null);
+			return (source != null ? this.fromAdapter.apply(source) : null);
 		}
 	}
 
 
-	private static class RxJava1AdapterRegistrar {
+	private static class RxJava1Registrar {
 
-		public void register(ReactiveAdapterRegistry registry) {
-			registry.registerFluxAdapter(rx.Observable.class,
+		public void registerAdapters(ReactiveAdapterRegistry registry) {
+			registry.registerReactiveType(
+					ReactiveTypeDescriptor.multiValue(rx.Observable.class),
 					source -> Flux.from(RxReactiveStreams.toPublisher((rx.Observable<?>) source)),
 					RxReactiveStreams::toObservable
 			);
-			registry.registerMonoAdapter(rx.Single.class,
+			registry.registerReactiveType(
+					ReactiveTypeDescriptor.singleRequiredValue(rx.Single.class),
 					source -> Mono.from(RxReactiveStreams.toPublisher((rx.Single<?>) source)),
-					RxReactiveStreams::toSingle,
-					ReactiveTypeDescriptor.singleRequiredValue(rx.Single.class)
+					RxReactiveStreams::toSingle
 			);
-			registry.registerMonoAdapter(rx.Completable.class,
+			registry.registerReactiveType(
+					ReactiveTypeDescriptor.noValue(rx.Completable.class),
 					source -> Mono.from(RxReactiveStreams.toPublisher((rx.Completable) source)),
-					RxReactiveStreams::toCompletable,
-					ReactiveTypeDescriptor.noValue(rx.Completable.class)
+					RxReactiveStreams::toCompletable
 			);
 		}
 	}
 
-	private static class RxJava2AdapterRegistrar {
+	private static class RxJava2Registrar {
 
-		public void register(ReactiveAdapterRegistry registry) {
-			registry.registerFluxAdapter(Flowable.class,
+		public void registerAdapters(ReactiveAdapterRegistry registry) {
+			registry.registerReactiveType(
+					ReactiveTypeDescriptor.multiValue(Flowable.class),
 					source -> Flux.from((Flowable<?>) source),
 					source-> Flowable.fromPublisher(source)
 			);
-			registry.registerFluxAdapter(io.reactivex.Observable.class,
+			registry.registerReactiveType(
+					ReactiveTypeDescriptor.multiValue(io.reactivex.Observable.class),
 					source -> Flux.from(((io.reactivex.Observable<?>) source).toFlowable(BackpressureStrategy.BUFFER)),
 					source -> Flowable.fromPublisher(source).toObservable()
 			);
-			registry.registerMonoAdapter(io.reactivex.Single.class,
+			registry.registerReactiveType(
+					ReactiveTypeDescriptor.singleRequiredValue(io.reactivex.Single.class),
 					source -> Mono.from(((io.reactivex.Single<?>) source).toFlowable()),
-					source -> Flowable.fromPublisher(source).toObservable().singleElement().toSingle(),
-					ReactiveTypeDescriptor.singleRequiredValue(io.reactivex.Single.class)
+					source -> Flowable.fromPublisher(source).toObservable().singleElement().toSingle()
 			);
-			registry.registerMonoAdapter(Maybe.class,
+			registry.registerReactiveType(
+					ReactiveTypeDescriptor.singleOptionalValue(Maybe.class),
 					source -> Mono.from(((Maybe<?>) source).toFlowable()),
-					source -> Flowable.fromPublisher(source).toObservable().singleElement(),
-					ReactiveTypeDescriptor.singleOptionalValue(Maybe.class)
+					source -> Flowable.fromPublisher(source).toObservable().singleElement()
 			);
-			registry.registerMonoAdapter(io.reactivex.Completable.class,
+			registry.registerReactiveType(
+					ReactiveTypeDescriptor.noValue(io.reactivex.Completable.class),
 					source -> Mono.from(((io.reactivex.Completable) source).toFlowable()),
-					source -> Flowable.fromPublisher(source).toObservable().ignoreElements(),
-					ReactiveTypeDescriptor.noValue(io.reactivex.Completable.class)
+					source -> Flowable.fromPublisher(source).toObservable().ignoreElements()
 			);
 		}
 	}

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

@@ -85,6 +85,23 @@ public class ReactiveTypeDescriptor {
 	}
 
 
+	@Override
+	public boolean equals(Object other) {
+		if (this == other) {
+			return true;
+		}
+		if (other == null || getClass() != other.getClass()) {
+			return false;
+		}
+		return this.reactiveType.equals(((ReactiveTypeDescriptor) other).reactiveType);
+	}
+
+	@Override
+	public int hashCode() {
+		return this.reactiveType.hashCode();
+	}
+
+
 	/**
 	 * Descriptor for a reactive type that can produce 0..N values.
 	 */