Streamline ReactiveAdapterRegistry.getAdapter usage

Closes gh-22842

Author: jhoeller

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -118,13 +118,10 @@ else if (Collection.class.isAssignableFrom(parameter.getParameterType())) {
 		}
 		else {
 			valueClass = parameter.getParameterType();
-			ReactiveAdapterRegistry reactiveAdapterRegistry = ReactiveAdapterRegistry.getSharedInstance();
-			if (reactiveAdapterRegistry.hasAdapters()) {
-				ReactiveAdapter adapter = reactiveAdapterRegistry.getAdapter(valueClass);
-				if (adapter != null && !adapter.getDescriptor().isNoValue()) {
-					reactiveSuffix = ClassUtils.getShortName(valueClass);
-					valueClass = parameter.nested().getNestedParameterType();
-				}
+			ReactiveAdapter adapter = ReactiveAdapterRegistry.getSharedInstance().getAdapter(valueClass);
+			if (adapter != null && !adapter.getDescriptor().isNoValue()) {
+				reactiveSuffix = ClassUtils.getShortName(valueClass);
+				valueClass = parameter.nested().getNestedParameterType();
 			}
 		}
 
@@ -207,13 +204,10 @@ else if (Collection.class.isAssignableFrom(resolvedType)) {
 		}
 		else {
 			valueClass = resolvedType;
-			ReactiveAdapterRegistry reactiveAdapterRegistry = ReactiveAdapterRegistry.getSharedInstance();
-			if (reactiveAdapterRegistry.hasAdapters()) {
-				ReactiveAdapter adapter = reactiveAdapterRegistry.getAdapter(valueClass);
-				if (adapter != null && !adapter.getDescriptor().isNoValue()) {
-					reactiveSuffix = ClassUtils.getShortName(valueClass);
-					valueClass = ResolvableType.forMethodReturnType(method).getGeneric().toClass();
-				}
+			ReactiveAdapter adapter = ReactiveAdapterRegistry.getSharedInstance().getAdapter(valueClass);
+			if (adapter != null && !adapter.getDescriptor().isNoValue()) {
+				reactiveSuffix = ClassUtils.getShortName(valueClass);
+				valueClass = ResolvableType.forMethodReturnType(method).getGeneric().toClass();
 			}
 		}
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -41,7 +41,7 @@
  *
  * <p>By default, depending on classpath availability, adapters are registered
  * for Reactor, RxJava 1, RxJava 2 types, {@link CompletableFuture}, and Java 9+
- * Flow.Publisher.
+ * {@code Flow.Publisher}.
  *
  * @author Rossen Stoyanchev
  * @author Sebastien Deleuze
@@ -54,15 +54,14 @@ public class ReactiveAdapterRegistry {
 
 	private final boolean reactorPresent;
 
-	private final List<ReactiveAdapter> adapters = new ArrayList<>(32);
+	private final List<ReactiveAdapter> adapters = new ArrayList<>();
 
 
 	/**
 	 * Create a registry and auto-register default adapters.
 	 * @see #getSharedInstance()
 	 */
 	public ReactiveAdapterRegistry() {
-
 		ClassLoader classLoader = ReactiveAdapterRegistry.class.getClassLoader();
 
 		// Reactor
@@ -104,8 +103,8 @@ public boolean hasAdapters() {
 
 	/**
 	 * 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}.
+	 * Reactive Streams {@link Publisher}. The function arguments assume that
+	 * their input is neither {@code null} nor {@link Optional}.
 	 */
 	public void registerReactiveType(ReactiveTypeDescriptor descriptor,
 			Function<Object, Publisher<?>> toAdapter, Function<Publisher<?>, Object> fromAdapter) {
@@ -120,6 +119,7 @@ public void registerReactiveType(ReactiveTypeDescriptor descriptor,
 
 	/**
 	 * Get the adapter for the given reactive type.
+	 * @return the corresponding adapter, or {@code null} if none available
 	 */
 	@Nullable
 	public ReactiveAdapter getAdapter(Class<?> reactiveType) {
@@ -133,34 +133,41 @@ public ReactiveAdapter getAdapter(Class<?> reactiveType) {
 	 * (may be {@code null} if a concrete source object is given)
 	 * @param source an instance of the reactive type
 	 * (i.e. to adapt from; may be {@code null} if the reactive type is specified)
+	 * @return the corresponding adapter, or {@code null} if none available
 	 */
 	@Nullable
 	public ReactiveAdapter getAdapter(@Nullable Class<?> reactiveType, @Nullable Object source) {
+		if (this.adapters.isEmpty()) {
+			return null;
+		}
+
 		Object sourceToUse = (source instanceof Optional ? ((Optional<?>) source).orElse(null) : source);
 		Class<?> clazz = (sourceToUse != null ? sourceToUse.getClass() : reactiveType);
 		if (clazz == null) {
 			return null;
 		}
-
-		return this.adapters.stream()
-				.filter(adapter -> adapter.getReactiveType() == clazz)
-				.findFirst()
-				.orElseGet(() ->
-						this.adapters.stream()
-								.filter(adapter -> adapter.getReactiveType().isAssignableFrom(clazz))
-								.findFirst()
-								.orElse(null));
+		for (ReactiveAdapter adapter : this.adapters) {
+			if (adapter.getReactiveType() == clazz) {
+				return adapter;
+			}
+		}
+		for (ReactiveAdapter adapter : this.adapters) {
+			if (adapter.getReactiveType().isAssignableFrom(clazz)) {
+				return adapter;
+			}
+		}
+		return null;
 	}
 
 
 	/**
-	 * Return a shared default {@code ReactiveAdapterRegistry} instance, lazily
-	 * building it once needed.
+	 * Return a shared default {@code ReactiveAdapterRegistry} instance,
+	 * lazily building it once needed.
 	 * <p><b>NOTE:</b> We highly recommend passing a long-lived, pre-configured
 	 * {@code ReactiveAdapterRegistry} instance for customization purposes.
 	 * This accessor is only meant as a fallback for code paths that want to
 	 * fall back on a default instance if one isn't provided.
-	 * @return the shared {@code ReactiveAdapterRegistry} instance (never {@code null})
+	 * @return the shared {@code ReactiveAdapterRegistry} instance
 	 * @since 5.0.2
 	 */
 	public static ReactiveAdapterRegistry getSharedInstance() {

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ReactiveTypeHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -76,14 +76,14 @@ class ReactiveTypeHandler {
 
 	private static Log logger = LogFactory.getLog(ReactiveTypeHandler.class);
 
-	private final ReactiveAdapterRegistry reactiveRegistry;
+	private final ReactiveAdapterRegistry adapterRegistry;
 
 	private final TaskExecutor taskExecutor;
 
-	private Boolean taskExecutorWarning;
-
 	private final ContentNegotiationManager contentNegotiationManager;
 
+	private boolean taskExecutorWarning;
+
 
 	public ReactiveTypeHandler() {
 		this(ReactiveAdapterRegistry.getSharedInstance(), new SyncTaskExecutor(), new ContentNegotiationManager());
@@ -93,18 +93,20 @@ public ReactiveTypeHandler() {
 		Assert.notNull(registry, "ReactiveAdapterRegistry is required");
 		Assert.notNull(executor, "TaskExecutor is required");
 		Assert.notNull(manager, "ContentNegotiationManager is required");
-		this.reactiveRegistry = registry;
+		this.adapterRegistry = registry;
 		this.taskExecutor = executor;
-		this.taskExecutorWarning = executor instanceof SimpleAsyncTaskExecutor || executor instanceof SyncTaskExecutor;
 		this.contentNegotiationManager = manager;
+
+		this.taskExecutorWarning =
+				(executor instanceof SimpleAsyncTaskExecutor || executor instanceof SyncTaskExecutor);
 	}
 
 
 	/**
 	 * Whether the type can be adapted to a Reactive Streams {@link Publisher}.
 	 */
 	public boolean isReactiveType(Class<?> type) {
-		return (this.reactiveRegistry.hasAdapters() && this.reactiveRegistry.getAdapter(type) != null);
+		return (this.adapterRegistry.getAdapter(type) != null);
 	}
 
 
@@ -119,7 +121,7 @@ public ResponseBodyEmitter handleValue(Object returnValue, MethodParameter retur
 			ModelAndViewContainer mav, NativeWebRequest request) throws Exception {
 
 		Assert.notNull(returnValue, "Expected return value");
-		ReactiveAdapter adapter = this.reactiveRegistry.getAdapter(returnValue.getClass());
+		ReactiveAdapter adapter = this.adapterRegistry.getAdapter(returnValue.getClass());
 		Assert.state(adapter != null, () -> "Unexpected return value: " + returnValue);
 
 		ResolvableType elementType = ResolvableType.forMethodParameter(returnType).getGeneric();