Use List<T> instead of Supplier<Stream<T>>

This commit changes all methods that return `Supplier<Stream<T>` to
return `List<T>` instead. This includes the HandlerStrategies, but also
BodyInserter.Context, BodyExtractor.Context, and ServerResponse.Context.

The reason for this change is that most of the strategies have some sort
of order, where more specific message readers - for instance - come
before generic ones. Such an ordering can only be enforced through a
List.

Issue: SPR-15578

spring-webflux/src/main/java/org/springframework/web/reactive/function/BodyExtractor.java

@@ -16,10 +16,9 @@
 
 package org.springframework.web.reactive.function;
 
+import java.util.List;
 import java.util.Map;
 import java.util.Optional;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import org.springframework.http.ReactiveHttpInputMessage;
 import org.springframework.http.codec.HttpMessageReader;
@@ -52,11 +51,10 @@ public interface BodyExtractor<T, M extends ReactiveHttpInputMessage> {
 	interface Context {
 
 		/**
-		 * Supply a {@linkplain Stream stream} of {@link HttpMessageReader}s
+		 * Return the {@link HttpMessageReader}s to be used for body extraction.
-		 * to be used for body extraction.
 		 * @return the stream of message readers
 		 */
-		Supplier<Stream<HttpMessageReader<?>>> messageReaders();
+		List<HttpMessageReader<?>> messageReaders();
 
 		/**
 		 * Optionally return the {@link ServerHttpResponse}, if present.

spring-webflux/src/main/java/org/springframework/web/reactive/function/BodyExtractors.java

@@ -19,9 +19,7 @@ package org.springframework.web.reactive.function;
 import java.util.List;
 import java.util.Optional;
 import java.util.function.Function;
-import java.util.function.Supplier;
 import java.util.stream.Collectors;
-import java.util.stream.Stream;
 
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
@@ -197,14 +195,14 @@ public abstract class BodyExtractors {
 			Function<HttpMessageReader<T>, S> readerFunction, Function<Throwable, S> unsupportedError) {
 
 		MediaType contentType = contentType(inputMessage);
-		Supplier<Stream<HttpMessageReader<?>>> messageReaders = context.messageReaders();
+		List<HttpMessageReader<?>> messageReaders = context.messageReaders();
-		return messageReaders.get()
+		return messageReaders.stream()
 				.filter(r -> r.canRead(elementType, contentType))
 				.findFirst()
 				.map(BodyExtractors::<T>cast)
 				.map(readerFunction)
 				.orElseGet(() -> {
-					List<MediaType> supportedMediaTypes = messageReaders.get()
+					List<MediaType> supportedMediaTypes = messageReaders.stream()
 							.flatMap(reader -> reader.getReadableMediaTypes().stream())
 							.collect(Collectors.toList());
 					UnsupportedMediaTypeException error =
@@ -215,7 +213,7 @@ public abstract class BodyExtractors {
 
 	private static <T> HttpMessageReader<T> messageReader(ResolvableType elementType,
 			MediaType mediaType, BodyExtractor.Context context) {
-		return context.messageReaders().get()
+		return context.messageReaders().stream()
 				.filter(messageReader -> messageReader.canRead(elementType, mediaType))
 				.findFirst()
 				.map(BodyExtractors::<T>cast)

spring-webflux/src/main/java/org/springframework/web/reactive/function/BodyInserter.java

@@ -16,10 +16,9 @@
 
 package org.springframework.web.reactive.function;
 
+import java.util.List;
 import java.util.Map;
 import java.util.Optional;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import reactor.core.publisher.Mono;
 
@@ -54,11 +53,10 @@ public interface BodyInserter<T, M extends ReactiveHttpOutputMessage> {
 	interface Context {
 
 		/**
-		 * Supply a {@linkplain Stream stream} of {@link HttpMessageWriter}s
+		 * Return the {@link HttpMessageWriter}s to be used for response body conversion.
-		 * to be used for response body conversion.
 		 * @return the stream of message writers
 		 */
-		Supplier<Stream<HttpMessageWriter<?>>> messageWriters();
+		List<HttpMessageWriter<?>> messageWriters();
 
 		/**
 		 * Optionally return the {@link ServerHttpRequest}, if present.

spring-webflux/src/main/java/org/springframework/web/reactive/function/BodyInserters.java

@@ -18,9 +18,7 @@ package org.springframework.web.reactive.function;
 
 import java.util.List;
 import java.util.Optional;
-import java.util.function.Supplier;
 import java.util.stream.Collectors;
-import java.util.stream.Stream;
 
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Mono;
@@ -141,7 +139,7 @@ public abstract class BodyInserters {
 	}
 
 	private static HttpMessageWriter<Resource> resourceHttpMessageWriter(BodyInserter.Context context) {
-		return context.messageWriters().get()
+		return context.messageWriters().stream()
 				.filter(messageWriter -> messageWriter.canWrite(RESOURCE_TYPE, null))
 				.findFirst()
 				.map(BodyInserters::<Resource>cast)
@@ -288,8 +286,8 @@ public abstract class BodyInserters {
 
 		return (outputMessage, context) -> {
 			MediaType contentType = outputMessage.getHeaders().getContentType();
-			Supplier<Stream<HttpMessageWriter<?>>> messageWriters = context.messageWriters();
+			List<HttpMessageWriter<?>> messageWriters = context.messageWriters();
-			return messageWriters.get()
+			return messageWriters.stream()
 					.filter(messageWriter -> messageWriter.canWrite(bodyType, contentType))
 					.findFirst()
 					.map(BodyInserters::cast)
@@ -305,7 +303,7 @@ public abstract class BodyInserters {
 						}
 					})
 					.orElseGet(() -> {
-						List<MediaType> supportedMediaTypes = messageWriters.get()
+						List<MediaType> supportedMediaTypes = messageWriters.stream()
 								.flatMap(reader -> reader.getWritableMediaTypes().stream())
 								.collect(Collectors.toList());
 						UnsupportedMediaTypeException error =
@@ -318,7 +316,7 @@ public abstract class BodyInserters {
 	private static <T> HttpMessageWriter<T> findMessageWriter(
 			BodyInserter.Context context, ResolvableType type, MediaType mediaType) {
 
-		return context.messageWriters().get()
+		return context.messageWriters().stream()
 				.filter(messageWriter -> messageWriter.canWrite(type, mediaType))
 				.findFirst()
 				.map(BodyInserters::<T>cast)

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultClientRequestBuilder.java

@@ -18,10 +18,9 @@ package org.springframework.web.reactive.function.client;
 
 import java.net.URI;
 import java.util.Collections;
+import java.util.List;
 import java.util.Map;
 import java.util.Optional;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Mono;
@@ -187,7 +186,7 @@ class DefaultClientRequestBuilder implements ClientRequest.Builder {
 
 			return this.inserter.insert(request, new BodyInserter.Context() {
 				@Override
-				public Supplier<Stream<HttpMessageWriter<?>>> messageWriters() {
+				public List<HttpMessageWriter<?>> messageWriters() {
 					return strategies.messageWriters();
 				}
 

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultClientResponse.java

@@ -21,8 +21,6 @@ import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.OptionalLong;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
@@ -79,7 +77,7 @@ class DefaultClientResponse implements ClientResponse {
 	public <T> T body(BodyExtractor<T, ? super ClientHttpResponse> extractor) {
 		return extractor.extract(this.response, new BodyExtractor.Context() {
 			@Override
-			public Supplier<Stream<HttpMessageReader<?>>> messageReaders() {
+			public List<HttpMessageReader<?>> messageReaders() {
 				return strategies.messageReaders();
 			}
 

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultExchangeStrategiesBuilder.java

@@ -20,8 +20,6 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.function.Consumer;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import org.springframework.http.codec.ClientCodecConfigurer;
 import org.springframework.http.codec.HttpMessageReader;
@@ -88,13 +86,13 @@ class DefaultExchangeStrategiesBuilder implements ExchangeStrategies.Builder {
 		}
 
 		@Override
-		public Supplier<Stream<HttpMessageReader<?>>> messageReaders() {
+		public List<HttpMessageReader<?>> messageReaders() {
-			return this.messageReaders::stream;
+			return this.messageReaders;
 		}
 
 		@Override
-		public Supplier<Stream<HttpMessageWriter<?>>> messageWriters() {
+		public List<HttpMessageWriter<?>> messageWriters() {
-			return this.messageWriters::stream;
+			return this.messageWriters;
 		}
 	}
 

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/ExchangeStrategies.java

@@ -16,9 +16,8 @@
 
 package org.springframework.web.reactive.function.client;
 
+import java.util.List;
 import java.util.function.Consumer;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import org.springframework.http.codec.ClientCodecConfigurer;
 import org.springframework.http.codec.HttpMessageReader;
@@ -28,8 +27,7 @@ import org.springframework.http.codec.HttpMessageWriter;
  * Defines the strategies for invoking {@link ExchangeFunction}s. An instance of
  * this class is immutable; instances are typically created through the mutable {@link Builder}:
  * either through {@link #builder()} to set up default strategies, or {@link #empty()} to start
- * from scratch. Alternatively, {@code ExchangeStrategies} instances can be created through
+ * from scratch.
- * {@link #of(Supplier, Supplier)}.
  *
  * @author Brian Clozel
  * @author Arjen Poutsma
@@ -40,18 +38,16 @@ public interface ExchangeStrategies {
 	// Instance methods
 
 	/**
-	 * Supply a {@linkplain Stream stream} of {@link HttpMessageReader}s to be used for request
+	 * Return the {@link HttpMessageReader}s to be used for request body conversion.
-	 * body conversion.
 	 * @return the stream of message readers
 	 */
-	Supplier<Stream<HttpMessageReader<?>>> messageReaders();
+	List<HttpMessageReader<?>> messageReaders();
 
 	/**
-	 * Supply a {@linkplain Stream stream} of {@link HttpMessageWriter}s to be used for response
+	 * Return the {@link HttpMessageWriter}s to be used for response body conversion.
-	 * body conversion.
 	 * @return the stream of message writers
 	 */
-	Supplier<Stream<HttpMessageWriter<?>>> messageWriters();
+	List<HttpMessageWriter<?>> messageWriters();
 
 
 	// Static methods

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultEntityResponseBuilder.java

@@ -23,11 +23,10 @@ import java.time.format.DateTimeFormatter;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.LinkedHashSet;
+import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import reactor.core.publisher.Mono;
 
@@ -208,7 +207,7 @@ class DefaultEntityResponseBuilder<T> implements EntityResponse.Builder<T> {
 			writeStatusAndHeaders(response);
 			return inserter().insert(response, new BodyInserter.Context() {
 				@Override
-				public Supplier<Stream<HttpMessageWriter<?>>> messageWriters() {
+				public List<HttpMessageWriter<?>> messageWriters() {
 					return context.messageWriters();
 				}
 

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultHandlerStrategiesBuilder.java

@@ -20,8 +20,6 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.function.Consumer;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import org.springframework.http.codec.CodecConfigurer;
 import org.springframework.http.codec.HttpMessageReader;
@@ -135,28 +133,28 @@ class DefaultHandlerStrategiesBuilder implements HandlerStrategies.Builder {
 		}
 
 		@Override
-		public Supplier<Stream<HttpMessageReader<?>>> messageReaders() {
+		public List<HttpMessageReader<?>> messageReaders() {
-			return this.messageReaders::stream;
+			return this.messageReaders;
 		}
 
 		@Override
-		public Supplier<Stream<HttpMessageWriter<?>>> messageWriters() {
+		public List<HttpMessageWriter<?>> messageWriters() {
-			return this.messageWriters::stream;
+			return this.messageWriters;
 		}
 
 		@Override
-		public Supplier<Stream<ViewResolver>> viewResolvers() {
+		public List<ViewResolver> viewResolvers() {
-			return this.viewResolvers::stream;
+			return this.viewResolvers;
 		}
 
 		@Override
-		public Supplier<Stream<WebFilter>> webFilters() {
+		public List<WebFilter> webFilters() {
-			return this.webFilters::stream;
+			return this.webFilters;
 		}
 
 		@Override
-		public Supplier<Stream<WebExceptionHandler>> exceptionHandlers() {
+		public List<WebExceptionHandler> exceptionHandlers() {
-			return this.exceptionHandlers::stream;
+			return this.exceptionHandlers;
 		}
 	}
 

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultRenderingResponseBuilder.java

@@ -164,7 +164,7 @@ class DefaultRenderingResponseBuilder implements RenderingResponse.Builder {
 			writeStatusAndHeaders(response);
 			MediaType contentType = exchange.getResponse().getHeaders().getContentType();
 			Locale locale = resolveLocale(exchange);
-			Stream<ViewResolver> viewResolverStream = context.viewResolvers().get();
+			Stream<ViewResolver> viewResolverStream = context.viewResolvers().stream();
 
 			return Flux.fromStream(viewResolverStream)
 					.concatMap(viewResolver -> viewResolver.resolveViewName(name(), locale))

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultServerRequest.java

@@ -20,6 +20,7 @@ import java.net.InetSocketAddress;
 import java.net.URI;
 import java.nio.charset.Charset;
 import java.security.Principal;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
@@ -27,8 +28,6 @@ import java.util.Map;
 import java.util.Optional;
 import java.util.OptionalLong;
 import java.util.function.Function;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
@@ -66,15 +65,20 @@ class DefaultServerRequest implements ServerRequest {
 
 	private final Headers headers;
 
-	private final Supplier<Stream<HttpMessageReader<?>>> messageReaders;
+	private final List<HttpMessageReader<?>> messageReaders;
 
 
-	DefaultServerRequest(ServerWebExchange exchange, Supplier<Stream<HttpMessageReader<?>>> messageReaders) {
+	DefaultServerRequest(ServerWebExchange exchange, List<HttpMessageReader<?>> messageReaders) {
 		this.exchange = exchange;
-		this.messageReaders = messageReaders;
+		this.messageReaders = unmodifiableCopy(messageReaders);
 		this.headers = new DefaultHeaders();
 	}
 
+	private static <T> List<T> unmodifiableCopy(List<? extends T> list) {
+		return Collections.unmodifiableList(new ArrayList<>(list));
+	}
+
+
 
 	@Override
 	public HttpMethod method() {
@@ -102,8 +106,8 @@ class DefaultServerRequest implements ServerRequest {
 		return extractor.extract(request(),
 				new BodyExtractor.Context() {
 					@Override
-					public Supplier<Stream<HttpMessageReader<?>>> messageReaders() {
+					public List<HttpMessageReader<?>> messageReaders() {
-						return DefaultServerRequest.this.messageReaders;
+						return messageReaders;
 					}
 					@Override
 					public Optional<ServerHttpResponse> serverResponse() {

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultServerResponseBuilder.java

@@ -23,12 +23,11 @@ import java.time.format.DateTimeFormatter;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.LinkedHashSet;
+import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
 import java.util.function.BiFunction;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Mono;
@@ -314,7 +313,7 @@ class DefaultServerResponseBuilder implements ServerResponse.BodyBuilder {
 			writeStatusAndHeaders(response);
 			return this.inserter.insert(response, new BodyInserter.Context() {
 				@Override
-				public Supplier<Stream<HttpMessageWriter<?>>> messageWriters() {
+				public List<HttpMessageWriter<?>> messageWriters() {
 					return context.messageWriters();
 				}
 

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/HandlerStrategies.java

@@ -16,9 +16,8 @@
 
 package org.springframework.web.reactive.function.server;
 
+import java.util.List;
 import java.util.function.Consumer;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import org.springframework.http.codec.HttpMessageReader;
 import org.springframework.http.codec.HttpMessageWriter;
@@ -43,39 +42,34 @@ public interface HandlerStrategies {
 	// Instance methods
 
 	/**
-	 * Supply a {@linkplain Stream stream} of {@link HttpMessageReader}s to be used for request
+	 * Return the {@link HttpMessageReader}s to be used for request body conversion.
-	 * body conversion.
+	 * @return the message readers
-	 * @return the stream of message readers
 	 */
-	Supplier<Stream<HttpMessageReader<?>>> messageReaders();
+	List<HttpMessageReader<?>> messageReaders();
 
 	/**
-	 * Supply a {@linkplain Stream stream} of {@link HttpMessageWriter}s to be used for response
+	 * Return the {@link HttpMessageWriter}s to be used for response body conversion.
-	 * body conversion.
+	 * @return the message writers
-	 * @return the stream of message writers
 	 */
-	Supplier<Stream<HttpMessageWriter<?>>> messageWriters();
+	List<HttpMessageWriter<?>> messageWriters();
 
 	/**
-	 * Supply a {@linkplain Stream stream} of {@link ViewResolver}s to be used for view name
+	 * Return the {@link ViewResolver}s to be used for view name resolution.
-	 * resolution.
+	 * @return the view resolvers
-	 * @return the stream of view resolvers
 	 */
-	Supplier<Stream<ViewResolver>> viewResolvers();
+	List<ViewResolver> viewResolvers();
 
 	/**
-	 * Supply a {@linkplain Stream stream} of {@link WebFilter}s to be used for filtering the
+	 * Return the {@link WebFilter}s to be used for filtering the request and response.
-	 * request and response.
+	 * @return the web filters
-	 * @return the stream of web filters
 	 */
-	Supplier<Stream<WebFilter>> webFilters();
+	List<WebFilter> webFilters();
 
 	/**
-	 * Supply a {@linkplain Stream stream} of {@link WebExceptionHandler}s to be used for handling
+	 * Return the {@link WebExceptionHandler}s to be used for handling exceptions.
-	 * exceptions.
+	 * @return the exception handlers
-	 * @return the stream of exception handlers
 	 */
-	Supplier<Stream<WebExceptionHandler>> exceptionHandlers();
+	List<WebExceptionHandler> exceptionHandlers();
 
 
 	// Static methods

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/RouterFunctions.java

@@ -16,10 +16,10 @@
 
 package org.springframework.web.reactive.function.server;
 
+import java.util.List;
 import java.util.Map;
 import java.util.function.Function;
 import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -45,9 +45,6 @@ import org.springframework.web.server.adapter.WebHttpHandlerBuilder;
  * <p>Additionally, this class can {@linkplain #toHttpHandler(RouterFunction) transform} a
  * {@code RouterFunction} into an {@code HttpHandler}, which can be run in Servlet 3.1+,
  * Reactor, or Undertow.
- * And it can {@linkplain #toHandlerMapping(RouterFunction, HandlerStrategies) transform} a
- * {@code RouterFunction} into an {@code HandlerMapping}, which can be run in a
- * {@code DispatcherHandler}.
  *
  * @author Arjen Poutsma
  * @since 5.0
@@ -199,10 +196,10 @@ public abstract class RouterFunctions {
 		Assert.notNull(strategies, "HandlerStrategies must not be null");
 
 		WebHandler webHandler = toWebHandler(routerFunction, strategies);
-		WebHttpHandlerBuilder handlerBuilder = WebHttpHandlerBuilder.webHandler(webHandler);
+		return WebHttpHandlerBuilder.webHandler(webHandler)
-		strategies.webFilters().get().forEach(handlerBuilder::filter);
+				.filters(strategies.webFilters())
-		strategies.exceptionHandlers().get().forEach(handlerBuilder::exceptionHandler);
+				.exceptionHandlers(strategies.exceptionHandlers())
-		return handlerBuilder.build();
+				.build();
 	}
 
 	/**
@@ -222,7 +219,8 @@ public abstract class RouterFunctions {
 			return routerFunction.route(request)
 					.defaultIfEmpty(notFound())
 					.flatMap(handlerFunction -> wrapException(() -> handlerFunction.handle(request)))
-					.flatMap(response -> wrapException(() -> response.writeTo(exchange, toContext(strategies))));
+					.flatMap(response -> wrapException(() -> response.writeTo(exchange,
+							new HandlerStrategiesResponseContext(strategies))));
 		};
 	}
 
@@ -235,20 +233,6 @@ public abstract class RouterFunctions {
 		}
 	}
 
-	private static ServerResponse.Context toContext(HandlerStrategies strategies) {
-		return new ServerResponse.Context() {
-			@Override
-			public Supplier<Stream<HttpMessageWriter<?>>> messageWriters() {
-				return strategies.messageWriters();
-			}
-
-			@Override
-			public Supplier<Stream<ViewResolver>> viewResolvers() {
-				return strategies.viewResolvers();
-			}
-		};
-	}
-
 	private static void addAttributes(ServerWebExchange exchange, ServerRequest request) {
 		Map<String, Object> attributes = exchange.getAttributes();
 		attributes.put(REQUEST_ATTRIBUTE, request);
@@ -332,4 +316,23 @@ public abstract class RouterFunctions {
 		}
 
 	}
+
+	private static class HandlerStrategiesResponseContext implements ServerResponse.Context {
+
+		private final HandlerStrategies strategies;
+
+		public HandlerStrategiesResponseContext(HandlerStrategies strategies) {
+			this.strategies = strategies;
+		}
+
+		@Override
+		public List<HttpMessageWriter<?>> messageWriters() {
+			return this.strategies.messageWriters();
+		}
+
+		@Override
+		public List<ViewResolver> viewResolvers() {
+			return this.strategies.viewResolvers();
+		}
+	}
 }

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/ServerRequest.java

@@ -187,7 +187,7 @@ public interface ServerRequest {
 	static ServerRequest create(ServerWebExchange exchange,
 			List<HttpMessageReader<?>> messageReaders) {
 
-		return new DefaultServerRequest(exchange, messageReaders::stream);
+		return new DefaultServerRequest(exchange, messageReaders);
 	}
 
 	/**

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/ServerResponse.java

@@ -19,11 +19,10 @@ package org.springframework.web.reactive.function.server;
 import java.net.URI;
 import java.time.ZonedDateTime;
 import java.util.Collection;
+import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.function.BiFunction;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Mono;
@@ -395,18 +394,16 @@ public interface ServerResponse {
 	interface Context {
 
 		/**
-		 * Supply a {@linkplain Stream stream} of {@link HttpMessageWriter}s
+		 * Return the {@link HttpMessageWriter}s to be used for response body conversion.
-		 * to be used for response body conversion.
 		 * @return the stream of message writers
 		 */
-		Supplier<Stream<HttpMessageWriter<?>>> messageWriters();
+		List<HttpMessageWriter<?>> messageWriters();
 
 		/**
-		 * Supply a {@linkplain Stream stream} of {@link ViewResolver}s to be used for view name
+		 * Return the  {@link ViewResolver}s to be used for view name resolution.
-		 * resolution.
 		 * @return the stream of view resolvers
 		 */
-		Supplier<Stream<ViewResolver>> viewResolvers();
+		List<ViewResolver> viewResolvers();
 	}
 
 

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/support/ServerResponseResultHandler.java

@@ -18,8 +18,6 @@ package org.springframework.web.reactive.function.server.support;
 
 import java.util.Collections;
 import java.util.List;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import reactor.core.publisher.Mono;
 
@@ -99,13 +97,13 @@ public class ServerResponseResultHandler implements HandlerResultHandler, Initia
 		Assert.state(response != null, "No ServerResponse");
 		return response.writeTo(exchange, new ServerResponse.Context() {
 			@Override
-			public Supplier<Stream<HttpMessageWriter<?>>> messageWriters() {
+			public List<HttpMessageWriter<?>> messageWriters() {
-				return messageCodecConfigurer.getWriters()::stream;
+				return messageCodecConfigurer.getWriters();
 			}
 
 			@Override
-			public Supplier<Stream<ViewResolver>> viewResolvers() {
+			public List<ViewResolver> viewResolvers() {
-				return viewResolvers::stream;
+				return viewResolvers;
 			}
 		});
 	}

spring-webflux/src/test/java/org/springframework/web/reactive/function/BodyExtractorsTests.java

@@ -24,8 +24,6 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import com.fasterxml.jackson.annotation.JsonView;
 import org.junit.Before;
@@ -86,8 +84,8 @@ public class BodyExtractorsTests {
 
 		this.context = new BodyExtractor.Context() {
 			@Override
-			public Supplier<Stream<HttpMessageReader<?>>> messageReaders() {
+			public List<HttpMessageReader<?>> messageReaders() {
-				return messageReaders::stream;
+				return messageReaders;
 			}
 
 			@Override
@@ -209,8 +207,8 @@ public class BodyExtractorsTests {
 
 		BodyExtractor.Context emptyContext = new BodyExtractor.Context() {
 			@Override
-			public Supplier<Stream<HttpMessageReader<?>>> messageReaders() {
+			public List<HttpMessageReader<?>> messageReaders() {
-				return Stream::empty;
+				return Collections.emptyList();
 			}
 
 			@Override

spring-webflux/src/test/java/org/springframework/web/reactive/function/BodyInsertersTests.java

@@ -26,8 +26,6 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import com.fasterxml.jackson.annotation.JsonView;
 import org.junit.Before;
@@ -93,8 +91,8 @@ public class BodyInsertersTests {
 
 		this.context = new BodyInserter.Context() {
 			@Override
-			public Supplier<Stream<HttpMessageWriter<?>>> messageWriters() {
+			public List<HttpMessageWriter<?>> messageWriters() {
-				return messageWriters::stream;
+				return messageWriters;
 			}
 
 			@Override
@@ -207,8 +205,8 @@ public class BodyInsertersTests {
 		MockServerHttpResponse response = new MockServerHttpResponse();
 		Mono<Void> result = inserter.insert(response, new BodyInserter.Context() {
 			@Override
-			public Supplier<Stream<HttpMessageWriter<?>>> messageWriters() {
+			public List<HttpMessageWriter<?>> messageWriters() {
-				return Collections.<HttpMessageWriter<?>>singleton(new ResourceHttpMessageWriter())::stream;
+				return Collections.singletonList(new ResourceHttpMessageWriter());
 			}
 
 			@Override

spring-webflux/src/test/java/org/springframework/web/reactive/function/client/DefaultClientRequestBuilderTests.java

@@ -34,10 +34,12 @@ import org.springframework.http.codec.HttpMessageWriter;
 import org.springframework.mock.http.client.reactive.test.MockClientHttpRequest;
 import org.springframework.web.reactive.function.BodyInserter;
 
-import static java.nio.charset.StandardCharsets.*;
+import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.junit.Assert.*;
 import static org.mockito.Mockito.*;
-import static org.springframework.http.HttpMethod.*;
+import static org.springframework.http.HttpMethod.DELETE;
+import static org.springframework.http.HttpMethod.GET;
+import static org.springframework.http.HttpMethod.POST;
 
 /**
  * @author Arjen Poutsma
@@ -107,7 +109,7 @@ public class DefaultClientRequestBuilderTests {
 		messageWriters.add(new EncoderHttpMessageWriter<>(CharSequenceEncoder.allMimeTypes()));
 
 		ExchangeStrategies strategies = mock(ExchangeStrategies.class);
-		when(strategies.messageWriters()).thenReturn(messageWriters::stream);
+		when(strategies.messageWriters()).thenReturn(messageWriters);
 
 		MockClientHttpRequest request = new MockClientHttpRequest(GET, "/");
 		result.writeTo(request, strategies).block();

spring-webflux/src/test/java/org/springframework/web/reactive/function/client/DefaultClientResponseTests.java

@@ -23,7 +23,6 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 import java.util.OptionalLong;
-import java.util.Set;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -121,9 +120,9 @@ public class DefaultClientResponseTests {
 		when(mockResponse.getHeaders()).thenReturn(httpHeaders);
 		when(mockResponse.getBody()).thenReturn(body);
 
-		Set<HttpMessageReader<?>> messageReaders = Collections
+		List<HttpMessageReader<?>> messageReaders = Collections
-				.singleton(new DecoderHttpMessageReader<>(StringDecoder.allMimeTypes(true)));
+				.singletonList(new DecoderHttpMessageReader<>(StringDecoder.allMimeTypes(true)));
-		when(mockExchangeStrategies.messageReaders()).thenReturn(messageReaders::stream);
+		when(mockExchangeStrategies.messageReaders()).thenReturn(messageReaders);
 
 		Mono<String> resultMono = defaultClientResponse.body(toMono(String.class));
 		assertEquals("foo", resultMono.block());
@@ -142,9 +141,9 @@ public class DefaultClientResponseTests {
 		when(mockResponse.getStatusCode()).thenReturn(HttpStatus.OK);
 		when(mockResponse.getBody()).thenReturn(body);
 
-		Set<HttpMessageReader<?>> messageReaders = Collections
+		List<HttpMessageReader<?>> messageReaders = Collections
-				.singleton(new DecoderHttpMessageReader<>(StringDecoder.allMimeTypes(true)));
+				.singletonList(new DecoderHttpMessageReader<>(StringDecoder.allMimeTypes(true)));
-		when(mockExchangeStrategies.messageReaders()).thenReturn(messageReaders::stream);
+		when(mockExchangeStrategies.messageReaders()).thenReturn(messageReaders);
 
 		Mono<String> resultMono = defaultClientResponse.bodyToMono(String.class);
 		assertEquals("foo", resultMono.block());
@@ -163,9 +162,9 @@ public class DefaultClientResponseTests {
 		when(mockResponse.getStatusCode()).thenReturn(HttpStatus.OK);
 		when(mockResponse.getBody()).thenReturn(body);
 
-		Set<HttpMessageReader<?>> messageReaders = Collections
+		List<HttpMessageReader<?>> messageReaders = Collections
-				.singleton(new DecoderHttpMessageReader<>(StringDecoder.allMimeTypes(true)));
+				.singletonList(new DecoderHttpMessageReader<>(StringDecoder.allMimeTypes(true)));
-		when(mockExchangeStrategies.messageReaders()).thenReturn(messageReaders::stream);
+		when(mockExchangeStrategies.messageReaders()).thenReturn(messageReaders);
 
 		Flux<String> resultFlux = defaultClientResponse.bodyToFlux(String.class);
 		Mono<List<String>> result = resultFlux.collectList();

spring-webflux/src/test/java/org/springframework/web/reactive/function/client/ExchangeStrategiesTests.java

@@ -16,8 +16,6 @@
 
 package org.springframework.web.reactive.function.client;
 
-import java.util.Optional;
-
 import org.junit.Test;
 
 import static org.junit.Assert.*;
@@ -30,15 +28,15 @@ public class ExchangeStrategiesTests {
 	@Test
 	public void empty() {
 		ExchangeStrategies strategies = ExchangeStrategies.empty().build();
-		assertEquals(Optional.empty(), strategies.messageReaders().get().findFirst());
+		assertTrue(strategies.messageReaders().isEmpty());
-		assertEquals(Optional.empty(), strategies.messageWriters().get().findFirst());
+		assertTrue(strategies.messageWriters().isEmpty());
 	}
 
 	@Test
 	public void withDefaults() {
 		ExchangeStrategies strategies = ExchangeStrategies.withDefaults();
-		assertNotEquals(Optional.empty(), strategies.messageReaders().get().findFirst());
+		assertFalse(strategies.messageReaders().isEmpty());
-		assertNotEquals(Optional.empty(), strategies.messageWriters().get().findFirst());
+		assertFalse(strategies.messageWriters().isEmpty());
 	}
 
 }

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/DefaultEntityResponseBuilderTests.java

@@ -23,8 +23,6 @@ import java.util.EnumSet;
 import java.util.List;
 import java.util.Set;
 import java.util.function.BiFunction;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import org.junit.Test;
 import org.reactivestreams.Publisher;
@@ -196,13 +194,13 @@ public class DefaultEntityResponseBuilderTests {
 
 		ServerResponse.Context context = new ServerResponse.Context() {
 			@Override
-			public Supplier<Stream<HttpMessageWriter<?>>> messageWriters() {
+			public List<HttpMessageWriter<?>> messageWriters() {
-				return Collections.<HttpMessageWriter<?>>singletonList(new EncoderHttpMessageWriter<>(CharSequenceEncoder.allMimeTypes()))::stream;
+				return Collections.<HttpMessageWriter<?>>singletonList(new EncoderHttpMessageWriter<>(CharSequenceEncoder.allMimeTypes()));
 			}
 
 			@Override
-			public Supplier<Stream<ViewResolver>> viewResolvers() {
+			public List<ViewResolver> viewResolvers() {
-				return Collections.<ViewResolver>emptyList()::stream;
+				return Collections.<ViewResolver>emptyList();
 			}
 		};
 		HandlerStrategies strategies = HandlerStrategies.empty()

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/DefaultRenderingResponseTests.java

@@ -33,8 +33,7 @@ import org.springframework.mock.http.server.reactive.test.MockServerWebExchange;
 import org.springframework.web.reactive.result.view.View;
 import org.springframework.web.reactive.result.view.ViewResolver;
 
-import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.*;
-import static org.mockito.Mockito.when;
 
 /**
  * @author Arjen Poutsma
@@ -119,7 +118,7 @@ public class DefaultRenderingResponseTests {
 		viewResolvers.add(viewResolver);
 
 		HandlerStrategies mockConfig = mock(HandlerStrategies.class);
-		when(mockConfig.viewResolvers()).thenReturn(viewResolvers::stream);
+		when(mockConfig.viewResolvers()).thenReturn(viewResolvers);
 
 		StepVerifier.create(result)
 				.expectNextMatches(response -> "view".equals(response.name()) &&

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/DefaultServerRequestTests.java

@@ -26,8 +26,6 @@ import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.OptionalLong;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -66,7 +64,7 @@ public class DefaultServerRequestTests {
 
 	private ServerWebExchange mockExchange;
 
-	Supplier<Stream<HttpMessageReader<?>>> messageReaders;
+	List<HttpMessageReader<?>> messageReaders;
 
 	private DefaultServerRequest defaultRequest;
 
@@ -80,7 +78,7 @@ public class DefaultServerRequestTests {
 		when(mockExchange.getRequest()).thenReturn(mockRequest);
 		when(mockExchange.getResponse()).thenReturn(mockResponse);
 
-		this.messageReaders = Collections.<HttpMessageReader<?>>singleton(new DecoderHttpMessageReader<>(StringDecoder.allMimeTypes(true)))::stream;
+		this.messageReaders = Collections.<HttpMessageReader<?>>singletonList(new DecoderHttpMessageReader<>(StringDecoder.allMimeTypes(true)));
 
 		defaultRequest = new DefaultServerRequest(mockExchange, messageReaders);
 	}
@@ -238,7 +236,7 @@ public class DefaultServerRequestTests {
 		when(mockRequest.getHeaders()).thenReturn(httpHeaders);
 		when(mockRequest.getBody()).thenReturn(body);
 
-		this.messageReaders = Collections.<HttpMessageReader<?>>emptySet()::stream;
+		this.messageReaders = Collections.emptyList();
 		this.defaultRequest = new DefaultServerRequest(mockExchange, messageReaders);
 
 		Flux<String> resultFlux = defaultRequest.bodyToFlux(String.class);

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/HandlerStrategiesTests.java

@@ -16,8 +16,6 @@
 
 package org.springframework.web.reactive.function.server;
 
-import java.util.Optional;
-
 import org.junit.Test;
 
 import static org.junit.Assert.*;
@@ -30,17 +28,17 @@ public class HandlerStrategiesTests {
 	@Test
 	public void empty() {
 		HandlerStrategies strategies = HandlerStrategies.empty().build();
-		assertEquals(Optional.empty(), strategies.messageReaders().get().findFirst());
+		assertTrue(strategies.messageReaders().isEmpty());
-		assertEquals(Optional.empty(), strategies.messageWriters().get().findFirst());
+		assertTrue(strategies.messageWriters().isEmpty());
-		assertEquals(Optional.empty(), strategies.viewResolvers().get().findFirst());
+		assertTrue(strategies.viewResolvers().isEmpty());
 	}
 
 	@Test
 	public void withDefaults() {
 		HandlerStrategies strategies = HandlerStrategies.withDefaults();
-		assertNotEquals(Optional.empty(), strategies.messageReaders().get().findFirst());
+		assertFalse(strategies.messageReaders().isEmpty());
-		assertNotEquals(Optional.empty(), strategies.messageWriters().get().findFirst());
+		assertFalse(strategies.messageWriters().isEmpty());
-		assertEquals(Optional.empty(), strategies.viewResolvers().get().findFirst());
+		assertTrue(strategies.viewResolvers().isEmpty());
 	}
 
 }

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/ResourceHandlerFunctionTests.java

@@ -19,8 +19,7 @@ package org.springframework.web.reactive.function.server;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.util.EnumSet;
-import java.util.function.Supplier;
+import java.util.List;
-import java.util.stream.Stream;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -56,12 +55,12 @@ public class ResourceHandlerFunctionTests {
 		HandlerStrategies strategies = HandlerStrategies.withDefaults();
 		context = new ServerResponse.Context() {
 			@Override
-			public Supplier<Stream<HttpMessageWriter<?>>> messageWriters() {
+			public List<HttpMessageWriter<?>> messageWriters() {
 				return strategies.messageWriters();
 			}
 
 			@Override
-			public Supplier<Stream<ViewResolver>> viewResolvers() {
+			public List<ViewResolver> viewResolvers() {
 				return strategies.viewResolvers();
 			}
 		};