Avoid java.util.Optional signatures for simple field access

Issue: SPR-15576

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -16,7 +16,6 @@
 
 package org.springframework.web.reactive;
 
-import java.util.Optional;
 import java.util.function.Function;
 
 import reactor.core.publisher.Mono;
@@ -82,10 +81,10 @@ public class HandlerResult {
 	}
 
 	/**
-	 * Return the value returned from the handler wrapped as {@link Optional}.
+	 * Return the value returned from the handler, if any.
 	 */
-	public Optional<Object> getReturnValue() {
-		return Optional.ofNullable(this.returnValue);
+	public Object getReturnValue() {
+		return this.returnValue;
 	}
 
 	/**

spring-webflux/src/main/java/org/springframework/web/reactive/config/DelegatingWebFluxConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -86,12 +86,14 @@ public class DelegatingWebFluxConfiguration extends WebFluxConfigurationSupport
 
 	@Override
 	protected Validator getValidator() {
-		return this.configurers.getValidator().orElse(super.getValidator());
+		Validator validator = this.configurers.getValidator();
+		return (validator != null ? validator : super.getValidator());
 	}
 
 	@Override
 	protected MessageCodesResolver getMessageCodesResolver() {
-		return this.configurers.getMessageCodesResolver().orElse(super.getMessageCodesResolver());
+		MessageCodesResolver messageCodesResolver = this.configurers.getMessageCodesResolver();
+		return (messageCodesResolver != null ? messageCodesResolver : super.getMessageCodesResolver());
 	}
 
 	@Override

spring-webflux/src/main/java/org/springframework/web/reactive/config/WebFluxConfigurer.java

@@ -16,8 +16,6 @@
 
 package org.springframework.web.reactive.config;
 
-import java.util.Optional;
-
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.format.Formatter;
 import org.springframework.format.FormatterRegistry;
@@ -104,17 +102,16 @@ public interface WebFluxConfigurer {
 	 * <p>By default a validator for standard bean validation is created if
 	 * bean validation api is present on the classpath.
 	 */
-	default Optional<Validator> getValidator() {
-		return Optional.empty();
+	default Validator getValidator() {
+		return null;
 	}
 
 	/**
-	 * Provide a custom {@link MessageCodesResolver} to use for data binding
-	 * instead of the one created by default in
-	 * {@link org.springframework.validation.DataBinder}.
+	 * Provide a custom {@link MessageCodesResolver} to use for data binding instead
+	 * of the one created by default in {@link org.springframework.validation.DataBinder}.
 	 */
-	default Optional<MessageCodesResolver> getMessageCodesResolver() {
-		return Optional.empty();
+	default MessageCodesResolver getMessageCodesResolver() {
+		return null;
 	}
 
 	/**

spring-webflux/src/main/java/org/springframework/web/reactive/config/WebFluxConfigurerComposite.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -18,7 +18,6 @@ package org.springframework.web.reactive.config;
 
 import java.util.ArrayList;
 import java.util.List;
-import java.util.Optional;
 import java.util.function.Function;
 import java.util.stream.Collectors;
 
@@ -85,12 +84,12 @@ public class WebFluxConfigurerComposite implements WebFluxConfigurer {
 	}
 
 	@Override
-	public Optional<Validator> getValidator() {
+	public Validator getValidator() {
 		return createSingleBean(WebFluxConfigurer::getValidator, Validator.class);
 	}
 
 	@Override
-	public Optional<MessageCodesResolver> getMessageCodesResolver() {
+	public MessageCodesResolver getMessageCodesResolver() {
 		return createSingleBean(WebFluxConfigurer::getMessageCodesResolver, MessageCodesResolver.class);
 	}
 
@@ -99,14 +98,10 @@ public class WebFluxConfigurerComposite implements WebFluxConfigurer {
 		this.delegates.forEach(delegate -> delegate.configureViewResolvers(registry));
 	}
 
-	private <T> Optional<T> createSingleBean(Function<WebFluxConfigurer, Optional<T>> factory,
-			Class<T> beanType) {
-
-		List<Optional<T>> result = this.delegates.stream()
-				.map(factory).filter(Optional::isPresent).collect(Collectors.toList());
-
+	private <T> T createSingleBean(Function<WebFluxConfigurer, T> factory, Class<T> beanType) {
+		List<T> result = this.delegates.stream().map(factory).filter(t -> t != null).collect(Collectors.toList());
 		if (result.isEmpty()) {
-			return Optional.empty();
+			return null;
 		}
 		else if (result.size() == 1) {
 			return result.get(0);

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

@@ -57,10 +57,11 @@ public class UnsupportedMediaTypeException extends NestedRuntimeException {
 
 
 	/**
-	 * Return the request Content-Type header if it was parsed successfully.
+	 * Return the request Content-Type header if it was parsed successfully,
+	 * or {@code null} otherwise.
 	 */
-	public Optional<MediaType> getContentType() {
-		return Optional.ofNullable(this.contentType);
+	public MediaType getContentType() {
+		return this.contentType;
 	}
 
 	/**

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

@@ -57,10 +57,10 @@ import org.springframework.web.server.WebSession;
 class DefaultServerRequest implements ServerRequest {
 
 	private static final Function<UnsupportedMediaTypeException, UnsupportedMediaTypeStatusException> ERROR_MAPPER =
-			ex -> ex.getContentType()
-					.map(contentType -> new UnsupportedMediaTypeStatusException(contentType,
-							ex.getSupportedMediaTypes()))
-					.orElseGet(() -> new UnsupportedMediaTypeStatusException(ex.getMessage()));
+			ex -> (ex.getContentType() != null ?
+					new UnsupportedMediaTypeStatusException(ex.getContentType(), ex.getSupportedMediaTypes()) :
+					new UnsupportedMediaTypeStatusException(ex.getMessage()));
+
 
 	private final ServerWebExchange exchange;
 
@@ -69,8 +69,7 @@ class DefaultServerRequest implements ServerRequest {
 	private final Supplier<Stream<HttpMessageReader<?>>> messageReaders;
 
 
-	DefaultServerRequest(ServerWebExchange exchange,
-			Supplier<Stream<HttpMessageReader<?>>> messageReaders) {
+	DefaultServerRequest(ServerWebExchange exchange, Supplier<Stream<HttpMessageReader<?>>> messageReaders) {
 		this.exchange = exchange;
 		this.messageReaders = messageReaders;
 		this.headers = new DefaultHeaders();
@@ -106,12 +105,10 @@ class DefaultServerRequest implements ServerRequest {
 					public Supplier<Stream<HttpMessageReader<?>>> messageReaders() {
 						return DefaultServerRequest.this.messageReaders;
 					}
-
 					@Override
 					public Optional<ServerHttpResponse> serverResponse() {
 						return Optional.of(exchange().getResponse());
 					}
-
 					@Override
 					public Map<String, Object> hints() {
 						return hints;

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

@@ -54,14 +54,13 @@ public class ServerResponseResultHandler implements HandlerResultHandler {
 
 	@Override
 	public boolean supports(HandlerResult result) {
-		return result.getReturnValue()
-				.filter(o -> o instanceof ServerResponse)
-				.isPresent();
+		return (result.getReturnValue() instanceof ServerResponse);
 	}
 
 	@Override
 	public Mono<Void> handleResult(ServerWebExchange exchange, HandlerResult result) {
-		ServerResponse response = (ServerResponse) result.getReturnValue().orElseThrow(IllegalStateException::new);
+		ServerResponse response = (ServerResponse) result.getReturnValue();
+		Assert.state(response != null, "No ServerResponse");
 		return response.writeTo(exchange, this.strategies);
 	}
 

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/annotation/InitBinderBindingContext.java

@@ -19,7 +19,6 @@ package org.springframework.web.reactive.result.method.annotation;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
-import java.util.Optional;
 
 import org.springframework.web.bind.annotation.InitBinder;
 import org.springframework.web.bind.support.WebBindingInitializer;
@@ -69,17 +68,15 @@ class InitBinderBindingContext extends BindingContext {
 	private void invokeBinderMethod(WebExchangeDataBinder dataBinder,
 			ServerWebExchange exchange, SyncInvocableHandlerMethod binderMethod) {
 
-		Optional<Object> returnValue = binderMethod
-				.invokeForHandlerResult(exchange, this.binderMethodContext, dataBinder)
+		Object returnValue = binderMethod.invokeForHandlerResult(exchange, this.binderMethodContext, dataBinder)
 				.getReturnValue();
 
-		if (returnValue.isPresent()) {
+		if (returnValue != null) {
 			throw new IllegalStateException(
 					"@InitBinder methods should return void: " + binderMethod);
 		}
 
 		// Should not happen (no Model argument resolution) ...
-
 		if (!this.binderMethodContext.getModel().asMap().isEmpty()) {
 			throw new IllegalStateException(
 					"@InitBinder methods should not add model attributes: " + binderMethod);

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/annotation/ModelInitializer.java

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.reactive.result.method.annotation;
 
 import java.util.ArrayList;
@@ -36,7 +37,6 @@ import org.springframework.web.reactive.HandlerResult;
 import org.springframework.web.reactive.result.method.InvocableHandlerMethod;
 import org.springframework.web.server.ServerWebExchange;
 
-
 /**
  * Package-private class to assist {@link RequestMappingHandlerAdapter} with
  * default model initialization through {@code @ModelAttribute} methods.
@@ -54,24 +54,16 @@ class ModelInitializer {
 	}
 
 
-	private ReactiveAdapterRegistry getAdapterRegistry() {
-		return this.adapterRegistry;
-	}
-
-
 	/**
 	 * Initialize the default model in the given {@code BindingContext} through
 	 * the {@code @ModelAttribute} methods and indicate when complete.
-	 *
 	 * <p>This will wait for {@code @ModelAttribute} methods that return
 	 * {@code Mono<Void>} since those may be adding attributes asynchronously.
 	 * However if methods return async attributes, those will be added to the
 	 * model as-is and without waiting for them to be resolved.
-	 *
 	 * @param bindingContext the BindingContext with the default model
 	 * @param attributeMethods the {@code @ModelAttribute} methods
 	 * @param exchange the current exchange
-	 *
 	 * @return a {@code Mono} for when the model is populated.
 	 */
 	@SuppressWarnings("Convert2MethodRef")
@@ -90,28 +82,20 @@ class ModelInitializer {
 	}
 
 	private Mono<Void> handleResult(HandlerResult handlerResult, BindingContext bindingContext) {
-
-		return handlerResult.getReturnValue()
-				.map(value -> {
-					ResolvableType type = handlerResult.getReturnType();
-					ReactiveAdapter adapter = getAdapterRegistry().getAdapter(type.getRawClass(), value);
-
-					Class<?> attributeType;
-					if (adapter != null) {
-						attributeType = adapter.isNoValue() ? Void.class : type.resolveGeneric(0);
-						if (attributeType.equals(Void.class)) {
-							return Mono.<Void>from(adapter.toPublisher(value));
-						}
-					}
-					else {
-						attributeType = type.resolve();
-					}
-
-					String name = getAttributeName(handlerResult.getReturnTypeSource());
-					bindingContext.getModel().asMap().putIfAbsent(name, value);
-					return Mono.<Void>empty();
-				})
-				.orElse(Mono.empty());
+		Object value = handlerResult.getReturnValue();
+		if (value != null) {
+			ResolvableType type = handlerResult.getReturnType();
+			ReactiveAdapter adapter = this.adapterRegistry.getAdapter(type.getRawClass(), value);
+			if (adapter != null) {
+				Class<?> attributeType = (adapter.isNoValue() ? Void.class : type.resolveGeneric());
+				if (attributeType == Void.class) {
+					return Mono.from(adapter.toPublisher(value));
+				}
+			}
+			String name = getAttributeName(handlerResult.getReturnTypeSource());
+			bindingContext.getModel().asMap().putIfAbsent(name, value);
+		}
+		return Mono.empty();
 	}
 
 	private String getAttributeName(MethodParameter param) {

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/annotation/ResponseBodyResultHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -30,7 +30,6 @@ import org.springframework.web.reactive.HandlerResultHandler;
 import org.springframework.web.reactive.accept.RequestedContentTypeResolver;
 import org.springframework.web.server.ServerWebExchange;
 
-
 /**
  * {@code HandlerResultHandler} that handles return values from methods annotated
  * with {@code @ResponseBody} writing to the body of the request or response with
@@ -47,9 +46,7 @@ import org.springframework.web.server.ServerWebExchange;
  * @author Arjen Poutsma
  * @since 5.0
  */
-public class ResponseBodyResultHandler extends AbstractMessageWriterResultHandler
-		implements HandlerResultHandler {
-
+public class ResponseBodyResultHandler extends AbstractMessageWriterResultHandler implements HandlerResultHandler {
 
 	/**
 	 * Basic constructor with a default {@link ReactiveAdapterRegistry}.
@@ -86,7 +83,7 @@ public class ResponseBodyResultHandler extends AbstractMessageWriterResultHandle
 
 	@Override
 	public Mono<Void> handleResult(ServerWebExchange exchange, HandlerResult result) {
-		Object body = result.getReturnValue().orElse(null);
+		Object body = result.getReturnValue();
 		MethodParameter bodyTypeParameter = result.getReturnTypeSource();
 		return writeBody(body, bodyTypeParameter, exchange);
 	}

spring-webflux/src/main/java/org/springframework/web/reactive/result/view/BindStatus.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.reactive.result.view;
 
 import java.beans.PropertyEditor;
@@ -99,7 +100,7 @@ public class BindStatus {
 			this.expression = path.substring(dotPos + 1);
 		}
 
-		this.errors = requestContext.getErrors(beanName, false).orElse(null);
+		this.errors = requestContext.getErrors(beanName, false);
 
 		if (this.errors != null) {
 			// Usual case: A BindingResult is available as request attribute.

spring-webflux/src/main/java/org/springframework/web/reactive/result/view/DefaultRendering.java

@@ -13,11 +13,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.reactive.result.view;
 
 import java.util.Collections;
 import java.util.Map;
-import java.util.Optional;
 
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
@@ -47,13 +47,13 @@ class DefaultRendering implements Rendering {
 		this.view = view;
 		this.model = (model != null ? model.asMap() : Collections.emptyMap());
 		this.status = status;
-		this.headers = headers != null ? headers : EMPTY_HEADERS;
+		this.headers = (headers != null ? headers : EMPTY_HEADERS);
 	}
 
 
 	@Override
-	public Optional<Object> view() {
-		return Optional.ofNullable(this.view);
+	public Object view() {
+		return this.view;
 	}
 
 	@Override
@@ -62,8 +62,8 @@ class DefaultRendering implements Rendering {
 	}
 
 	@Override
-	public Optional<HttpStatus> status() {
-		return Optional.ofNullable(this.status);
+	public HttpStatus status() {
+		return this.status;
 	}
 
 	@Override

spring-webflux/src/main/java/org/springframework/web/reactive/result/view/Rendering.java

@@ -13,17 +13,16 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.reactive.result.view;
 
 import java.util.Collection;
 import java.util.Map;
-import java.util.Optional;
 
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
 import org.springframework.ui.Model;
 
-
 /**
  * Public API for HTML rendering. Supported as a return value in Spring WebFlux
  * controllers. Comparable to the use of {@code ModelAndView} as a return value
@@ -46,7 +45,7 @@ public interface Rendering {
 	/**
 	 * Return the selected {@link String} view name or {@link View} object.
 	 */
-	Optional<Object> view();
+	Object view();
 
 	/**
 	 * Return attributes to add to the model.
@@ -56,7 +55,7 @@ public interface Rendering {
 	/**
 	 * Return the HTTP status to set the response to.
 	 */
-	Optional<HttpStatus> status();
+	HttpStatus status();
 
 	/**
 	 * Return headers to add to the response.

spring-webflux/src/main/java/org/springframework/web/reactive/result/view/RequestContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -19,7 +19,6 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
-import java.util.Optional;
 import java.util.TimeZone;
 
 import org.springframework.context.MessageSource;
@@ -170,8 +169,8 @@ public class RequestContext {
 	 * Return the {@link RequestDataValueProcessor} instance to apply to in form
 	 * tag libraries and to redirect URLs.
 	 */
-	public Optional<RequestDataValueProcessor> getRequestDataValueProcessor() {
-		return Optional.ofNullable(this.dataValueProcessor);
+	public RequestDataValueProcessor getRequestDataValueProcessor() {
+		return this.dataValueProcessor;
 	}
 
 	/**
@@ -346,7 +345,7 @@ public class RequestContext {
 	 * @param name name of the bind object
 	 * @return the Errors instance, or {@code null} if not found
 	 */
-	public Optional<Errors> getErrors(String name) {
+	public Errors getErrors(String name) {
 		return getErrors(name, isDefaultHtmlEscape());
 	}
 
@@ -356,34 +355,28 @@ public class RequestContext {
 	 * @param htmlEscape create an Errors instance with automatic HTML escaping?
 	 * @return the Errors instance, or {@code null} if not found
 	 */
-	public Optional<Errors> getErrors(String name, boolean htmlEscape) {
+	public Errors getErrors(String name, boolean htmlEscape) {
 		if (this.errorsMap == null) {
 			this.errorsMap = new HashMap<>();
 		}
 
-		// Since there is no Optional orElse + flatMap...
-		Optional<Errors> optional = Optional.ofNullable(this.errorsMap.get(name));
-		optional = optional.isPresent() ? optional : getModelObject(BindingResult.MODEL_KEY_PREFIX + name);
+		Errors errors = this.errorsMap.get(name);
+		if (errors == null) {
+			errors = getModelObject(BindingResult.MODEL_KEY_PREFIX + name);
+		}
+		if (errors instanceof BindException) {
+			errors = ((BindException) errors).getBindingResult();
+		}
 
-		return optional
-				.map(errors -> {
-					if (errors instanceof BindException) {
-						return ((BindException) errors).getBindingResult();
-					}
-					else {
-						return errors;
-					}
-				})
-				.map(errors -> {
-					if (htmlEscape && !(errors instanceof EscapedErrors)) {
-						errors = new EscapedErrors(errors);
-					}
-					else if (!htmlEscape && errors instanceof EscapedErrors) {
-						errors = ((EscapedErrors) errors).getSource();
-					}
-					this.errorsMap.put(name, errors);
-					return errors;
-				});
+		if (htmlEscape && !(errors instanceof EscapedErrors)) {
+			errors = new EscapedErrors(errors);
+		}
+		else if (!htmlEscape && errors instanceof EscapedErrors) {
+			errors = ((EscapedErrors) errors).getSource();
+		}
+
+		this.errorsMap.put(name, errors);
+		return errors;
 	}
 
 	/**
@@ -393,10 +386,12 @@ public class RequestContext {
 	 * @return the model object
 	 */
 	@SuppressWarnings("unchecked")
-	protected <T> Optional<T> getModelObject(String modelName) {
-		return Optional.ofNullable(this.model)
-				.map(model -> Optional.ofNullable((T) model.get(modelName)))
-				.orElse(this.exchange.getAttribute(modelName));
+	protected <T> T getModelObject(String modelName) {
+		T modelObject = (T) this.model.get(modelName);
+		if (modelObject == null) {
+			modelObject = (T) this.exchange.getAttribute(modelName);
+		}
+		return modelObject;
 	}
 
 	/**

spring-webflux/src/main/java/org/springframework/web/reactive/result/view/ViewResolutionResultHandler.java

@@ -36,9 +36,9 @@ import org.springframework.core.ReactiveAdapter;
 import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.annotation.AnnotationAwareOrderComparator;
+import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
 import org.springframework.ui.Model;
-import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 import org.springframework.validation.BindingResult;
 import org.springframework.web.bind.annotation.ModelAttribute;
@@ -56,13 +56,13 @@ import org.springframework.web.server.support.HttpRequestPathHelper;
  * {@code HandlerResultHandler} that encapsulates the view resolution algorithm
  * supporting the following return types:
  * <ul>
- *     <li>{@link Void} or no value -- default view name</li>
- *     <li>{@link String} -- view name unless {@code @ModelAttribute}-annotated
- *     <li>{@link View} -- View to render with
- *     <li>{@link Model} -- attributes to add to the model
- *     <li>{@link Map} -- attributes to add to the model
- *     <li>{@link ModelAttribute @ModelAttribute} -- attribute for the model
- *     <li>Non-simple value -- attribute for the model
+ * <li>{@link Void} or no value -- default view name</li>
+ * <li>{@link String} -- view name unless {@code @ModelAttribute}-annotated
+ * <li>{@link View} -- View to render with
+ * <li>{@link Model} -- attributes to add to the model
+ * <li>{@link Map} -- attributes to add to the model
+ * <li>{@link ModelAttribute @ModelAttribute} -- attribute for the model
+ * <li>Non-simple value -- attribute for the model
  * </ul>
  *
  * <p>A String-based view name is resolved through the configured
@@ -150,14 +150,16 @@ public class ViewResolutionResultHandler extends HandlerResultHandlerSupport
 		if (hasModelAnnotation(result.getReturnTypeSource())) {
 			return true;
 		}
+
 		Class<?> type = result.getReturnType().getRawClass();
 		ReactiveAdapter adapter = getAdapter(result);
 		if (adapter != null) {
 			if (adapter.isNoValue()) {
 				return true;
 			}
-			type = result.getReturnType().getGeneric(0).resolve(Object.class);
+			type = result.getReturnType().getGeneric().resolve(Object.class);
 		}
+
 		return (CharSequence.class.isAssignableFrom(type) || Rendering.class.isAssignableFrom(type) ||
 				Model.class.isAssignableFrom(type) || Map.class.isAssignableFrom(type) ||
 				void.class.equals(type) || View.class.isAssignableFrom(type) ||
@@ -171,22 +173,21 @@ public class ViewResolutionResultHandler extends HandlerResultHandlerSupport
 	@Override
 	@SuppressWarnings("unchecked")
 	public Mono<Void> handleResult(ServerWebExchange exchange, HandlerResult result) {
-
 		Mono<Object> valueMono;
 		ResolvableType valueType;
 		ReactiveAdapter adapter = getAdapter(result);
 
 		if (adapter != null) {
-			Assert.isTrue(!adapter.isMultiValue(), "Multi-value " +
-					"reactive types not supported in view resolution: " + result.getReturnType());
+			if (adapter.isMultiValue()) {
+				throw new IllegalArgumentException(
+						"Multi-value reactive types not supported in view resolution: " + result.getReturnType());
+			}
 
-			valueMono = result.getReturnValue()
-					.map(value -> Mono.from(adapter.toPublisher(value)))
-					.orElse(Mono.empty());
+			valueMono = (result.getReturnValue() != null ?
+					Mono.from(adapter.toPublisher(result.getReturnValue())) : Mono.empty());
 
-			valueType = adapter.isNoValue() ?
-					ResolvableType.forClass(Void.class) :
-					result.getReturnType().getGeneric(0);
+			valueType = (adapter.isNoValue() ? ResolvableType.forClass(Void.class) :
+					result.getReturnType().getGeneric());
 		}
 		else {
 			valueMono = Mono.justOrEmpty(result.getReturnValue());
@@ -217,10 +218,16 @@ public class ViewResolutionResultHandler extends HandlerResultHandlerSupport
 					}
 					else if (Rendering.class.isAssignableFrom(clazz)) {
 						Rendering render = (Rendering) returnValue;
-						render.status().ifPresent(exchange.getResponse()::setStatusCode);
+						HttpStatus status = render.status();
+						if (status != null) {
+							exchange.getResponse().setStatusCode(status);
+						}
 						exchange.getResponse().getHeaders().putAll(render.headers());
 						model.addAllAttributes(render.modelAttributes());
-						Object view = render.view().orElse(getDefaultViewName(exchange));
+						Object view = render.view();
+						if (view == null) {
+							view = getDefaultViewName(exchange);
+						}
 						viewsMono = (view instanceof String ? resolveViews((String) view, locale) :
 								Mono.just(Collections.singletonList((View) view)));
 					}

spring-webflux/src/main/java/org/springframework/web/reactive/socket/HandshakeInfo.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -13,11 +13,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.reactive.socket;
 
 import java.net.URI;
 import java.security.Principal;
-import java.util.Optional;
 
 import reactor.core.publisher.Mono;
 
@@ -32,7 +32,6 @@ import org.springframework.util.Assert;
  * @since 5.0
  * @see WebSocketSession#getHandshakeInfo()
  */
-@SuppressWarnings("OptionalUsedAsFieldOrParameterType")
 public class HandshakeInfo {
 
 	private final URI uri;
@@ -41,7 +40,7 @@ public class HandshakeInfo {
 
 	private final HttpHeaders headers;
 
-	private final Optional<String> protocol;
+	private final String protocol;
 
 
 	/**
@@ -49,13 +48,12 @@ public class HandshakeInfo {
 	 * @param uri the endpoint URL
 	 * @param headers request headers for server or response headers or client
 	 * @param principal the principal for the session
-	 * @param protocol the negotiated sub-protocol
+	 * @param protocol the negotiated sub-protocol (may be {@code null})
 	 */
-	public HandshakeInfo(URI uri, HttpHeaders headers, Mono<Principal> principal, Optional<String> protocol) {
-		Assert.notNull(uri, "URI is required.");
-		Assert.notNull(headers, "HttpHeaders are required.");
-		Assert.notNull(principal, "Principal is required.");
-		Assert.notNull(protocol, "Sub-protocol is required.");
+	public HandshakeInfo(URI uri, HttpHeaders headers, Mono<Principal> principal, String protocol) {
+		Assert.notNull(uri, "URI is required");
+		Assert.notNull(headers, "HttpHeaders are required");
+		Assert.notNull(principal, "Principal is required");
 		this.uri = uri;
 		this.headers = headers;
 		this.principalMono = principal;
@@ -86,11 +84,11 @@ public class HandshakeInfo {
 	}
 
 	/**
-	 * The sub-protocol negotiated at handshake time.
+	 * The sub-protocol negotiated at handshake time, or {@code null} if none.
 	 * @see <a href="https://tools.ietf.org/html/rfc6455#section-1.9">
-	 *     https://tools.ietf.org/html/rfc6455#section-1.9</a>
+	 * https://tools.ietf.org/html/rfc6455#section-1.9</a>
 	 */
-	public Optional<String> getSubProtocol() {
+	public String getSubProtocol() {
 		return this.protocol;
 	}
 

spring-webflux/src/main/java/org/springframework/web/reactive/socket/WebSocketHandler.java

@@ -13,8 +13,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.reactive.socket;
 
+import java.util.Collections;
+import java.util.List;
+
 import reactor.core.publisher.Mono;
 
 /**
@@ -27,10 +31,10 @@ public interface WebSocketHandler {
 
 	/**
 	 * Return the list of sub-protocols supported by this handler.
-	 * <p>By default an empty array is returned.
+	 * <p>By default an empty list is returned.
 	 */
-	default String[] getSubProtocols() {
-		return new String[0];
+	default List<String> getSubProtocols() {
+		return Collections.emptyList();
 	}
 
 	/**

spring-webflux/src/main/java/org/springframework/web/reactive/socket/client/JettyWebSocketClient.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -17,6 +17,7 @@
 package org.springframework.web.reactive.socket.client;
 
 import java.net.URI;
+import java.util.List;
 
 import org.eclipse.jetty.websocket.api.UpgradeRequest;
 import org.eclipse.jetty.websocket.api.UpgradeResponse;
@@ -154,7 +155,7 @@ public class JettyWebSocketClient extends WebSocketClientSupport implements WebS
 		MonoProcessor<Void> completionMono = MonoProcessor.create();
 		return Mono.fromCallable(
 				() -> {
-					String[] protocols = beforeHandshake(url, headers, handler);
+					List<String> protocols = beforeHandshake(url, headers, handler);
 					ClientUpgradeRequest upgradeRequest = new ClientUpgradeRequest();
 					upgradeRequest.setSubProtocols(protocols);
 					Object jettyHandler = createJettyHandler(url, handler, completionMono);

spring-webflux/src/main/java/org/springframework/web/reactive/socket/client/ReactorNettyWebSocketClient.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -16,6 +16,7 @@
 package org.springframework.web.reactive.socket.client;
 
 import java.net.URI;
+import java.util.List;
 import java.util.function.Consumer;
 
 import io.netty.buffer.ByteBufAllocator;
@@ -74,13 +75,12 @@ public class ReactorNettyWebSocketClient extends WebSocketClientSupport implemen
 
 	@Override
 	public Mono<Void> execute(URI url, HttpHeaders headers, WebSocketHandler handler) {
-
-		String[] protocols = beforeHandshake(url, headers, handler);
+		List<String> protocols = beforeHandshake(url, headers, handler);
 
 		return getHttpClient()
 				.ws(url.toString(),
 						nettyHeaders -> setNettyHeaders(headers, nettyHeaders),
-						StringUtils.arrayToCommaDelimitedString(protocols))
+						StringUtils.collectionToCommaDelimitedString(protocols))
 				.flatMap(response -> {
 					HandshakeInfo info = afterHandshake(url, toHttpHeaders(response));
 					ByteBufAllocator allocator = response.channel().alloc();

spring-webflux/src/main/java/org/springframework/web/reactive/socket/client/StandardWebSocketClient.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -17,7 +17,6 @@
 package org.springframework.web.reactive.socket.client;
 
 import java.net.URI;
-import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 import javax.websocket.ClientEndpointConfig;
@@ -94,10 +93,10 @@ public class StandardWebSocketClient extends WebSocketClientSupport implements W
 		MonoProcessor<Void> completionMono = MonoProcessor.create();
 		return Mono.fromCallable(
 				() -> {
-					String[] subProtocols = beforeHandshake(url, requestHeaders, handler);
+					List<String> protocols = beforeHandshake(url, requestHeaders, handler);
 					DefaultConfigurator configurator = new DefaultConfigurator(requestHeaders);
 					Endpoint endpoint = createEndpoint(url, handler, completionMono, configurator);
-					ClientEndpointConfig config = createEndpointConfig(configurator, subProtocols);
+					ClientEndpointConfig config = createEndpointConfig(configurator, protocols);
 					return this.webSocketContainer.connectToServer(endpoint, config, url);
 				})
 				.subscribeOn(Schedulers.elastic()) // connectToServer is blocking
@@ -114,10 +113,10 @@ public class StandardWebSocketClient extends WebSocketClientSupport implements W
 		});
 	}
 
-	private ClientEndpointConfig createEndpointConfig(Configurator configurator, String[] subProtocols) {
+	private ClientEndpointConfig createEndpointConfig(Configurator configurator, List<String> subProtocols) {
 		return ClientEndpointConfig.Builder.create()
 				.configurator(configurator)
-				.preferredSubprotocols(Arrays.asList(subProtocols))
+				.preferredSubprotocols(subProtocols)
 				.build();
 	}
 
@@ -128,12 +127,10 @@ public class StandardWebSocketClient extends WebSocketClientSupport implements W
 
 		private final HttpHeaders responseHeaders = new HttpHeaders();
 
-
 		public DefaultConfigurator(HttpHeaders requestHeaders) {
 			this.requestHeaders = requestHeaders;
 		}
 
-
 		public HttpHeaders getResponseHeaders() {
 			return this.responseHeaders;
 		}

spring-webflux/src/main/java/org/springframework/web/reactive/socket/client/UndertowWebSocketClient.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -18,7 +18,6 @@ package org.springframework.web.reactive.socket.client;
 
 import java.io.IOException;
 import java.net.URI;
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
@@ -132,18 +131,15 @@ public class UndertowWebSocketClient extends WebSocketClientSupport implements W
 		return Mono.fromCallable(
 				() -> {
 					ConnectionBuilder builder = createConnectionBuilder(url);
-					String[] protocols = beforeHandshake(url, headers, handler);
+					List<String> protocols = beforeHandshake(url, headers, handler);
 					DefaultNegotiation negotiation = new DefaultNegotiation(protocols, headers, builder);
 					builder.setClientNegotiation(negotiation);
-
 					return builder.connect().addNotifier(
 							new IoFuture.HandlingNotifier<WebSocketChannel, Object>() {
-
 								@Override
 								public void handleDone(WebSocketChannel channel, Object attachment) {
 									handleChannel(url, handler, completion, negotiation, channel);
 								}
-
 								@Override
 								public void handleFailed(IOException ex, Object attachment) {
 									completion.onError(new IllegalStateException("Failed to connect", ex));
@@ -161,11 +157,9 @@ public class UndertowWebSocketClient extends WebSocketClientSupport implements W
 	 * provided at construction time.
 	 */
 	protected ConnectionBuilder createConnectionBuilder(URI url) {
-
 		ConnectionBuilder builder = io.undertow.websockets.client.WebSocketClient
 				.connectionBuilder(getXnioWorker(),
 						new DefaultByteBufferPool(false, getPoolBufferSize()), url);
-
 		this.builderConsumer.accept(builder);
 		return builder;
 	}
@@ -192,11 +186,10 @@ public class UndertowWebSocketClient extends WebSocketClientSupport implements W
 
 		private final WebSocketClientNegotiation delegate;
 
-
-		public DefaultNegotiation(String[] protocols, HttpHeaders requestHeaders,
+		public DefaultNegotiation(List<String> protocols, HttpHeaders requestHeaders,
 				ConnectionBuilder connectionBuilder) {
 
-			super(Arrays.asList(protocols), Collections.emptyList());
+			super(protocols, Collections.emptyList());
 			this.requestHeaders = requestHeaders;
 			this.delegate = connectionBuilder.getClientNegotiation();
 		}

spring-webflux/src/main/java/org/springframework/web/reactive/socket/client/WebSocketClientSupport.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -13,10 +13,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.reactive.socket.client;
 
 import java.net.URI;
-import java.util.Optional;
+import java.util.List;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -40,7 +41,7 @@ public class WebSocketClientSupport {
 	protected final Log logger = LogFactory.getLog(getClass());
 
 
-	protected String[] beforeHandshake(URI url, HttpHeaders requestHeaders, WebSocketHandler handler) {
+	protected List<String> beforeHandshake(URI url, HttpHeaders requestHeaders, WebSocketHandler handler) {
 		if (logger.isDebugEnabled()) {
 			logger.debug("Executing handshake to " + url);
 		}
@@ -52,7 +53,7 @@ public class WebSocketClientSupport {
 			logger.debug("Handshake response: " + url + ", " + responseHeaders);
 		}
 		String protocol = responseHeaders.getFirst(SEC_WEBSOCKET_PROTOCOL);
-		return new HandshakeInfo(url, responseHeaders, Mono.empty(), Optional.ofNullable(protocol));
+		return new HandshakeInfo(url, responseHeaders, Mono.empty(), protocol);
 	}
 
-}
+}

spring-webflux/src/main/java/org/springframework/web/reactive/socket/server/RequestUpgradeStrategy.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -13,9 +13,8 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.springframework.web.reactive.socket.server;
 
-import java.util.Optional;
+package org.springframework.web.reactive.socket.server;
 
 import reactor.core.publisher.Mono;
 
@@ -46,8 +45,6 @@ public interface RequestUpgradeStrategy {
 	 * @return completion {@code Mono<Void>} to indicate the outcome of the
 	 * WebSocket session handling.
 	 */
-	@SuppressWarnings("OptionalUsedAsFieldOrParameterType")
-	Mono<Void> upgrade(ServerWebExchange exchange, WebSocketHandler webSocketHandler,
-			Optional<String> subProtocol);
+	Mono<Void> upgrade(ServerWebExchange exchange, WebSocketHandler webSocketHandler, String subProtocol);
 
 }

spring-webflux/src/main/java/org/springframework/web/reactive/socket/server/support/HandshakeWebSocketService.java

@@ -13,12 +13,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.reactive.socket.server.support;
 
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
-import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -93,7 +92,7 @@ public class HandshakeWebSocketService implements WebSocketService, Lifecycle {
 	 * @param upgradeStrategy the strategy to use
 	 */
 	public HandshakeWebSocketService(RequestUpgradeStrategy upgradeStrategy) {
-		Assert.notNull(upgradeStrategy, "'upgradeStrategy' is required");
+		Assert.notNull(upgradeStrategy, "RequestUpgradeStrategy is required");
 		this.upgradeStrategy = upgradeStrategy;
 	}
 
@@ -197,7 +196,7 @@ public class HandshakeWebSocketService implements WebSocketService, Lifecycle {
 			return handleBadRequest("Missing \"Sec-WebSocket-Key\" header");
 		}
 
-		Optional<String> protocol = selectProtocol(headers, handler);
+		String protocol = selectProtocol(headers, handler);
 		return this.upgradeStrategy.upgrade(exchange, handler, protocol);
 	}
 
@@ -208,15 +207,17 @@ public class HandshakeWebSocketService implements WebSocketService, Lifecycle {
 		return Mono.error(new ServerWebInputException(reason));
 	}
 
-	private Optional<String> selectProtocol(HttpHeaders headers, WebSocketHandler handler) {
+	private String selectProtocol(HttpHeaders headers, WebSocketHandler handler) {
 		String protocolHeader = headers.getFirst(SEC_WEBSOCKET_PROTOCOL);
-		if (protocolHeader == null) {
-			return Optional.empty();
+		if (protocolHeader != null) {
+			List<String> supportedProtocols = handler.getSubProtocols();
+			for (String protocol : StringUtils.commaDelimitedListToStringArray(protocolHeader)) {
+				if (supportedProtocols.contains(protocol)) {
+					return protocol;
+				}
+			}
 		}
-		String[] protocols = handler.getSubProtocols();
-		return StringUtils.commaDelimitedListToSet(protocolHeader).stream()
-				.filter(protocol -> Arrays.stream(protocols).anyMatch(protocol::equals))
-				.findFirst();
+		return null;
 	}
 
 }

spring-webflux/src/main/java/org/springframework/web/reactive/socket/server/upgrade/JettyRequestUpgradeStrategy.java

@@ -18,7 +18,6 @@ package org.springframework.web.reactive.socket.server.upgrade;
 
 import java.io.IOException;
 import java.security.Principal;
-import java.util.Optional;
 import javax.servlet.ServletContext;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
@@ -48,7 +47,6 @@ import org.springframework.web.server.ServerWebExchange;
  * @author Rossen Stoyanchev
  * @since 5.0
  */
-@SuppressWarnings("OptionalUsedAsFieldOrParameterType")
 public class JettyRequestUpgradeStrategy implements RequestUpgradeStrategy, Lifecycle {
 
 	private static final ThreadLocal<WebSocketHandlerContainer> adapterHolder =
@@ -73,7 +71,7 @@ public class JettyRequestUpgradeStrategy implements RequestUpgradeStrategy, Life
 					this.factory = new WebSocketServerFactory(this.servletContext);
 					this.factory.setCreator((request, response) -> {
 						WebSocketHandlerContainer container = adapterHolder.get();
-						String protocol = container.getProtocol().orElse(null);
+						String protocol = container.getProtocol();
 						if (protocol != null) {
 							response.setAcceptedSubProtocol(protocol);
 						}
@@ -110,9 +108,7 @@ public class JettyRequestUpgradeStrategy implements RequestUpgradeStrategy, Life
 
 
 	@Override
-	public Mono<Void> upgrade(ServerWebExchange exchange, WebSocketHandler handler,
-			Optional<String> subProtocol) {
-
+	public Mono<Void> upgrade(ServerWebExchange exchange, WebSocketHandler handler, String subProtocol) {
 		ServerHttpRequest request = exchange.getRequest();
 		ServerHttpResponse response = exchange.getResponse();
 
@@ -155,7 +151,7 @@ public class JettyRequestUpgradeStrategy implements RequestUpgradeStrategy, Life
 		return ((ServletServerHttpResponse) response).getServletResponse();
 	}
 
-	private HandshakeInfo getHandshakeInfo(ServerWebExchange exchange, Optional<String> protocol) {
+	private HandshakeInfo getHandshakeInfo(ServerWebExchange exchange, String protocol) {
 		ServerHttpRequest request = exchange.getRequest();
 		Mono<Principal> principal = exchange.getPrincipal();
 		return new HandshakeInfo(request.getURI(), request.getHeaders(), principal, protocol);
@@ -178,9 +174,9 @@ public class JettyRequestUpgradeStrategy implements RequestUpgradeStrategy, Life
 
 		private final JettyWebSocketHandlerAdapter adapter;
 
-		private final Optional<String> protocol;
+		private final String protocol;
 
-		public WebSocketHandlerContainer(JettyWebSocketHandlerAdapter adapter, Optional<String> protocol) {
+		public WebSocketHandlerContainer(JettyWebSocketHandlerAdapter adapter, String protocol) {
 			this.adapter = adapter;
 			this.protocol = protocol;
 		}
@@ -189,7 +185,7 @@ public class JettyRequestUpgradeStrategy implements RequestUpgradeStrategy, Life
 			return this.adapter;
 		}
 
-		public Optional<String> getProtocol() {
+		public String getProtocol() {
 			return this.protocol;
 		}
 	}

spring-webflux/src/main/java/org/springframework/web/reactive/socket/server/upgrade/ReactorNettyRequestUpgradeStrategy.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -13,10 +13,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.reactive.socket.server.upgrade;
 
 import java.security.Principal;
-import java.util.Optional;
 
 import reactor.core.publisher.Mono;
 
@@ -35,23 +35,19 @@ import org.springframework.web.server.ServerWebExchange;
  * @author Rossen Stoyanchev
  * @since 5.0
  */
-@SuppressWarnings("OptionalUsedAsFieldOrParameterType")
 public class ReactorNettyRequestUpgradeStrategy implements RequestUpgradeStrategy {
 
 	@Override
-	public Mono<Void> upgrade(ServerWebExchange exchange, WebSocketHandler handler,
-			Optional<String> subProtocol) {
-
+	public Mono<Void> upgrade(ServerWebExchange exchange, WebSocketHandler handler, String subProtocol) {
 		ReactorServerHttpResponse response = (ReactorServerHttpResponse) exchange.getResponse();
 		HandshakeInfo info = getHandshakeInfo(exchange, subProtocol);
 		NettyDataBufferFactory bufferFactory = (NettyDataBufferFactory) response.bufferFactory();
 
-		return response.getReactorResponse().sendWebsocket(subProtocol.orElse(null),
-				(in, out) -> handler.handle(
-						new ReactorNettyWebSocketSession(in, out, info, bufferFactory)));
+		return response.getReactorResponse().sendWebsocket(subProtocol,
+				(in, out) -> handler.handle(new ReactorNettyWebSocketSession(in, out, info, bufferFactory)));
 	}
 
-	private HandshakeInfo getHandshakeInfo(ServerWebExchange exchange, Optional<String> protocol) {
+	private HandshakeInfo getHandshakeInfo(ServerWebExchange exchange, String protocol) {
 		ServerHttpRequest request = exchange.getRequest();
 		Mono<Principal> principal = exchange.getPrincipal();
 		return new HandshakeInfo(request.getURI(), request.getHeaders(), principal, protocol);

spring-webflux/src/main/java/org/springframework/web/reactive/socket/server/upgrade/TomcatRequestUpgradeStrategy.java

@@ -19,7 +19,6 @@ package org.springframework.web.reactive.socket.server.upgrade;
 import java.io.IOException;
 import java.security.Principal;
 import java.util.Collections;
-import java.util.Optional;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
@@ -47,14 +46,13 @@ import org.springframework.web.server.ServerWebExchange;
  * @author Violeta Georgieva
  * @since 5.0
  */
-@SuppressWarnings("OptionalUsedAsFieldOrParameterType")
 public class TomcatRequestUpgradeStrategy implements RequestUpgradeStrategy {
 
 	private static final String SERVER_CONTAINER_ATTR = "javax.websocket.server.ServerContainer";
 
 
 	@Override
-	public Mono<Void> upgrade(ServerWebExchange exchange, WebSocketHandler handler, Optional<String> subProtocol){
+	public Mono<Void> upgrade(ServerWebExchange exchange, WebSocketHandler handler, String subProtocol){
 		ServerHttpRequest request = exchange.getRequest();
 		ServerHttpResponse response = exchange.getResponse();
 
@@ -70,7 +68,7 @@ public class TomcatRequestUpgradeStrategy implements RequestUpgradeStrategy {
 
 		String requestURI = servletRequest.getRequestURI();
 		DefaultServerEndpointConfig config = new DefaultServerEndpointConfig(requestURI, endpoint);
-		config.setSubprotocols(subProtocol.map(Collections::singletonList).orElse(Collections.emptyList()));
+		config.setSubprotocols(subProtocol != null ? Collections.singletonList(subProtocol) : Collections.emptyList());
 
 		try {
 			WsServerContainer container = getContainer(servletRequest);
@@ -93,7 +91,7 @@ public class TomcatRequestUpgradeStrategy implements RequestUpgradeStrategy {
 		return ((ServletServerHttpResponse) response).getServletResponse();
 	}
 
-	private HandshakeInfo getHandshakeInfo(ServerWebExchange exchange, Optional<String> protocol) {
+	private HandshakeInfo getHandshakeInfo(ServerWebExchange exchange, String protocol) {
 		ServerHttpRequest request = exchange.getRequest();
 		Mono<Principal> principal = exchange.getPrincipal();
 		return new HandshakeInfo(request.getURI(), request.getHeaders(), principal, protocol);

spring-webflux/src/main/java/org/springframework/web/reactive/socket/server/upgrade/UndertowRequestUpgradeStrategy.java

@@ -20,7 +20,6 @@ import java.net.URI;
 import java.security.Principal;
 import java.util.Collections;
 import java.util.List;
-import java.util.Optional;
 import java.util.Set;
 
 import io.undertow.server.HttpServerExchange;
@@ -50,16 +49,15 @@ import org.springframework.web.server.ServerWebExchange;
  * @author Violeta Georgieva
  * @since 5.0
  */
-@SuppressWarnings("OptionalUsedAsFieldOrParameterType")
 public class UndertowRequestUpgradeStrategy implements RequestUpgradeStrategy {
 
 	@Override
-	public Mono<Void> upgrade(ServerWebExchange exchange, WebSocketHandler handler, Optional<String> subProtocol) {
+	public Mono<Void> upgrade(ServerWebExchange exchange, WebSocketHandler handler, String subProtocol) {
 		ServerHttpRequest request = exchange.getRequest();
 		Assert.isInstanceOf(UndertowServerHttpRequest.class, request, "UndertowServerHttpRequest required");
 		HttpServerExchange httpExchange = ((UndertowServerHttpRequest) request).getUndertowExchange();
 
-		Set<String> protocols = subProtocol.map(Collections::singleton).orElse(Collections.emptySet());
+		Set<String> protocols = (subProtocol != null ? Collections.singleton(subProtocol) : Collections.emptySet());
 		Hybi13Handshake handshake = new Hybi13Handshake(protocols, false);
 		List<Handshake> handshakes = Collections.singletonList(handshake);
 

spring-webflux/src/test/java/org/springframework/web/reactive/config/DelegatingWebFluxConfigurationTests.java

@@ -18,7 +18,6 @@ package org.springframework.web.reactive.config;
 
 import java.util.Collections;
 import java.util.List;
-import java.util.Optional;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -37,13 +36,8 @@ import org.springframework.web.bind.support.ConfigurableWebBindingInitializer;
 import org.springframework.web.reactive.accept.RequestedContentTypeResolverBuilder;
 import org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerAdapter;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertSame;
-import static org.junit.Assert.assertTrue;
-import static org.mockito.BDDMockito.any;
-import static org.mockito.BDDMockito.doAnswer;
-import static org.mockito.BDDMockito.given;
-import static org.mockito.BDDMockito.verify;
+import static org.junit.Assert.*;
+import static org.mockito.BDDMockito.*;
 
 /**
  * Test fixture for {@link DelegatingWebFluxConfiguration} tests.
@@ -72,8 +66,8 @@ public class DelegatingWebFluxConfigurationTests {
 		MockitoAnnotations.initMocks(this);
 		delegatingConfig = new DelegatingWebFluxConfiguration();
 		delegatingConfig.setApplicationContext(new StaticApplicationContext());
-		given(webFluxConfigurer.getValidator()).willReturn(Optional.empty());
-		given(webFluxConfigurer.getMessageCodesResolver()).willReturn(Optional.empty());
+		given(webFluxConfigurer.getValidator()).willReturn(null);
+		given(webFluxConfigurer.getMessageCodesResolver()).willReturn(null);
 	}
 
 

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

@@ -98,18 +98,18 @@ public class SseHandlerFunctionIntegrationTests extends AbstractRouterFunctionIn
 
 		StepVerifier.create(result)
 				.consumeNextWith( event -> {
-					assertEquals("0", event.id().get());
-					assertEquals("foo", event.data().get());
-					assertEquals("bar", event.comment().get());
-					assertFalse(event.event().isPresent());
-					assertFalse(event.retry().isPresent());
+					assertEquals("0", event.id());
+					assertEquals("foo", event.data());
+					assertEquals("bar", event.comment());
+					assertNull(event.event());
+					assertNull(event.retry());
 				})
 				.consumeNextWith( event -> {
-					assertEquals("1", event.id().get());
-					assertEquals("foo", event.data().get());
-					assertEquals("bar", event.comment().get());
-					assertFalse(event.event().isPresent());
-					assertFalse(event.retry().isPresent());
+					assertEquals("1", event.id());
+					assertEquals("foo", event.data());
+					assertEquals("bar", event.comment());
+					assertNull(event.event());
+					assertNull(event.retry());
 				})
 				.expectComplete()
 				.verify(Duration.ofSeconds(5L));

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/InvocableHandlerMethodTests.java

@@ -18,7 +18,6 @@ package org.springframework.web.reactive.result.method;
 
 import java.lang.reflect.Method;
 import java.util.Arrays;
-import java.util.Optional;
 
 import org.junit.Test;
 import reactor.core.publisher.Mono;
@@ -59,7 +58,6 @@ public class InvocableHandlerMethodTests {
 
 	@Test
 	public void invokeMethodWithNoValue() throws Exception {
-
 		Mono<Object> resolvedValue = Mono.empty();
 		Method method = on(TestController.class).mockCall(o -> o.singleArg(null)).method();
 		Mono<HandlerResult> mono = invoke(new TestController(), method, resolverFor(resolvedValue));
@@ -69,7 +67,6 @@ public class InvocableHandlerMethodTests {
 
 	@Test
 	public void invokeMethodWithValue() throws Exception {
-
 		Mono<Object> resolvedValue = Mono.just("value1");
 		Method method = on(TestController.class).mockCall(o -> o.singleArg(null)).method();
 		Mono<HandlerResult> mono = invoke(new TestController(), method, resolverFor(resolvedValue));
@@ -79,7 +76,6 @@ public class InvocableHandlerMethodTests {
 
 	@Test
 	public void noMatchingResolver() throws Exception {
-
 		Method method = on(TestController.class).mockCall(o -> o.singleArg(null)).method();
 		Mono<HandlerResult> mono = invoke(new TestController(), method);
 
@@ -95,7 +91,6 @@ public class InvocableHandlerMethodTests {
 
 	@Test
 	public void resolverThrowsException() throws Exception {
-
 		Mono<Object> resolvedValue = Mono.error(new UnsupportedMediaTypeStatusException("boo"));
 		Method method = on(TestController.class).mockCall(o -> o.singleArg(null)).method();
 		Mono<HandlerResult> mono = invoke(new TestController(), method, resolverFor(resolvedValue));
@@ -111,7 +106,6 @@ public class InvocableHandlerMethodTests {
 
 	@Test
 	public void illegalArgumentExceptionIsWrappedWithInvocationDetails() throws Exception {
-
 		Mono<Object> resolvedValue = Mono.just(1);
 		Method method = on(TestController.class).mockCall(o -> o.singleArg(null)).method();
 		Mono<HandlerResult> mono = invoke(new TestController(), method, resolverFor(resolvedValue));
@@ -129,7 +123,6 @@ public class InvocableHandlerMethodTests {
 
 	@Test
 	public void invocationTargetExceptionIsUnwrapped() throws Exception {
-
 		Method method = on(TestController.class).mockCall(TestController::exceptionMethod).method();
 		Mono<HandlerResult> mono = invoke(new TestController(), method);
 
@@ -144,7 +137,6 @@ public class InvocableHandlerMethodTests {
 
 	@Test
 	public void invokeMethodWithResponseStatus() throws Exception {
-
 		Method method = on(TestController.class).annotPresent(ResponseStatus.class).resolveMethod();
 		Mono<HandlerResult> mono = invoke(new TestController(), method);
 
@@ -175,9 +167,7 @@ public class InvocableHandlerMethodTests {
 	private void assertHandlerResultValue(Mono<HandlerResult> mono, String expected) {
 		StepVerifier.create(mono)
 				.consumeNextWith(result -> {
-					Optional<?> optional = result.getReturnValue();
-					assertTrue(optional.isPresent());
-					assertEquals(expected, optional.get());
+					assertEquals(expected, result.getReturnValue());
 				})
 				.expectComplete()
 				.verify();

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/RequestMappingInfoHandlerMappingTests.java

@@ -23,7 +23,6 @@ import java.util.Collections;
 import java.util.EnumSet;
 import java.util.HashSet;
 import java.util.Map;
-import java.util.Optional;
 import java.util.Set;
 import java.util.function.Consumer;
 
@@ -353,10 +352,10 @@ public class RequestMappingInfoHandlerMappingTests {
 		HandlerResult result = mono.block();
 		assertNotNull(result);
 
-		Optional<Object> value = result.getReturnValue();
-		assertTrue(value.isPresent());
-		assertEquals(HttpHeaders.class, value.get().getClass());
-		assertEquals(allowedMethods, ((HttpHeaders) value.get()).getAllow());
+		Object value = result.getReturnValue();
+		assertNotNull(value);
+		assertEquals(HttpHeaders.class, value.getClass());
+		assertEquals(allowedMethods, ((HttpHeaders) value).getAllow());
 	}
 
 	private void testMediaTypeNotAcceptable(String url) throws Exception {
@@ -490,4 +489,4 @@ public class RequestMappingInfoHandlerMappingTests {
 		}
 	}
 
-}
+}

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/ControllerAdviceTests.java

@@ -91,7 +91,7 @@ public class ControllerAdviceTests {
 		TestController controller = context.getBean(TestController.class);
 		controller.setException(exception);
 
-		Object actual = handle(adapter, controller, "handle").getReturnValue().orElse(null);
+		Object actual = handle(adapter, controller, "handle").getReturnValue();
 		assertEquals(expected, actual);
 	}
 

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/SseIntegrationTests.java

@@ -37,12 +37,10 @@ import org.springframework.web.reactive.config.EnableWebFlux;
 import org.springframework.web.reactive.function.client.WebClient;
 import org.springframework.web.server.adapter.WebHttpHandlerBuilder;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.springframework.core.ResolvableType.forClassWithGenerics;
-import static org.springframework.http.MediaType.TEXT_EVENT_STREAM;
-import static org.springframework.web.reactive.function.BodyExtractors.toFlux;
-
+import static org.junit.Assert.*;
+import static org.springframework.core.ResolvableType.*;
+import static org.springframework.http.MediaType.*;
+import static org.springframework.web.reactive.function.BodyExtractors.*;
 
 /**
  * @author Sebastien Deleuze
@@ -112,18 +110,18 @@ public class SseIntegrationTests extends AbstractHttpHandlerIntegrationTests {
 
 		StepVerifier.create(result)
 				.consumeNextWith( event -> {
-					assertEquals("0", event.id().get());
-					assertEquals("foo", event.data().get());
-					assertEquals("bar", event.comment().get());
-					assertFalse(event.event().isPresent());
-					assertFalse(event.retry().isPresent());
+					assertEquals("0", event.id());
+					assertEquals("foo", event.data());
+					assertEquals("bar", event.comment());
+					assertNull(event.event());
+					assertNull(event.retry());
 				})
 				.consumeNextWith( event -> {
-					assertEquals("1", event.id().get());
-					assertEquals("foo", event.data().get());
-					assertEquals("bar", event.comment().get());
-					assertFalse(event.event().isPresent());
-					assertFalse(event.retry().isPresent());
+					assertEquals("1", event.id());
+					assertEquals("foo", event.data());
+					assertEquals("bar", event.comment());
+					assertNull(event.event());
+					assertNull(event.retry());
 				})
 				.thenCancel()
 				.verify(Duration.ofSeconds(5L));
@@ -140,18 +138,18 @@ public class SseIntegrationTests extends AbstractHttpHandlerIntegrationTests {
 
 		StepVerifier.create(result)
 				.consumeNextWith( event -> {
-					assertEquals("0", event.id().get());
-					assertEquals("foo", event.data().get());
-					assertEquals("bar", event.comment().get());
-					assertFalse(event.event().isPresent());
-					assertFalse(event.retry().isPresent());
+					assertEquals("0", event.id());
+					assertEquals("foo", event.data());
+					assertEquals("bar", event.comment());
+					assertNull(event.event());
+					assertNull(event.retry());
 				})
 				.consumeNextWith( event -> {
-					assertEquals("1", event.id().get());
-					assertEquals("foo", event.data().get());
-					assertEquals("bar", event.comment().get());
-					assertFalse(event.event().isPresent());
-					assertFalse(event.retry().isPresent());
+					assertEquals("1", event.id());
+					assertEquals("foo", event.data());
+					assertEquals("bar", event.comment());
+					assertNull(event.event());
+					assertNull(event.retry());
 				})
 				.thenCancel()
 				.verify(Duration.ofSeconds(5L));

spring-webflux/src/test/java/org/springframework/web/reactive/result/view/DefaultRenderingBuilderTests.java

@@ -13,9 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.reactive.result.view;
 
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.Map;
@@ -23,29 +23,23 @@ import java.util.Map;
 import org.junit.Test;
 
 import org.springframework.http.HttpHeaders;
-import org.springframework.ui.ExtendedModelMap;
-import org.springframework.ui.Model;
-
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertNull;
-import static org.junit.Assert.assertTrue;
 
+import static org.junit.Assert.*;
 
 /**
  * Unit tests for {@link DefaultRenderingBuilder}.
+ *
  * @author Rossen Stoyanchev
  */
 public class DefaultRenderingBuilderTests {
 
-
 	@Test
 	public void defaultValues() {
 		Rendering rendering = Rendering.view("abc").build();
 
-		assertEquals("abc", rendering.view().orElse(null));
+		assertEquals("abc", rendering.view());
 		assertEquals(Collections.emptyMap(), rendering.modelAttributes());
-		assertNull(rendering.status().orElse(null));
+		assertNull(rendering.status());
 		assertEquals(0, rendering.headers().size());
 	}
 
@@ -53,7 +47,7 @@ public class DefaultRenderingBuilderTests {
 	public void defaultValuesForRedirect() throws Exception {
 		Rendering rendering = Rendering.redirectTo("abc").build();
 
-		Object view = rendering.view().orElse(null);
+		Object view = rendering.view();
 		assertEquals(RedirectView.class, view.getClass());
 		assertEquals("abc", ((RedirectView) view).getUrl());
 		assertTrue(((RedirectView) view).isContextRelative());
@@ -64,7 +58,7 @@ public class DefaultRenderingBuilderTests {
 	@Test
 	public void viewName() {
 		Rendering rendering = Rendering.view("foo").build();
-		assertEquals("foo", rendering.view().orElse(null));
+		assertEquals("foo", rendering.view());
 	}
 
 	@Test
@@ -118,7 +112,7 @@ public class DefaultRenderingBuilderTests {
 	public void redirectWithAbsoluteUrl() throws Exception {
 		Rendering rendering = Rendering.redirectTo("foo").contextRelative(false).build();
 
-		Object view = rendering.view().orElse(null);
+		Object view = rendering.view();
 		assertEquals(RedirectView.class, view.getClass());
 		assertFalse(((RedirectView) view).isContextRelative());
 	}
@@ -127,7 +121,7 @@ public class DefaultRenderingBuilderTests {
 	public void redirectWithPropagateQuery() throws Exception {
 		Rendering rendering = Rendering.redirectTo("foo").propagateQuery(true).build();
 
-		Object view = rendering.view().orElse(null);
+		Object view = rendering.view();
 		assertEquals(RedirectView.class, view.getClass());
 		assertTrue(((RedirectView) view).isPropagateQuery());
 	}

spring-webflux/src/test/java/org/springframework/web/reactive/socket/WebSocketIntegrationTests.java

@@ -17,7 +17,9 @@
 package org.springframework.web.reactive.socket;
 
 import java.time.Duration;
+import java.util.Collections;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicReference;
 
@@ -69,19 +71,16 @@ public class WebSocketIntegrationTests extends AbstractWebSocketIntegrationTests
 
 	@Test
 	public void subProtocol() throws Exception {
-
 		String protocol = "echo-v1";
 		AtomicReference<HandshakeInfo> infoRef = new AtomicReference<>();
 		MonoProcessor<Object> output = MonoProcessor.create();
 
 		client.execute(getUrl("/sub-protocol"),
 				new WebSocketHandler() {
-
 					@Override
-					public String[] getSubProtocols() {
-						return new String[] {protocol};
+					public List<String> getSubProtocols() {
+						return Collections.singletonList(protocol);
 					}
-
 					@Override
 					public Mono<Void> handle(WebSocketSession session) {
 						infoRef.set(session.getHandshakeInfo());
@@ -96,7 +95,7 @@ public class WebSocketIntegrationTests extends AbstractWebSocketIntegrationTests
 		HandshakeInfo info = infoRef.get();
 		assertThat(info.getHeaders().getFirst("Upgrade"), Matchers.equalToIgnoringCase("websocket"));
 		assertEquals(protocol, info.getHeaders().getFirst("Sec-WebSocket-Protocol"));
-		assertEquals("Wrong protocol accepted", protocol, info.getSubProtocol().orElse("none"));
+		assertEquals("Wrong protocol accepted", protocol, info.getSubProtocol());
 		assertEquals("Wrong protocol detected on the server side", protocol, output.block(Duration.ofMillis(5000)));
 	}
 
@@ -122,7 +121,6 @@ public class WebSocketIntegrationTests extends AbstractWebSocketIntegrationTests
 
 		@Bean
 		public HandlerMapping handlerMapping() {
-
 			Map<String, WebSocketHandler> map = new HashMap<>();
 			map.put("/echo", new EchoWebSocketHandler());
 			map.put("/sub-protocol", new SubProtocolWebSocketHandler());
@@ -149,13 +147,13 @@ public class WebSocketIntegrationTests extends AbstractWebSocketIntegrationTests
 	private static class SubProtocolWebSocketHandler implements WebSocketHandler {
 
 		@Override
-		public String[] getSubProtocols() {
-			return new String[] {"echo-v1"};
+		public List<String> getSubProtocols() {
+			return Collections.singletonList("echo-v1");
 		}
 
 		@Override
 		public Mono<Void> handle(WebSocketSession session) {
-			String protocol = session.getHandshakeInfo().getSubProtocol().orElse("none");
+			String protocol = session.getHandshakeInfo().getSubProtocol();
 			WebSocketMessage message = session.textMessage(protocol);
 			return doSend(session, Mono.just(message));
 		}

spring-webflux/src/test/java/org/springframework/web/reactive/socket/client/RxNettyWebSocketClient.java

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.reactive.socket.client;
 
 import java.net.URI;
@@ -24,6 +25,7 @@ import java.util.function.Function;
 
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufAllocator;
+import io.reactivex.netty.protocol.http.HttpHandlerNames;
 import io.reactivex.netty.protocol.http.client.HttpClient;
 import io.reactivex.netty.protocol.http.client.HttpClientRequest;
 import io.reactivex.netty.protocol.http.ws.WebSocketConnection;
@@ -39,12 +41,11 @@ import rx.RxReactiveStreams;
 import org.springframework.core.io.buffer.NettyDataBufferFactory;
 import org.springframework.http.HttpHeaders;
 import org.springframework.util.ObjectUtils;
+import org.springframework.util.StringUtils;
 import org.springframework.web.reactive.socket.HandshakeInfo;
 import org.springframework.web.reactive.socket.WebSocketHandler;
 import org.springframework.web.reactive.socket.adapter.RxNettyWebSocketSession;
 
-import static io.reactivex.netty.protocol.http.HttpHandlerNames.WsClientDecoder;
-
 /**
  * {@link WebSocketClient} implementation for use with RxNetty.
  * For internal use within the framework.
@@ -125,7 +126,7 @@ public class RxNettyWebSocketClient extends WebSocketClientSupport implements We
 
 	@SuppressWarnings("cast")
 	private Observable<Void> executeInternal(URI url, HttpHeaders headers, WebSocketHandler handler) {
-		String[] protocols = beforeHandshake(url, headers, handler);
+		List<String> protocols = beforeHandshake(url, headers, handler);
 		return createRequest(url, headers, protocols)
 				.flatMap(response -> {
 					Observable<WebSocketConnection> conn = response.getWebSocketConnection();
@@ -141,13 +142,13 @@ public class RxNettyWebSocketClient extends WebSocketClientSupport implements We
 					ByteBufAllocator allocator = response.unsafeNettyChannel().alloc();
 					NettyDataBufferFactory factory = new NettyDataBufferFactory(allocator);
 					RxNettyWebSocketSession session = new RxNettyWebSocketSession(conn, info, factory);
-					session.aggregateFrames(response.unsafeNettyChannel(), WsClientDecoder.getName());
+					session.aggregateFrames(response.unsafeNettyChannel(), HttpHandlerNames.WsClientDecoder.getName());
 
 					return RxReactiveStreams.toObservable(handler.handle(session));
 				});
 	}
 
-	private WebSocketRequest<ByteBuf> createRequest(URI url, HttpHeaders headers, String[] protocols) {
+	private WebSocketRequest<ByteBuf> createRequest(URI url, HttpHeaders headers, List<String> protocols) {
 		String query = url.getRawQuery();
 		String requestUrl = url.getRawPath() + (query != null ? "?" + query : "");
 		HttpClientRequest<ByteBuf, ByteBuf> request = getHttpClient(url).createGet(requestUrl);
@@ -158,9 +159,8 @@ public class RxNettyWebSocketClient extends WebSocketClientSupport implements We
 			request = request.setHeaders(map);
 		}
 
-		return (ObjectUtils.isEmpty(protocols) ?
-				request.requestWebSocketUpgrade() :
-				request.requestWebSocketUpgrade().requestSubProtocols(protocols));
+		return (ObjectUtils.isEmpty(protocols) ? request.requestWebSocketUpgrade() :
+				request.requestWebSocketUpgrade().requestSubProtocols(StringUtils.toStringArray(protocols)));
 	}
 
 	private HttpHeaders toHttpHeaders(WebSocketResponse<ByteBuf> response) {

spring-webflux/src/test/java/org/springframework/web/reactive/socket/server/upgrade/RxNettyRequestUpgradeStrategy.java

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.reactive.socket.server.upgrade;
 
 import java.security.Principal;
@@ -40,14 +41,10 @@ import org.springframework.web.server.ServerWebExchange;
  * @author Rossen Stoyanchev
  * @since 5.0
  */
-@SuppressWarnings("OptionalUsedAsFieldOrParameterType")
 public class RxNettyRequestUpgradeStrategy implements RequestUpgradeStrategy {
 
-
 	@Override
-	public Mono<Void> upgrade(ServerWebExchange exchange, WebSocketHandler handler,
-			Optional<String> subProtocol) {
-
+	public Mono<Void> upgrade(ServerWebExchange exchange, WebSocketHandler handler, String subProtocol) {
 		RxNettyServerHttpResponse response = (RxNettyServerHttpResponse) exchange.getResponse();
 		HttpServerResponse<?> rxNettyResponse = response.getRxNettyResponse();
 
@@ -62,18 +59,18 @@ public class RxNettyRequestUpgradeStrategy implements RequestUpgradeStrategy {
 					return RxReactiveStreams.toObservable(handler.handle(session));
 				});
 
-		if (subProtocol.isPresent()) {
-			handshaker = handshaker.subprotocol(subProtocol.get());
+		if (subProtocol != null) {
+			handshaker = handshaker.subprotocol(subProtocol);
 		}
 		else {
 			// TODO: https://github.com/reactor/reactor-netty/issues/20
-			handshaker = handshaker.subprotocol(new String[0]);
+			handshaker = handshaker.subprotocol();
 		}
 
 		return Mono.from(RxReactiveStreams.toPublisher(handshaker));
 	}
 
-	private HandshakeInfo getHandshakeInfo(ServerWebExchange exchange, Optional<String> protocol) {
+	private HandshakeInfo getHandshakeInfo(ServerWebExchange exchange, String protocol) {
 		ServerHttpRequest request = exchange.getRequest();
 		Mono<Principal> principal = exchange.getPrincipal();
 		return new HandshakeInfo(request.getURI(), request.getHeaders(), principal, protocol);