Provide simple way to create ServerRequest

This commit introduces support for creating a new `ServerRequest` from
an existing instance. This is especially useful when filtering requests
in a HandlerFilterFunction.

Issue: SPR-16707

spring-test/src/main/java/org/springframework/mock/web/reactive/function/server/MockServerRequest.java

@@ -40,6 +40,7 @@ import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpRange;
 import org.springframework.http.HttpRequest;
 import org.springframework.http.MediaType;
+import org.springframework.http.codec.HttpMessageReader;
 import org.springframework.http.codec.multipart.Part;
 import org.springframework.http.server.PathContainer;
 import org.springframework.http.server.RequestPath;
@@ -50,7 +51,9 @@ import org.springframework.util.CollectionUtils;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.reactive.function.BodyExtractor;
+import org.springframework.web.reactive.function.server.HandlerStrategies;
 import org.springframework.web.reactive.function.server.ServerRequest;
+import org.springframework.web.server.ServerWebExchange;
 import org.springframework.web.server.WebSession;
 import org.springframework.web.util.UriBuilder;
 import org.springframework.web.util.UriComponentsBuilder;
@@ -91,12 +94,18 @@ public class MockServerRequest implements ServerRequest {
 	@Nullable
 	private final InetSocketAddress remoteAddress;
 
+	private final List<HttpMessageReader<?>> messageReaders;
+
+	@Nullable
+	private final ServerWebExchange exchange;
+
 
 	private MockServerRequest(HttpMethod method, URI uri, String contextPath, MockHeaders headers,
 			MultiValueMap<String, HttpCookie> cookies, @Nullable Object body,
 			Map<String, Object> attributes, MultiValueMap<String, String> queryParams,
 			Map<String, String> pathVariables, @Nullable WebSession session, @Nullable Principal principal,
-			@Nullable InetSocketAddress remoteAddress) {
+			@Nullable InetSocketAddress remoteAddress, List<HttpMessageReader<?>> messageReaders,
+			@Nullable ServerWebExchange exchange) {
 
 		this.method = method;
 		this.uri = uri;
@@ -110,6 +119,8 @@ public class MockServerRequest implements ServerRequest {
 		this.session = session;
 		this.principal = principal;
 		this.remoteAddress = remoteAddress;
+		this.messageReaders = messageReaders;
+		this.exchange = exchange;
 	}
 
 
@@ -153,6 +164,11 @@ public class MockServerRequest implements ServerRequest {
 		return Optional.ofNullable(this.remoteAddress);
 	}
 
+	@Override
+	public List<HttpMessageReader<?>> messageReaders() {
+		return this.messageReaders;
+	}
+
 	@Override
 	@SuppressWarnings("unchecked")
 	public <S> S body(BodyExtractor<S, ? super ServerHttpRequest> extractor) {
@@ -220,7 +236,6 @@ public class MockServerRequest implements ServerRequest {
 		return Mono.justOrEmpty(this.principal);
 	}
 
-
 	@Override
 	@SuppressWarnings("unchecked")
 	public Mono<MultiValueMap<String, String>> formData() {
@@ -235,6 +250,12 @@ public class MockServerRequest implements ServerRequest {
 		return (Mono<MultiValueMap<String, Part>>) this.body;
 	}
 
+	@Override
+	public ServerWebExchange exchange() {
+		Assert.state(this.exchange != null, "No exchange");
+		return this.exchange;
+	}
+
 	public static Builder builder() {
 		return new BuilderImpl();
 	}
@@ -282,6 +303,10 @@ public class MockServerRequest implements ServerRequest {
 
 		Builder remoteAddress(InetSocketAddress remoteAddress);
 
+		Builder messageReaders(List<HttpMessageReader<?>> messageReaders);
+
+		Builder exchange(ServerWebExchange exchange);
+
 		MockServerRequest body(Object body);
 
 		MockServerRequest build();
@@ -318,6 +343,11 @@ public class MockServerRequest implements ServerRequest {
 		@Nullable
 		private InetSocketAddress remoteAddress;
 
+		private List<HttpMessageReader<?>> messageReaders = HandlerStrategies.withDefaults().messageReaders();
+
+		@Nullable
+		private ServerWebExchange exchange;
+
 		@Override
 		public Builder method(HttpMethod method) {
 			Assert.notNull(method, "'method' must not be null");
@@ -440,19 +470,35 @@ public class MockServerRequest implements ServerRequest {
 			return this;
 		}
 
+		@Override
+		public Builder messageReaders(List<HttpMessageReader<?>> messageReaders) {
+			Assert.notNull(messageReaders, "'messageReaders' must not be null");
+			this.messageReaders = messageReaders;
+			return this;
+		}
+
+		@Override
+		public Builder exchange(ServerWebExchange exchange) {
+			Assert.notNull(exchange, "'exchange' must not be null");
+			this.exchange = exchange;
+			return this;
+		}
+
 		@Override
 		public MockServerRequest body(Object body) {
 			this.body = body;
 			return new MockServerRequest(this.method, this.uri, this.contextPath, this.headers,
 					this.cookies, this.body, this.attributes, this.queryParams, this.pathVariables,
-					this.session, this.principal, this.remoteAddress);
+					this.session, this.principal, this.remoteAddress, this.messageReaders,
+					this.exchange);
 		}
 
 		@Override
 		public MockServerRequest build() {
 			return new MockServerRequest(this.method, this.uri, this.contextPath, this.headers,
 					this.cookies, null, this.attributes, this.queryParams, this.pathVariables,
-					this.session, this.principal, this.remoteAddress);
+					this.session, this.principal, this.remoteAddress, this.messageReaders,
+					this.exchange);
 		}
 	}
 

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

@@ -120,6 +120,11 @@ class DefaultServerRequest implements ServerRequest {
 		return Optional.ofNullable(request().getRemoteAddress());
 	}
 
+	@Override
+	public List<HttpMessageReader<?>> messageReaders() {
+		return this.messageReaders;
+	}
+
 	@Override
 	public <T> T body(BodyExtractor<T, ? super ServerHttpRequest> extractor) {
 		return body(extractor, Collections.emptyMap());
@@ -208,7 +213,8 @@ class DefaultServerRequest implements ServerRequest {
 		return this.exchange.getRequest();
 	}
 
-	ServerWebExchange exchange() {
+	@Override
+	public ServerWebExchange exchange() {
 		return this.exchange;
 	}
 

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

+/*
+ * Copyright 2002-2018 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web.reactive.function.server;
+
+import java.net.URI;
+import java.nio.charset.StandardCharsets;
+import java.security.Principal;
+import java.time.Instant;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Consumer;
+import java.util.function.Function;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.i18n.LocaleContext;
+import org.springframework.core.ResolvableType;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.core.io.buffer.DataBufferFactory;
+import org.springframework.core.io.buffer.DataBufferUtils;
+import org.springframework.core.io.buffer.DefaultDataBufferFactory;
+import org.springframework.http.HttpCookie;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.InvalidMediaTypeException;
+import org.springframework.http.MediaType;
+import org.springframework.http.codec.HttpMessageReader;
+import org.springframework.http.codec.multipart.Part;
+import org.springframework.http.server.RequestPath;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+import org.springframework.http.server.reactive.ServerHttpResponse;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+import org.springframework.util.CollectionUtils;
+import org.springframework.util.LinkedMultiValueMap;
+import org.springframework.util.MultiValueMap;
+import org.springframework.util.StringUtils;
+import org.springframework.web.server.ServerWebExchange;
+import org.springframework.web.server.WebSession;
+import org.springframework.web.util.UriUtils;
+
+/**
+ * Default {@link ServerRequest.Builder} implementation.
+ *
+ * @author Arjen Poutsma
+ * @since 5.1
+ */
+class DefaultServerRequestBuilder implements ServerRequest.Builder {
+
+	private final HttpHeaders headers = new HttpHeaders();
+
+	private final MultiValueMap<String, HttpCookie> cookies = new LinkedMultiValueMap<>();
+
+	private final Map<String, Object> attributes = new LinkedHashMap<>();
+
+	private final List<HttpMessageReader<?>> messageReaders;
+
+	private ServerWebExchange exchange;
+
+	private HttpMethod method = HttpMethod.GET;
+
+	@Nullable
+	private URI uri;
+
+	private Flux<DataBuffer> body = Flux.empty();
+
+	public DefaultServerRequestBuilder(ServerRequest other) {
+		Assert.notNull(other, "ServerRequest must not be null");
+		this.messageReaders = other.messageReaders();
+		this.exchange = other.exchange();
+		method(other.method());
+		uri(other.uri());
+		headers(headers -> headers.addAll(other.headers().asHttpHeaders()));
+		cookies(cookies -> cookies.addAll(other.cookies()));
+	}
+
+	@Override
+	public ServerRequest.Builder method(HttpMethod method) {
+		Assert.notNull(method, "'method' must not be null");
+		this.method = method;
+		return this;
+	}
+
+	@Override
+	public ServerRequest.Builder uri(URI uri) {
+		Assert.notNull(uri, "'uri' must not be null");
+		this.uri = uri;
+		return this;
+	}
+
+	@Override
+	public ServerRequest.Builder header(String headerName, String... headerValues) {
+		for (String headerValue : headerValues) {
+			this.headers.add(headerName, headerValue);
+		}
+		return this;
+	}
+
+	@Override
+	public ServerRequest.Builder headers(Consumer<HttpHeaders> headersConsumer) {
+		Assert.notNull(headersConsumer, "'headersConsumer' must not be null");
+		headersConsumer.accept(this.headers);
+		return this;
+	}
+
+	@Override
+	public ServerRequest.Builder cookie(String name, String... values) {
+		for (String value : values) {
+			this.cookies.add(name, new HttpCookie(name, value));
+		}
+		return this;
+	}
+
+	@Override
+	public ServerRequest.Builder cookies(
+			Consumer<MultiValueMap<String, HttpCookie>> cookiesConsumer) {
+
+		Assert.notNull(cookiesConsumer, "'cookiesConsumer' must not be null");
+		cookiesConsumer.accept(this.cookies);
+		return this;
+	}
+
+	@Override
+	public ServerRequest.Builder body(Flux<DataBuffer> body) {
+		Assert.notNull(body, "'body' must not be null");
+		releaseBody();
+		this.body = body;
+		return this;
+	}
+
+	@Override
+	public ServerRequest.Builder body(String body) {
+		Assert.notNull(body, "'body' must not be null");
+		releaseBody();
+		DataBufferFactory dataBufferFactory = new DefaultDataBufferFactory();
+		this.body = Flux.just(body).
+				map(s -> {
+					byte[] bytes = body.getBytes(StandardCharsets.UTF_8);
+					return dataBufferFactory.wrap(bytes);
+				});
+		return this;
+	}
+
+	private void releaseBody() {
+		this.body.subscribe(DataBufferUtils.releaseConsumer());
+	}
+
+	@Override
+	public ServerRequest.Builder attribute(String name, Object value) {
+		Assert.notNull(name, "'name' must not be null");
+		this.attributes.put(name, value);
+		return this;
+	}
+
+	@Override
+	public ServerRequest.Builder attributes(Consumer<Map<String, Object>> attributesConsumer) {
+		Assert.notNull(attributesConsumer, "'attributesConsumer' must not be null");
+		attributesConsumer.accept(this.attributes);
+		return this;
+	}
+
+	@Override
+	public ServerRequest build() {
+		ServerHttpRequest serverHttpRequest = new BuiltServerHttpRequest(this.method, this.uri,
+				this.headers, this.cookies, this.body);
+		ServerWebExchange exchange = new DelegatingServerWebExchange(serverHttpRequest,
+				this.exchange, this.messageReaders);
+		return new DefaultServerRequest(exchange, this.messageReaders);
+	}
+
+	private static class BuiltServerHttpRequest implements ServerHttpRequest {
+
+		private static final Pattern QUERY_PATTERN = Pattern.compile("([^&=]+)(=?)([^&]+)?");
+
+
+		private final HttpMethod method;
+
+		private final URI uri;
+
+		private final RequestPath path;
+
+		private final MultiValueMap<String, String> queryParams;
+
+		private final HttpHeaders headers;
+
+		private final MultiValueMap<String, HttpCookie> cookies;
+
+		private final Flux<DataBuffer> body;
+
+		public BuiltServerHttpRequest(HttpMethod method, URI uri,
+				HttpHeaders headers,
+				MultiValueMap<String, HttpCookie> cookies,
+				Flux<DataBuffer> body) {
+			this.method = method;
+			this.uri = uri;
+			this.path = RequestPath.parse(uri, null);
+			this.headers = HttpHeaders.readOnlyHttpHeaders(headers);
+			this.cookies = unmodifiableCopy(cookies);
+			this.queryParams = parseQueryParams(uri);
+			this.body = body;
+		}
+
+		private static <K, V> MultiValueMap<K, V> unmodifiableCopy(MultiValueMap<K, V> original) {
+			return CollectionUtils.unmodifiableMultiValueMap(new LinkedMultiValueMap<>(original));
+		}
+
+		private static MultiValueMap<String, String> parseQueryParams(URI uri) {
+			MultiValueMap<String, String> queryParams = new LinkedMultiValueMap<>();
+			String query = uri.getRawQuery();
+			if (query != null) {
+				Matcher matcher = QUERY_PATTERN.matcher(query);
+				while (matcher.find()) {
+					String name = UriUtils.decode(matcher.group(1), StandardCharsets.UTF_8);
+					String eq = matcher.group(2);
+					String value = matcher.group(3);
+					if (value != null) {
+						value = UriUtils.decode(value, StandardCharsets.UTF_8);
+					}
+					else {
+						value = StringUtils.hasLength(eq) ? "" : null;
+					}
+					queryParams.add(name, value);
+				}
+			}
+			return queryParams;
+		}
+
+		@Nullable
+		@Override
+		public HttpMethod getMethod() {
+			return this.method;
+		}
+
+		@Override
+		public String getMethodValue() {
+			return this.method.name();
+		}
+
+		@Override
+		public URI getURI() {
+			return this.uri;
+		}
+
+		@Override
+		public RequestPath getPath() {
+			return this.path;
+		}
+
+		@Override
+		public HttpHeaders getHeaders() {
+			return this.headers;
+		}
+
+		@Override
+		public MultiValueMap<String, HttpCookie> getCookies() {
+			return this.cookies;
+		}
+
+		@Override
+		public MultiValueMap<String, String> getQueryParams() {
+			return this.queryParams;
+		}
+
+		@Override
+		public Flux<DataBuffer> getBody() {
+			return this.body;
+		}
+	}
+
+	private static class DelegatingServerWebExchange implements ServerWebExchange {
+
+		private static final ResolvableType FORM_DATA_TYPE =
+				ResolvableType.forClassWithGenerics(MultiValueMap.class, String.class, String.class);
+
+		private static final ResolvableType MULTIPART_DATA_TYPE = ResolvableType.forClassWithGenerics(
+				MultiValueMap.class, String.class, Part.class);
+
+		private static final Mono<MultiValueMap<String, String>> EMPTY_FORM_DATA =
+				Mono.just(CollectionUtils.unmodifiableMultiValueMap(new LinkedMultiValueMap<String, String>(0)))
+						.cache();
+
+		private static final Mono<MultiValueMap<String, Part>> EMPTY_MULTIPART_DATA =
+				Mono.just(CollectionUtils.unmodifiableMultiValueMap(new LinkedMultiValueMap<String, Part>(0)))
+						.cache();
+
+		private final ServerHttpRequest request;
+
+		private final ServerWebExchange delegate;
+
+		private final Mono<MultiValueMap<String, String>> formDataMono;
+
+		private final Mono<MultiValueMap<String, Part>> multipartDataMono;
+
+		public DelegatingServerWebExchange(ServerHttpRequest request, ServerWebExchange delegate,
+				List<HttpMessageReader<?>> messageReaders) {
+			this.request = request;
+			this.delegate = delegate;
+			this.formDataMono = initFormData(request, messageReaders);
+			this.multipartDataMono = initMultipartData(request, messageReaders);
+		}
+
+		@SuppressWarnings("unchecked")
+		private static Mono<MultiValueMap<String, String>> initFormData(ServerHttpRequest request,
+				List<HttpMessageReader<?>> readers) {
+
+			try {
+				MediaType contentType = request.getHeaders().getContentType();
+				if (MediaType.APPLICATION_FORM_URLENCODED.isCompatibleWith(contentType)) {
+					return ((HttpMessageReader<MultiValueMap<String, String>>) readers.stream()
+							.filter(reader -> reader.canRead(FORM_DATA_TYPE, MediaType.APPLICATION_FORM_URLENCODED))
+							.findFirst()
+							.orElseThrow(() -> new IllegalStateException("No form data HttpMessageReader.")))
+							.readMono(FORM_DATA_TYPE, request, Collections.emptyMap())
+							.switchIfEmpty(EMPTY_FORM_DATA)
+							.cache();
+				}
+			}
+			catch (InvalidMediaTypeException ex) {
+				// Ignore
+			}
+			return EMPTY_FORM_DATA;
+		}
+
+		@SuppressWarnings("unchecked")
+		private static Mono<MultiValueMap<String, Part>> initMultipartData(ServerHttpRequest request,
+				List<HttpMessageReader<?>> readers) {
+
+			try {
+				MediaType contentType = request.getHeaders().getContentType();
+				if (MediaType.MULTIPART_FORM_DATA.isCompatibleWith(contentType)) {
+					return ((HttpMessageReader<MultiValueMap<String, Part>>) readers.stream()
+							.filter(reader -> reader.canRead(MULTIPART_DATA_TYPE, MediaType.MULTIPART_FORM_DATA))
+							.findFirst()
+							.orElseThrow(() -> new IllegalStateException("No multipart HttpMessageReader.")))
+							.readMono(MULTIPART_DATA_TYPE, request, Collections.emptyMap())
+							.switchIfEmpty(EMPTY_MULTIPART_DATA)
+							.cache();
+				}
+			}
+			catch (InvalidMediaTypeException ex) {
+				// Ignore
+			}
+			return EMPTY_MULTIPART_DATA;
+		}
+		@Override
+		public ServerHttpRequest getRequest() {
+			return this.request;
+		}
+
+		@Override
+		public Mono<MultiValueMap<String, String>> getFormData() {
+			return this.formDataMono;
+		}
+
+		@Override
+		public Mono<MultiValueMap<String, Part>> getMultipartData() {
+			return this.multipartDataMono;
+		}
+
+		// Delegating methods
+
+		@Override
+		public ServerHttpResponse getResponse() {
+			return this.delegate.getResponse();
+		}
+
+		@Override
+		public Map<String, Object> getAttributes() {
+			return this.delegate.getAttributes();
+		}
+
+		@Override
+		public Mono<WebSession> getSession() {
+			return this.delegate.getSession();
+		}
+
+		@Override
+		public <T extends Principal> Mono<T> getPrincipal() {
+			return this.delegate.getPrincipal();
+		}
+
+
+		@Override
+		public LocaleContext getLocaleContext() {
+			return this.delegate.getLocaleContext();
+		}
+
+		@Nullable
+		@Override
+		public ApplicationContext getApplicationContext() {
+			return this.delegate.getApplicationContext();
+		}
+
+		@Override
+		public boolean isNotModified() {
+			return this.delegate.isNotModified();
+		}
+
+		@Override
+		public boolean checkNotModified(Instant lastModified) {
+			return this.delegate.checkNotModified(lastModified);
+		}
+
+		@Override
+		public boolean checkNotModified(String etag) {
+			return this.delegate.checkNotModified(etag);
+		}
+
+		@Override
+		public boolean checkNotModified(@Nullable String etag, Instant lastModified) {
+			return this.delegate.checkNotModified(etag, lastModified);
+		}
+
+		@Override
+		public String transformUrl(String url) {
+			return this.delegate.transformUrl(url);
+		}
+
+		@Override
+		public void addUrlTransformer(Function<String, String> transformer) {
+			this.delegate.addUrlTransformer(transformer);
+		}
+	}
+}

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

@@ -40,6 +40,7 @@ import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.http.HttpCookie;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.MediaType;
+import org.springframework.http.codec.HttpMessageReader;
 import org.springframework.http.codec.multipart.Part;
 import org.springframework.http.server.PathContainer;
 import org.springframework.http.server.reactive.ServerHttpRequest;
@@ -47,6 +48,7 @@ import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.reactive.function.BodyExtractor;
+import org.springframework.web.server.ServerWebExchange;
 import org.springframework.web.server.WebSession;
 import org.springframework.web.util.UriBuilder;
 import org.springframework.web.util.UriUtils;
@@ -524,6 +526,11 @@ public abstract class RequestPredicates {
 			return this.request.remoteAddress();
 		}
 
+		@Override
+		public List<HttpMessageReader<?>> messageReaders() {
+			return this.request.messageReaders();
+		}
+
 		@Override
 		public <T> T body(BodyExtractor<T, ? super ServerHttpRequest> extractor) {
 			return this.request.body(extractor);
@@ -604,6 +611,11 @@ public abstract class RequestPredicates {
 			return this.request.multipartData();
 		}
 
+		@Override
+		public ServerWebExchange exchange() {
+			return this.request.exchange();
+		}
+
 		@Override
 		public String toString() {
 			return method() + " " +  path();

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

@@ -25,11 +25,13 @@ import java.util.Locale;
 import java.util.Map;
 import java.util.Optional;
 import java.util.OptionalLong;
+import java.util.function.Consumer;
 
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.ParameterizedTypeReference;
+import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.http.HttpCookie;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
@@ -41,6 +43,7 @@ import org.springframework.http.codec.multipart.Part;
 import org.springframework.http.server.PathContainer;
 import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.reactive.function.BodyExtractor;
@@ -120,6 +123,11 @@ public interface ServerRequest {
 	 */
 	Optional<InetSocketAddress> remoteAddress();
 
+	/**
+	 * Return the readers used to convert the body of this request.
+	 */
+	List<HttpMessageReader<?>> messageReaders();
+
 	/**
 	 * Extract the body with the given {@code BodyExtractor}.
 	 * @param extractor the {@code BodyExtractor} that reads from the request
@@ -271,7 +279,16 @@ public interface ServerRequest {
 	 */
 	Mono<MultiValueMap<String, Part>> multipartData();
 
+	/**
+	 * Returns the web exchange that this request is based on. Manipulating the exchange directly,
+	 * instead of using the methods provided on {@code ServerRequest} and {@code ServerResponse},
+	 * can lead to irregular results.
+	 *
+	 * @return the web exchange
+	 */
+	ServerWebExchange exchange();
 
+	// Static methods
 
 	/**
 	 * Create a new {@code ServerRequest} based on the given {@code ServerWebExchange} and
@@ -284,6 +301,15 @@ public interface ServerRequest {
 		return new DefaultServerRequest(exchange, messageReaders);
 	}
 
+	/**
+	 * Create a builder with the status, headers, and cookies of the given request.
+	 * @param other the response to copy the status, headers, and cookies from
+	 * @return the created builder
+	 */
+	static Builder from(ServerRequest other) {
+		Assert.notNull(other, "'other' must not be null");
+		return new DefaultServerRequestBuilder(other);
+	}
 
 	/**
 	 * Represents the headers of the HTTP request.
@@ -349,4 +375,108 @@ public interface ServerRequest {
 		HttpHeaders asHttpHeaders();
 	}
 
+
+	/**
+	 * Defines a builder for a request.
+	 */
+	interface Builder {
+
+		/**
+		 * Set the method of the request.
+		 * @param method the new method
+		 * @return this builder
+		 */
+		Builder method(HttpMethod method);
+
+		/**
+		 * Set the uri of the request.
+		 * @param uri the new uri
+		 * @return this builder
+		 */
+		Builder uri(URI uri);
+
+		/**
+		 * Add the given header value(s) under the given name.
+		 * @param headerName  the header name
+		 * @param headerValues the header value(s)
+		 * @return this builder
+		 * @see HttpHeaders#add(String, String)
+		 */
+		Builder header(String headerName, String... headerValues);
+
+		/**
+		 * Manipulate this request's headers with the given consumer. The
+		 * headers provided to the consumer are "live", so that the consumer can be used to
+		 * {@linkplain HttpHeaders#set(String, String) overwrite} existing header values,
+		 * {@linkplain HttpHeaders#remove(Object) remove} values, or use any of the other
+		 * {@link HttpHeaders} methods.
+		 * @param headersConsumer a function that consumes the {@code HttpHeaders}
+		 * @return this builder
+		 */
+		Builder headers(Consumer<HttpHeaders> headersConsumer);
+
+		/**
+		 * Add a cookie with the given name and value(s).
+		 * @param name the cookie name
+		 * @param values the cookie value(s)
+		 * @return this builder
+		 */
+		Builder cookie(String name, String... values);
+
+		/**
+		 * Manipulate this request's cookies with the given consumer. The
+		 * map provided to the consumer is "live", so that the consumer can be used to
+		 * {@linkplain MultiValueMap#set(Object, Object) overwrite} existing header values,
+		 * {@linkplain MultiValueMap#remove(Object) remove} values, or use any of the other
+		 * {@link MultiValueMap} methods.
+		 * @param cookiesConsumer a function that consumes the cookies map
+		 * @return this builder
+		 */
+		Builder cookies(Consumer<MultiValueMap<String, HttpCookie>> cookiesConsumer);
+
+		/**
+		 * Sets the body of the request. Calling this methods will
+		 * {@linkplain org.springframework.core.io.buffer.DataBufferUtils#release(DataBuffer) release}
+		 * the existing body of the builder.
+		 * @param body the new body.
+		 * @return this builder
+		 */
+		Builder body(Flux<DataBuffer> body);
+
+		/**
+		 * Sets the body of the request to the UTF-8 encoded bytes of the given string.
+		 * Calling this methods will
+		 * {@linkplain org.springframework.core.io.buffer.DataBufferUtils#release(DataBuffer) release}
+		 * the existing body of the builder.
+		 * @param body the new body.
+		 * @return this builder
+		 */
+		Builder body(String body);
+
+		/**
+		 * Adds an attribute with the given name and value.
+		 * @param name  the attribute name
+		 * @param value the attribute value
+		 * @return this builder
+		 */
+		Builder attribute(String name, Object value);
+
+		/**
+		 * Manipulate this request's attributes with the given consumer. The map provided to the
+		 * consumer is "live", so that the consumer can be used to
+		 * {@linkplain Map#put(Object, Object) overwrite} existing header values,
+		 * {@linkplain Map#remove(Object) remove} values, or use any of the other
+		 * {@link Map} methods.
+		 * @param attributesConsumer a function that consumes the attributes map
+		 * @return this builder
+		 */
+		Builder attributes(Consumer<Map<String, Object>> attributesConsumer);
+
+		/**
+		 * Builds the request.
+		 * @return the built request
+		 */
+		ServerRequest build();
+	}
+
 }

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

@@ -35,6 +35,7 @@ import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpRange;
 import org.springframework.http.MediaType;
+import org.springframework.http.codec.HttpMessageReader;
 import org.springframework.http.codec.multipart.Part;
 import org.springframework.http.server.PathContainer;
 import org.springframework.http.server.reactive.ServerHttpRequest;
@@ -42,6 +43,7 @@ import org.springframework.util.Assert;
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.reactive.function.BodyExtractor;
 import org.springframework.web.reactive.function.server.ServerRequest;
+import org.springframework.web.server.ServerWebExchange;
 import org.springframework.web.server.WebSession;
 import org.springframework.web.util.UriBuilder;
 
@@ -121,6 +123,11 @@ public class ServerRequestWrapper implements ServerRequest {
 		return this.delegate.remoteAddress();
 	}
 
+	@Override
+	public List<HttpMessageReader<?>> messageReaders() {
+		return this.delegate.messageReaders();
+	}
+
 	@Override
 	public <T> T body(BodyExtractor<T, ? super ServerHttpRequest> extractor) {
 		return this.delegate.body(extractor);
@@ -201,6 +208,10 @@ public class ServerRequestWrapper implements ServerRequest {
 		return this.delegate.multipartData();
 	}
 
+	@Override
+	public ServerWebExchange exchange() {
+		return this.delegate.exchange();
+	}
 
 	/**
 	 * Implementation of the {@code Headers} interface that can be subclassed

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

+/*
+ * Copyright 2002-2018 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web.reactive.function.server;
+
+import java.nio.charset.StandardCharsets;
+
+import org.junit.Before;
+import org.junit.Test;
+import reactor.core.publisher.Flux;
+import reactor.test.StepVerifier;
+
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.core.io.buffer.DataBufferFactory;
+import org.springframework.core.io.buffer.DefaultDataBufferFactory;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.ResponseCookie;
+import org.springframework.mock.http.server.reactive.test.MockServerHttpRequest;
+import org.springframework.mock.web.test.server.MockServerWebExchange;
+
+import static org.junit.Assert.*;
+
+/**
+ * @author Arjen Poutsma
+ */
+public class DefaultServerRequestBuilderTests {
+
+	private DataBufferFactory dataBufferFactory;
+
+	@Before
+	public void createBufferFactory() {
+		this.dataBufferFactory = new DefaultDataBufferFactory();
+	}
+
+	@Test
+	public void from() throws Exception {
+
+		MockServerHttpRequest request = MockServerHttpRequest.post("http://example.com")
+				.header("foo", "bar")
+				.build();
+		MockServerWebExchange exchange = MockServerWebExchange.from(request);
+
+		ServerRequest other =
+				ServerRequest.create(exchange, HandlerStrategies.withDefaults().messageReaders());
+
+		Flux<DataBuffer> body = Flux.just("baz")
+				.map(s -> s.getBytes(StandardCharsets.UTF_8))
+				.map(dataBufferFactory::wrap);
+
+		ServerRequest result = ServerRequest.from(other)
+				.method(HttpMethod.HEAD)
+				.headers(httpHeaders -> httpHeaders.set("foo", "baar"))
+				.cookies(cookies -> cookies.set("baz", ResponseCookie.from("baz", "quux").build()))
+				.body(body)
+				.build();
+
+		assertEquals(HttpMethod.HEAD, result.method());
+		assertEquals(1, result.headers().asHttpHeaders().size());
+		assertEquals("baar", result.headers().asHttpHeaders().getFirst("foo"));
+		assertEquals(1, result.cookies().size());
+		assertEquals("quux", result.cookies().getFirst("baz").getValue());
+
+		StepVerifier.create(result.bodyToFlux(String.class))
+				.expectNext("baz")
+				.verifyComplete();
+	}
+
+}
\ No newline at end of file

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

@@ -40,6 +40,7 @@ import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpRange;
 import org.springframework.http.HttpRequest;
 import org.springframework.http.MediaType;
+import org.springframework.http.codec.HttpMessageReader;
 import org.springframework.http.codec.multipart.Part;
 import org.springframework.http.server.PathContainer;
 import org.springframework.http.server.RequestPath;
@@ -50,6 +51,7 @@ import org.springframework.util.CollectionUtils;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.reactive.function.BodyExtractor;
+import org.springframework.web.server.ServerWebExchange;
 import org.springframework.web.server.WebSession;
 import org.springframework.web.util.UriBuilder;
 import org.springframework.web.util.UriComponentsBuilder;
@@ -90,12 +92,18 @@ public class MockServerRequest implements ServerRequest {
 	@Nullable
 	private final InetSocketAddress remoteAddress;
 
+	private final List<HttpMessageReader<?>> messageReaders;
+
+	@Nullable
+	private final ServerWebExchange exchange;
+
 
 	private MockServerRequest(HttpMethod method, URI uri, String contextPath, MockHeaders headers,
 			MultiValueMap<String, HttpCookie> cookies, @Nullable Object body,
 			Map<String, Object> attributes, MultiValueMap<String, String> queryParams,
 			Map<String, String> pathVariables, @Nullable WebSession session, @Nullable Principal principal,
-			@Nullable InetSocketAddress remoteAddress) {
+			@Nullable InetSocketAddress remoteAddress, List<HttpMessageReader<?>> messageReaders,
+			@Nullable ServerWebExchange exchange) {
 
 		this.method = method;
 		this.uri = uri;
@@ -109,6 +117,8 @@ public class MockServerRequest implements ServerRequest {
 		this.session = session;
 		this.principal = principal;
 		this.remoteAddress = remoteAddress;
+		this.messageReaders = messageReaders;
+		this.exchange = exchange;
 	}
 
 
@@ -152,6 +162,11 @@ public class MockServerRequest implements ServerRequest {
 		return Optional.ofNullable(this.remoteAddress);
 	}
 
+	@Override
+	public List<HttpMessageReader<?>> messageReaders() {
+		return this.messageReaders;
+	}
+
 	@Override
 	@SuppressWarnings("unchecked")
 	public <S> S body(BodyExtractor<S, ? super ServerHttpRequest> extractor) {
@@ -233,6 +248,12 @@ public class MockServerRequest implements ServerRequest {
 		return (Mono<MultiValueMap<String, Part>>) this.body;
 	}
 
+	@Override
+	public ServerWebExchange exchange() {
+		Assert.state(this.exchange != null, "No exchange");
+		return this.exchange;
+	}
+
 	public static Builder builder() {
 		return new BuilderImpl();
 	}
@@ -271,7 +292,7 @@ public class MockServerRequest implements ServerRequest {
 		Builder session(WebSession session);
 
 		/**
-		 * @deprecated  in favor of {@link #principal(Principal)}
+		 * @deprecated in favor of {@link #principal(Principal)}
 		 */
 		@Deprecated
 		Builder session(Principal principal);
@@ -280,6 +301,10 @@ public class MockServerRequest implements ServerRequest {
 
 		Builder remoteAddress(InetSocketAddress remoteAddress);
 
+		Builder messageReaders(List<HttpMessageReader<?>> messageReaders);
+
+		Builder exchange(ServerWebExchange exchange);
+
 		MockServerRequest body(Object body);
 
 		MockServerRequest build();
@@ -316,6 +341,11 @@ public class MockServerRequest implements ServerRequest {
 		@Nullable
 		private InetSocketAddress remoteAddress;
 
+		private List<HttpMessageReader<?>> messageReaders = HandlerStrategies.withDefaults().messageReaders();
+
+		@Nullable
+		private ServerWebExchange exchange;
+
 		@Override
 		public Builder method(HttpMethod method) {
 			Assert.notNull(method, "'method' must not be null");
@@ -419,6 +449,7 @@ public class MockServerRequest implements ServerRequest {
 		}
 
 		@Override
+		@Deprecated
 		public Builder session(Principal principal) {
 			return principal(principal);
 		}
@@ -437,19 +468,35 @@ public class MockServerRequest implements ServerRequest {
 			return this;
 		}
 
+		@Override
+		public Builder messageReaders(List<HttpMessageReader<?>> messageReaders) {
+			Assert.notNull(messageReaders, "'messageReaders' must not be null");
+			this.messageReaders = messageReaders;
+			return this;
+		}
+
+		@Override
+		public Builder exchange(ServerWebExchange exchange) {
+			Assert.notNull(exchange, "'exchange' must not be null");
+			this.exchange = exchange;
+			return this;
+		}
+
 		@Override
 		public MockServerRequest body(Object body) {
 			this.body = body;
 			return new MockServerRequest(this.method, this.uri, this.contextPath, this.headers,
 					this.cookies, this.body, this.attributes, this.queryParams, this.pathVariables,
-					this.session, this.principal, this.remoteAddress);
+					this.session, this.principal, this.remoteAddress, this.messageReaders,
+					this.exchange);
 		}
 
 		@Override
 		public MockServerRequest build() {
 			return new MockServerRequest(this.method, this.uri, this.contextPath, this.headers,
 					this.cookies, null, this.attributes, this.queryParams, this.pathVariables,
-					this.session, this.principal, this.remoteAddress);
+					this.session, this.principal, this.remoteAddress, this.messageReaders,
+					this.exchange);
 		}
 	}