#983 - Switch to Spring's ServerWebExchangeContextFilter.

Replace HypermediaWebFilter with ServerWebExchangeContextFilter.

Related issues: #986, spring-projects/spring-framework#21746.

src/main/java/org/springframework/hateoas/config/WebFluxHateoasConfiguration.java

@@ -27,13 +27,13 @@ import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Lazy;
 import org.springframework.core.codec.CharSequenceEncoder;
 import org.springframework.core.codec.StringDecoder;
-import org.springframework.hateoas.server.reactive.HypermediaWebFilter;
 import org.springframework.http.codec.CodecConfigurer;
 import org.springframework.http.codec.ServerCodecConfigurer;
 import org.springframework.http.codec.json.Jackson2JsonDecoder;
 import org.springframework.http.codec.json.Jackson2JsonEncoder;
 import org.springframework.lang.NonNull;
 import org.springframework.util.MimeType;
+import org.springframework.web.filter.reactive.ServerWebExchangeContextFilter;
 import org.springframework.web.reactive.config.WebFluxConfigurer;
 import org.springframework.web.reactive.function.client.WebClient;
 
@@ -67,14 +67,10 @@ class WebFluxHateoasConfiguration {
 		return new HypermediaWebFluxConfigurer(mapper.getIfAvailable(ObjectMapper::new), hypermediaTypes);
 	}
 
-	/**
-	 * TODO: Replace with Spring Framework filter when https://github.com/spring-projects/spring-framework/issues/21746 is
-	 * completed.
-	 */
 	@Bean
-	@Lazy // To avoid creation on a WebMVC app using WebClient only
-	HypermediaWebFilter hypermediaWebFilter() {
-		return new HypermediaWebFilter();
+	@Lazy
+	ServerWebExchangeContextFilter serverWebExchangeContextFilter() {
+		return new ServerWebExchangeContextFilter();
 	}
 
 	/**

src/main/java/org/springframework/hateoas/server/reactive/HypermediaWebFilter.java

@@ -1,44 +0,0 @@
-/*
- * Copyright 2019 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      https://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.hateoas.server.reactive;
-
-import reactor.core.publisher.Mono;
-import reactor.util.context.Context;
-
-import org.springframework.web.server.ServerWebExchange;
-import org.springframework.web.server.WebFilter;
-import org.springframework.web.server.WebFilterChain;
-
-/**
- * {@link WebFilter} that ensures a copy of the {@link ServerWebExchange} is added to the Reactor {@link Context}.
- *
- * @author Greg Turnquist
- * @since 1.0
- */
-public class HypermediaWebFilter implements WebFilter {
-
-	public static final String SERVER_WEB_EXCHANGE = "serverWebExchange";
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.web.server.WebFilter#filter(org.springframework.web.server.ServerWebExchange, org.springframework.web.server.WebFilterChain)
-	 */
-	@Override
-	public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {
-		return chain.filter(exchange) //
-				.subscriberContext(Context.of(SERVER_WEB_EXCHANGE, exchange));
-	}
-}

src/main/java/org/springframework/hateoas/server/reactive/WebFluxLinkBuilder.java

@@ -15,7 +15,7 @@
  */
 package org.springframework.hateoas.server.reactive;
 
-import static org.springframework.hateoas.server.reactive.HypermediaWebFilter.*;
+import static org.springframework.web.filter.reactive.ServerWebExchangeContextFilter.*;
 
 import lombok.RequiredArgsConstructor;
 
@@ -241,7 +241,7 @@ public class WebFluxLinkBuilder extends TemplateVariableAwareLinkBuilderSupport<
 	private static Mono<WebFluxLinkBuilder> linkToInternal(Object invocation) {
 
 		return linkToInternal(invocation,
-				Mono.subscriberContext().map(context -> getBuilder(context.getOrDefault(SERVER_WEB_EXCHANGE, null))));
+				Mono.subscriberContext().map(context -> getBuilder(context.getOrDefault(EXCHANGE_CONTEXT_ATTRIBUTE, null))));
 	}
 
 	private static Mono<WebFluxLinkBuilder> linkToInternal(Object invocation, Mono<UriComponentsBuilder> exchange) {

src/test/java/org/springframework/hateoas/server/reactive/HypermediaWebFilterTest.java

@@ -40,6 +40,8 @@ import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.reactive.config.EnableWebFlux;
 
 /**
+ * Verify WebFlux properly activates the {@link org.springframework.web.filter.reactive.ServerWebExchangeContextFilter}.
+ *
  * @author Greg Turnquist
  */
 class HypermediaWebFilterTest {

src/test/java/org/springframework/hateoas/server/reactive/WebFluxLinkBuilderTest.java

@@ -17,8 +17,8 @@ package org.springframework.hateoas.server.reactive;
 
 import static org.assertj.core.api.Assertions.*;
 import static org.mockito.Mockito.*;
-import static org.springframework.hateoas.server.reactive.HypermediaWebFilter.*;
 import static org.springframework.hateoas.server.reactive.WebFluxLinkBuilder.*;
+import static org.springframework.web.filter.reactive.ServerWebExchangeContextFilter.*;
 
 import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
@@ -82,7 +82,7 @@ class WebFluxLinkBuilderTest {
 		when(this.request.getHeaders()).thenReturn(new HttpHeaders());
 
 		linkTo(methodOn(TestController.class).root()).withSelfRel().toMono() //
-				.subscriberContext(Context.of(SERVER_WEB_EXCHANGE, this.exchange)) //
+				.subscriberContext(Context.of(EXCHANGE_CONTEXT_ATTRIBUTE, this.exchange)) //
 				.as(StepVerifier::create).expectNextMatches(link -> {
 
 					assertThat(link.getRel()).isEqualTo(IanaLinkRelations.SELF);
@@ -126,7 +126,7 @@ class WebFluxLinkBuilderTest {
 		when(this.request.getHeaders()).thenReturn(new HttpHeaders());
 
 		linkTo(methodOn(TestController.class).root()).withSelfRel().toMono() //
-				.subscriberContext(Context.of(SERVER_WEB_EXCHANGE, this.exchange)) //
+				.subscriberContext(Context.of(EXCHANGE_CONTEXT_ATTRIBUTE, this.exchange)) //
 				.as(StepVerifier::create).expectNextMatches(link -> {
 
 					assertThat(link.getRel()).isEqualTo(IanaLinkRelations.SELF);
@@ -169,7 +169,7 @@ class WebFluxLinkBuilderTest {
 		when(this.request.getHeaders()).thenReturn(new HttpHeaders());
 
 		linkTo(methodOn(TestController.class).deep()).withSelfRel().toMono() //
-				.subscriberContext(Context.of(SERVER_WEB_EXCHANGE, this.exchange)) //
+				.subscriberContext(Context.of(EXCHANGE_CONTEXT_ATTRIBUTE, this.exchange)) //
 				.as(StepVerifier::create).expectNextMatches(link -> {
 
 					assertThat(link.getRel()).isEqualTo(IanaLinkRelations.SELF);
@@ -191,7 +191,7 @@ class WebFluxLinkBuilderTest {
 		when(this.request.getHeaders()).thenReturn(new HttpHeaders());
 
 		linkTo(methodOn(TestController2.class).root()).withSelfRel().toMono() //
-				.subscriberContext(Context.of(SERVER_WEB_EXCHANGE, this.exchange)) //
+				.subscriberContext(Context.of(EXCHANGE_CONTEXT_ATTRIBUTE, this.exchange)) //
 				.as(StepVerifier::create).expectNextMatches(link -> {
 
 					assertThat(link.getRel()).isEqualTo(IanaLinkRelations.SELF);