Add resource redirection to WebFlux functional router

See gh-27257

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

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2002-2024 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.web.reactive.function.server;
+
+import java.util.function.Function;
+
+import reactor.core.publisher.Mono;
+
+import org.springframework.core.io.Resource;
+import org.springframework.util.Assert;
+
+/**
+ * Lookup function used by {@link RouterFunctions#resource(RequestPredicate, Resource)} and
+ * {@link RouterFunctions#resource(RequestPredicate, Resource, java.util.function.BiConsumer)}.
+ *
+ * @author Sebastien Deleuze
+ * @since 6.1.4
+ */
+class PredicateResourceLookupFunction implements Function<ServerRequest, Mono<Resource>> {
+
+	private final RequestPredicate predicate;
+
+	private final Resource resource;
+
+	public PredicateResourceLookupFunction(RequestPredicate predicate, Resource resource) {
+		Assert.notNull(predicate, "'predicate' must not be null");
+		Assert.notNull(resource, "'resource' must not be null");
+		this.predicate = predicate;
+		this.resource = resource;
+	}
+
+	@Override
+	public Mono<Resource> apply(ServerRequest serverRequest) {
+		return this.predicate.test(serverRequest) ? Mono.just(this.resource) : Mono.empty();
+	}
+
+}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -39,6 +39,7 @@ import org.springframework.util.Assert;
  * Default implementation of {@link RouterFunctions.Builder}.
  *
  * @author Arjen Poutsma
+ * @author Sebastien Deleuze
  * @since 5.1
  */
 class RouterFunctionBuilder implements RouterFunctions.Builder {
@@ -238,6 +239,17 @@ class RouterFunctionBuilder implements RouterFunctions.Builder {
 		return add(RouterFunctions.route(predicate, handlerFunction));
 	}
 
+	@Override
+	public RouterFunctions.Builder resource(RequestPredicate predicate, Resource resource) {
+		return add(RouterFunctions.resource(predicate, resource));
+	}
+
+	@Override
+	public RouterFunctions.Builder resource(RequestPredicate predicate, Resource resource,
+			BiConsumer<Resource, HttpHeaders> headersConsumer) {
+		return add(RouterFunctions.resource(predicate, resource, headersConsumer));
+	}
+
 	@Override
 	public RouterFunctions.Builder resources(String pattern, Resource location) {
 		return add(RouterFunctions.resources(pattern, location));

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -59,6 +59,7 @@ import org.springframework.web.util.pattern.PathPatternParser;
  * environments, Reactor, or Undertow.
  *
  * @author Arjen Poutsma
+ * @author Sebastien Deleuze
  * @since 5.0
  */
 public abstract class RouterFunctions {
@@ -145,6 +146,40 @@ public abstract class RouterFunctions {
 		return new DefaultNestedRouterFunction<>(predicate, routerFunction);
 	}
 
+	/**
+	 * Route requests that match the given predicate to the given resource.
+	 * For instance
+	 * <pre class="code">
+	 * Resource resource = new ClassPathResource("static/index.html")
+	 * RouterFunction&lt;ServerResponse&gt; resources = RouterFunctions.resource(path("/api/**").negate(), resource);
+	 * </pre>
+	 * @param predicate predicate to match
+	 * @param resource the resources to serve
+	 * @return a router function that routes to a resource
+	 * @since 6.1.4
+	 */
+	public static RouterFunction<ServerResponse> resource(RequestPredicate predicate, Resource resource) {
+		return resources(new PredicateResourceLookupFunction(predicate, resource), (consumerResource, httpHeaders) -> {});
+	}
+
+	/**
+	 * Route requests that match the given predicate to the given resource.
+	 * For instance
+	 * <pre class="code">
+	 * Resource resource = new ClassPathResource("static/index.html")
+	 * RouterFunction&lt;ServerResponse&gt; resources = RouterFunctions.resource(path("/api/**").negate(), resource);
+	 * </pre>
+	 * @param predicate predicate to match
+	 * @param resource the resources to serve
+	 * @param headersConsumer provides access to the HTTP headers for served resources
+	 * @return a router function that routes to a resource
+	 * @since 6.1.4
+	 */
+	public static RouterFunction<ServerResponse> resource(RequestPredicate predicate, Resource resource,
+			BiConsumer<Resource, HttpHeaders> headersConsumer) {
+		return resources(new PredicateResourceLookupFunction(predicate, resource), headersConsumer);
+	}
+
 	/**
 	 * Route requests that match the given pattern to resources relative to the given root location.
 	 * For instance
@@ -692,6 +727,35 @@ public abstract class RouterFunctions {
 		 */
 		Builder add(RouterFunction<ServerResponse> routerFunction);
 
+		/**
+		 * Route requests that match the given predicate to the given resource.
+		 * For instance
+		 * <pre class="code">
+		 * Resource resource = new ClassPathResource("static/index.html")
+		 * RouterFunction&lt;ServerResponse&gt; resources = RouterFunctions.resource(path("/api/**").negate(), resource);
+		 * </pre>
+		 * @param predicate predicate to match
+		 * @param resource the resources to serve
+		 * @return a router function that routes to a resource
+		 * @since 6.1.4
+		 */
+		Builder resource(RequestPredicate predicate, Resource resource);
+
+		/**
+		 * Route requests that match the given predicate to the given resource.
+		 * For instance
+		 * <pre class="code">
+		 * Resource resource = new ClassPathResource("static/index.html")
+		 * RouterFunction&lt;ServerResponse&gt; resources = RouterFunctions.resource(path("/api/**").negate(), resource);
+		 * </pre>
+		 * @param predicate predicate to match
+		 * @param resource the resources to serve
+		 * @param headersConsumer provides access to the HTTP headers for served resources
+		 * @return a router function that routes to a resource
+		 * @since 6.1.4
+		 */
+		Builder resource(RequestPredicate predicate, Resource resource, BiConsumer<Resource, HttpHeaders> headersConsumer);
+
 		/**
 		 * Route requests that match the given pattern to resources relative to the given root location.
 		 * For instance

spring-webflux/src/main/kotlin/org/springframework/web/reactive/function/server/CoRouterFunctionDsl.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -23,6 +23,7 @@ import kotlinx.coroutines.reactor.awaitSingle
 import kotlinx.coroutines.reactor.mono
 import kotlinx.coroutines.withContext
 import org.springframework.core.io.Resource
+import org.springframework.http.HttpHeaders
 import org.springframework.http.HttpMethod
 import org.springframework.http.HttpStatusCode
 import org.springframework.http.MediaType
@@ -499,6 +500,15 @@ class CoRouterFunctionDsl internal constructor (private val init: (CoRouterFunct
 		builder.add(RouterFunctions.route(RequestPredicates.path(this),  asHandlerFunction(f)))
 	}
 
+	/**
+	 * Route requests that match the given predicate to the given resource.
+	 * @since 6.1.4
+	 * @see RouterFunctions.resource
+	 */
+	fun resource(predicate: RequestPredicate, resource: Resource, headersConsumer: (Resource, HttpHeaders) -> Unit = { _, _ -> }) {
+		builder.resource(predicate, resource, headersConsumer)
+	}
+
 	/**
 	 * Route requests that match the given pattern to resources relative to the given root location.
 	 * @see RouterFunctions.resources

spring-webflux/src/main/kotlin/org/springframework/web/reactive/function/server/RouterFunctionDsl.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -617,6 +617,15 @@ class RouterFunctionDsl internal constructor (private val init: RouterFunctionDs
 		builder.add(RouterFunctions.route(RequestPredicates.path(this),  HandlerFunction { f(it).cast(ServerResponse::class.java) }))
 	}
 
+	/**
+	 * Route requests that match the given predicate to the given resource.
+	 * @since 6.1.4
+	 * @see RouterFunctions.resource
+	 */
+	fun resource(predicate: RequestPredicate, resource: Resource) {
+		builder.resource(predicate, resource)
+	}
+
 	/**
 	 * Route requests that match the given pattern to resources relative to the given root location.
 	 * @see RouterFunctions.resources

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

@@ -39,6 +39,7 @@ import org.springframework.web.testfixture.server.MockServerWebExchange;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.springframework.web.reactive.function.server.RequestPredicates.HEAD;
+import static org.springframework.web.reactive.function.server.RequestPredicates.path;
 
 /**
  * @author Arjen Poutsma
@@ -102,6 +103,27 @@ class RouterFunctionBuilderTests {
 
 	}
 
+	@Test
+	void resource() {
+		Resource resource = new ClassPathResource("/org/springframework/web/reactive/function/server/response.txt");
+		assertThat(resource.exists()).isTrue();
+
+		RouterFunction<ServerResponse> route = RouterFunctions.route()
+				.resource(path("/test"), resource)
+				.build();
+
+		MockServerHttpRequest mockRequest = MockServerHttpRequest.get("https://localhost/test").build();
+		ServerRequest resourceRequest = new DefaultServerRequest(MockServerWebExchange.from(mockRequest), Collections.emptyList());
+
+		Mono<HttpStatusCode> responseMono = route.route(resourceRequest)
+				.flatMap(handlerFunction -> handlerFunction.handle(resourceRequest))
+				.map(ServerResponse::statusCode);
+
+		StepVerifier.create(responseMono)
+				.expectNext(HttpStatus.OK)
+				.verifyComplete();
+	}
+
 	@Test
 	void resources() {
 		Resource resource = new ClassPathResource("/org/springframework/web/reactive/function/server/");

spring-webflux/src/test/kotlin/org/springframework/web/reactive/function/server/CoRouterFunctionDslTests.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -93,16 +93,6 @@ class CoRouterFunctionDslTests {
 				.verifyComplete()
 	}
 
-	@Test
-	fun resourceByPath() {
-		val mockRequest = get("https://example.com/org/springframework/web/reactive/function/response.txt")
-				.build()
-		val request = DefaultServerRequest(MockServerWebExchange.from(mockRequest), emptyList())
-		StepVerifier.create(sampleRouter().route(request))
-				.expectNextCount(1)
-				.verifyComplete()
-	}
-
 	@Test
 	fun method() {
 		val mockRequest = patch("https://example.com/")
@@ -124,6 +114,24 @@ class CoRouterFunctionDslTests {
 
 	@Test
 	fun resource() {
+		val mockRequest = get("https://example.com/response2.txt").build()
+		val request = DefaultServerRequest(MockServerWebExchange.from(mockRequest), emptyList())
+		StepVerifier.create(sampleRouter().route(request))
+			.expectNextCount(1)
+			.verifyComplete()
+	}
+
+	@Test
+	fun resources() {
+		val mockRequest = get("https://example.com/resources/response.txt").build()
+		val request = DefaultServerRequest(MockServerWebExchange.from(mockRequest), emptyList())
+		StepVerifier.create(sampleRouter().route(request))
+			.expectNextCount(1)
+			.verifyComplete()
+	}
+
+	@Test
+	fun resourcesLookupFunction() {
 		val mockRequest = get("https://example.com/response.txt").build()
 		val request = DefaultServerRequest(MockServerWebExchange.from(mockRequest), emptyList())
 		StepVerifier.create(sampleRouter().route(request))
@@ -305,8 +313,9 @@ class CoRouterFunctionDslTests {
 			GET("/api/foo/", ::handle)
 		}
 		headers({ it.header("bar").isNotEmpty() }, ::handle)
-		resources("/org/springframework/web/reactive/function/**",
-				ClassPathResource("/org/springframework/web/reactive/function/response.txt"))
+		resource(path("/response2.txt"), ClassPathResource("/org/springframework/web/reactive/function/response.txt"))
+		resources("/resources/**",
+			ClassPathResource("/org/springframework/web/reactive/function/"))
 		resources {
 			if (it.path() == "/response.txt") {
 				ClassPathResource("/org/springframework/web/reactive/function/response.txt")

spring-webflux/src/test/kotlin/org/springframework/web/reactive/function/server/RouterFunctionDslTests.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -91,16 +91,6 @@ class RouterFunctionDslTests {
 				.verifyComplete()
 	}
 
-	@Test
-	fun resourceByPath() {
-		val mockRequest = get("https://example.com/org/springframework/web/reactive/function/response.txt")
-				.build()
-		val request = DefaultServerRequest(MockServerWebExchange.from(mockRequest), emptyList())
-		StepVerifier.create(sampleRouter().route(request))
-				.expectNextCount(1)
-				.verifyComplete()
-	}
-
 	@Test
 	fun method() {
 		val mockRequest = patch("https://example.com/")
@@ -122,6 +112,24 @@ class RouterFunctionDslTests {
 
 	@Test
 	fun resource() {
+		val mockRequest = get("https://example.com/response2.txt").build()
+		val request = DefaultServerRequest(MockServerWebExchange.from(mockRequest), emptyList())
+		StepVerifier.create(sampleRouter().route(request))
+			.expectNextCount(1)
+			.verifyComplete()
+	}
+
+	@Test
+	fun resources() {
+		val mockRequest = get("https://example.com/resources/response.txt").build()
+		val request = DefaultServerRequest(MockServerWebExchange.from(mockRequest), emptyList())
+		StepVerifier.create(sampleRouter().route(request))
+			.expectNextCount(1)
+			.verifyComplete()
+	}
+
+	@Test
+	fun resourcesLookupFunction() {
 		val mockRequest = get("https://example.com/response.txt").build()
 		val request = DefaultServerRequest(MockServerWebExchange.from(mockRequest), emptyList())
 		StepVerifier.create(sampleRouter().route(request))
@@ -237,8 +245,9 @@ class RouterFunctionDslTests {
 			GET("/api/foo/", ::handle)
 		}
 		headers({ it.header("bar").isNotEmpty() }, ::handle)
-		resources("/org/springframework/web/reactive/function/**",
-				ClassPathResource("/org/springframework/web/reactive/function/response.txt"))
+		resource(path("/response2.txt"), ClassPathResource("/org/springframework/web/reactive/function/response.txt"))
+		resources("/resources/**",
+				ClassPathResource("/org/springframework/web/reactive/function/"))
 		resources {
 			if (it.path() == "/response.txt") {
 				Mono.just(ClassPathResource("/org/springframework/web/reactive/function/response.txt"))