Add resource redirection to WebMVC functional router

See gh-27257

spring-webmvc/src/main/java/org/springframework/web/servlet/function/PredicateResourceLookupFunction.java

@@ -0,0 +1,50 @@
+/*
+ * 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.servlet.function;
+
+import java.util.Optional;
+import java.util.function.Function;
+
+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, Optional<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 Optional<Resource> apply(ServerRequest serverRequest) {
+		return this.predicate.test(serverRequest) ? Optional.of(this.resource) : Optional.empty();
+	}
+
+}

spring-webmvc/src/main/java/org/springframework/web/servlet/function/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.
@@ -37,6 +37,7 @@ import org.springframework.util.Assert;
  * Default implementation of {@link RouterFunctions.Builder}.
  *
  * @author Arjen Poutsma
+ * @author Sebastien Deleuze
  * @since 5.2
  */
 class RouterFunctionBuilder implements RouterFunctions.Builder {
@@ -236,6 +237,17 @@ 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-webmvc/src/main/java/org/springframework/web/servlet/function/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.
@@ -45,6 +45,7 @@ import org.springframework.web.util.pattern.PathPatternParser;
  * function.
  *
  * @author Arjen Poutsma
+ * @author Sebastien Deleuze
  * @since 5.2
  */
 public abstract class RouterFunctions {
@@ -128,6 +129,40 @@ 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
@@ -602,6 +637,35 @@ 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-webmvc/src/main/kotlin/org/springframework/web/servlet/function/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.
@@ -612,6 +612,15 @@ class RouterFunctionDsl internal constructor (private val init: (RouterFunctionD
 		builder.add(RouterFunctions.route(RequestPredicates.path(this), HandlerFunction(f)))
 	}
 
+	/**
+	 * Route requests that match the given predicate to the given resource.
+	 * @see RouterFunctions.resource
+	 * @since 6.1.4
+	 */
+	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-webmvc/src/test/java/org/springframework/web/servlet/function/RouterFunctionBuilderTests.java

@@ -39,11 +39,13 @@ import org.springframework.web.testfixture.servlet.MockHttpServletRequest;
 import static java.util.Collections.emptyList;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.springframework.web.servlet.function.RequestPredicates.HEAD;
+import static org.springframework.web.servlet.function.RequestPredicates.path;
 
 /**
  * Tests for {@link RouterFunctionBuilder}.
  *
  * @author Arjen Poutsma
+ * @author Sebastien Deleuze
  */
 class RouterFunctionBuilderTests {
 
@@ -96,6 +98,23 @@ class RouterFunctionBuilderTests {
 		}
 	}
 
+	@Test
+	void resource() {
+		Resource resource = new ClassPathResource("/org/springframework/web/servlet/function/response.txt");
+		assertThat(resource.exists()).isTrue();
+
+		RouterFunction<ServerResponse> route = RouterFunctions.route()
+				.resource(path("/test"), resource)
+				.build();
+
+		ServerRequest resourceRequest = initRequest("GET", "/test");
+
+		Optional<HttpStatusCode> responseStatus = route.route(resourceRequest)
+				.map(handlerFunction -> handle(handlerFunction, resourceRequest))
+				.map(ServerResponse::statusCode);
+		assertThat(responseStatus).contains(HttpStatus.OK);
+	}
+
 	@Test
 	void resources() {
 		Resource resource = new ClassPathResource("/org/springframework/web/servlet/function/");

spring-webmvc/src/test/kotlin/org/springframework/web/servlet/function/RouterFunctionDslTests.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 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.
@@ -74,14 +74,6 @@ class RouterFunctionDslTests {
 		assertThat(sampleRouter().route(request).isPresent).isTrue()
 	}
 
-	@Test
-	fun resourceByPath() {
-		val servletRequest = PathPatternsTestUtils.initRequest(
-				"GET", "/org/springframework/web/servlet/function/response.txt", true)
-		val request = DefaultServerRequest(servletRequest, emptyList())
-		assertThat(sampleRouter().route(request).isPresent).isTrue()
-	}
-
 	@Test
 	fun method() {
 		val servletRequest = PathPatternsTestUtils.initRequest("PATCH", "/", true)
@@ -98,6 +90,20 @@ class RouterFunctionDslTests {
 
 	@Test
 	fun resource() {
+		val servletRequest = PathPatternsTestUtils.initRequest("GET","/response2.txt", true)
+		val request = DefaultServerRequest(servletRequest, emptyList())
+		assertThat(sampleRouter().route(request).isPresent).isTrue()
+	}
+
+	@Test
+	fun resources() {
+		val servletRequest = PathPatternsTestUtils.initRequest("GET", "/resources/response.txt", true)
+		val request = DefaultServerRequest(servletRequest, emptyList())
+		assertThat(sampleRouter().route(request).isPresent).isTrue()
+	}
+
+	@Test
+	fun resourcesLookupFunction() {
 		val servletRequest = PathPatternsTestUtils.initRequest("GET", "/response.txt", true)
 		val request = DefaultServerRequest(servletRequest, emptyList())
 		assertThat(sampleRouter().route(request).isPresent).isTrue()
@@ -168,8 +174,9 @@ class RouterFunctionDslTests {
 			GET("/api/foo/", ::handle)
 		}
 		headers({ it.header("bar").isNotEmpty() }, ::handle)
-		resources("/org/springframework/web/servlet/function/**",
+		resource(path("/response2.txt"), ClassPathResource("/org/springframework/web/servlet/function/response.txt"))
-				ClassPathResource("/org/springframework/web/servlet/function/response.txt"))
+		resources("/resources/**",
+			ClassPathResource("/org/springframework/web/servlet/function/"))
 		resources {
 			if (it.path() == "/response.txt") {
 				ClassPathResource("/org/springframework/web/servlet/function/response.txt")