Support dynamic paths in route URI using SetRequestUri filter

docs/modules/ROOT/pages/spring-cloud-gateway-server-webflux/gatewayfilter-factories/seturi-factory.adoc

@@ -0,0 +1,26 @@
+[[seturi-gatewayfilter-factory]]
+= `SetRequestUri` `GatewayFilter` Factory
+
+The `SetRequestUri` `GatewayFilter` factory takes a `uri` parameter.
+It offers a simple way to manipulate the request uri by allowing templated segments of the path.
+This uses the URI templates from Spring Framework.
+Multiple matching segments are allowed.
+The following listing configures a `SetRequestUri` `GatewayFilter`:
+
+.application.yml
+[source,yaml]
+----
+spring:
+  cloud:
+    gateway:
+      routes:
+      - id: seturi_route
+        uri: no://op
+        predicates:
+        - Path=/{appId}/**
+        filters:
+        - SetRequestUri=http://{appId}.example.com
+----
+
+For a request path of `/red-application/blue`, this sets the uri to `http://red-application.example.com` before making the downstream request and the final url, including path is going to be `http://red-application.example.com/red-application/blue`
+

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/config/GatewayAutoConfiguration.java

@@ -110,6 +110,7 @@
 import org.springframework.cloud.gateway.filter.factory.SetPathGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SetRequestHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SetRequestHostHeaderGatewayFilterFactory;
+import org.springframework.cloud.gateway.filter.factory.SetRequestUriGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SetResponseHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SetStatusGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.StripPrefixGatewayFilterFactory;
@@ -718,6 +719,12 @@ public RequestHeaderToRequestUriGatewayFilterFactory requestHeaderToRequestUriGa
 		return new RequestHeaderToRequestUriGatewayFilterFactory();
 	}
 
+	@Bean
+	@ConditionalOnEnabledFilter
+	public SetRequestUriGatewayFilterFactory setRequestUriGatewayFilterFactory() {
+		return new SetRequestUriGatewayFilterFactory();
+	}
+
 	@Bean
 	@ConditionalOnEnabledFilter
 	public RequestSizeGatewayFilterFactory requestSizeGatewayFilterFactory() {

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/filter/factory/SetRequestUriGatewayFilterFactory.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright 2013-2020 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.cloud.gateway.filter.factory;
+
+import java.net.URI;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import org.springframework.cloud.gateway.filter.GatewayFilter;
+import org.springframework.cloud.gateway.filter.OrderedGatewayFilter;
+import org.springframework.web.server.ServerWebExchange;
+import org.springframework.web.util.UriComponentsBuilder;
+
+import static org.springframework.cloud.gateway.support.GatewayToStringStyler.filterToStringCreator;
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.getUriTemplateVariables;
+
+/**
+ * This filter changes the request uri.
+ *
+ * @author Stepan Mikhailiuk
+ */
+public class SetRequestUriGatewayFilterFactory
+		extends AbstractChangeRequestUriGatewayFilterFactory<SetRequestUriGatewayFilterFactory.Config> {
+
+	private static final Logger log = LoggerFactory.getLogger(SetRequestUriGatewayFilterFactory.class);
+
+	public SetRequestUriGatewayFilterFactory() {
+		super(Config.class);
+	}
+
+	@Override
+	public List<String> shortcutFieldOrder() {
+		return Arrays.asList(NAME_KEY);
+	}
+
+	@Override
+	public GatewayFilter apply(Config config) {
+		// AbstractChangeRequestUriGatewayFilterFactory.apply() returns
+		// OrderedGatewayFilter
+		OrderedGatewayFilter gatewayFilter = (OrderedGatewayFilter) super.apply(config);
+		return new OrderedGatewayFilter(gatewayFilter, gatewayFilter.getOrder()) {
+			@Override
+			public String toString() {
+				return filterToStringCreator(SetRequestUriGatewayFilterFactory.this)
+					.append("template", config.getTemplate())
+					.toString();
+			}
+		};
+	}
+
+	String getUri(ServerWebExchange exchange, Config config) {
+		String template = config.getTemplate();
+
+		if (template.indexOf('{') == -1) {
+			return template;
+		}
+
+		Map<String, String> variables = getUriTemplateVariables(exchange);
+		return UriComponentsBuilder.fromUriString(template).build().expand(variables).toUriString();
+	}
+
+	@Override
+	protected Optional<URI> determineRequestUri(ServerWebExchange exchange, Config config) {
+		try {
+			String url = getUri(exchange, config);
+			URI uri = URI.create(url);
+			if (!uri.isAbsolute()) {
+				throw new IllegalArgumentException("URI is not absolute");
+			}
+			return Optional.of(uri);
+		}
+		catch (IllegalArgumentException e) {
+
+			log.info("Request url is invalid : url={}, error={}", config.getTemplate(), e.getMessage());
+			return Optional.ofNullable(null);
+		}
+	}
+
+	public static class Config {
+
+		private String template;
+
+		public String getTemplate() {
+			return template;
+		}
+
+		public void setTemplate(String template) {
+			this.template = template;
+		}
+
+	}
+
+}

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/route/builder/GatewayFilterSpec.java

@@ -58,6 +58,7 @@
 import org.springframework.cloud.gateway.filter.factory.RemoveResponseHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RequestHeaderSizeGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RequestHeaderToRequestUriGatewayFilterFactory;
+import org.springframework.cloud.gateway.filter.factory.SetRequestUriGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RequestRateLimiterGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RequestSizeGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RetryGatewayFilterFactory;
@@ -869,6 +870,16 @@ public GatewayFilterSpec requestHeaderToRequestUri(String headerName) {
 		return filter(getBean(RequestHeaderToRequestUriGatewayFilterFactory.class).apply(c -> c.setName(headerName)));
 	}
 
+	/**
+	 * A filter which changes the URI the request will be routed to by the Gateway by
+	 * pulling it from a header on the request.
+	 * @param uri the URI
+	 * @return a {@link GatewayFilterSpec} that can be used to apply additional filters
+	 */
+	public GatewayFilterSpec setRequestUri(String uri) {
+		return filter(getBean(SetRequestUriGatewayFilterFactory.class).apply(c -> c.setTemplate(uri)));
+	}
+
 	/**
 	 * A filter which change the URI the request will be routed to by the Gateway.
 	 * @param determineRequestUri a {@link Function} which takes a

spring-cloud-gateway-server/src/test/java/org/springframework/cloud/gateway/filter/factory/SetRequestUriGatewayFilterFactoryIntegrationTests.java

@@ -0,0 +1,79 @@
+/*
+ * Copyright 2013-2020 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.cloud.gateway.filter.factory;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.SpringBootConfiguration;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.web.server.LocalServerPort;
+import org.springframework.cloud.gateway.route.RouteLocator;
+import org.springframework.cloud.gateway.route.builder.RouteLocatorBuilder;
+import org.springframework.cloud.gateway.test.BaseWebClientTests;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Import;
+import org.springframework.test.annotation.DirtiesContext;
+
+import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;
+
+/**
+ * @author Stepan Mikhailiuk
+ */
+@SpringBootTest(webEnvironment = RANDOM_PORT)
+@DirtiesContext
+public class SetRequestUriGatewayFilterFactoryIntegrationTests extends BaseWebClientTests {
+
+	@LocalServerPort
+	int port;
+
+	@Test
+	public void setUriWorkWithProperties() {
+		testClient.get().uri("/").header("Host", "testservice.setrequesturi.org").exchange().expectStatus().isOk();
+
+		testClient.get()
+			.uri("/service/testservice")
+			.header("Host", "setrequesturi.org")
+			.exchange()
+			.expectStatus()
+			.isOk();
+	}
+
+	@EnableAutoConfiguration
+	@SpringBootConfiguration
+	@Import(DefaultTestConfig.class)
+	public static class TestConfig {
+
+		@Bean
+		public RouteLocator routeLocator(RouteLocatorBuilder builder) {
+			return builder.routes()
+				.route("map_subdomain_to_service_name",
+						r -> r.host("{serviceName}.setrequesturi.org")
+							.filters(f -> f.prefixPath("/httpbin").setRequestUri("lb://{serviceName}"))
+							.uri("no://op"))
+				.route("map_path_to_service_name",
+						r -> r.host("setrequesturi.org")
+							.and()
+							.path("/service/{serviceName}")
+							.filters(f -> f.rewritePath("/.*", "/").setRequestUri("lb://{serviceName}"))
+							.uri("no://op"))
+				.build();
+		}
+
+	}
+
+}

spring-cloud-gateway-server/src/test/java/org/springframework/cloud/gateway/filter/factory/SetRequestUriGatewayFilterFactoryTests.java

@@ -0,0 +1,83 @@
+/*
+ * Copyright 2013-2020 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.cloud.gateway.filter.factory;
+
+import java.net.URI;
+
+import org.junit.jupiter.api.Test;
+import org.mockito.ArgumentCaptor;
+import reactor.core.publisher.Mono;
+
+import org.springframework.cloud.gateway.filter.GatewayFilter;
+import org.springframework.cloud.gateway.filter.GatewayFilterChain;
+import org.springframework.mock.http.server.reactive.MockServerHttpRequest;
+import org.springframework.mock.web.server.MockServerWebExchange;
+import org.springframework.web.server.ServerWebExchange;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR;
+
+/**
+ * @author Stepan Mikhailiuk
+ */
+public class SetRequestUriGatewayFilterFactoryTests {
+
+	@Test
+	public void filterChangeRequestUri() {
+		SetRequestUriGatewayFilterFactory factory = new SetRequestUriGatewayFilterFactory();
+		GatewayFilter filter = factory.apply(c -> c.setTemplate("https://example.com"));
+		MockServerHttpRequest request = MockServerHttpRequest.get("http://localhost").build();
+		ServerWebExchange exchange = MockServerWebExchange.from(request);
+		exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, URI.create("http://localhost"));
+		GatewayFilterChain filterChain = mock(GatewayFilterChain.class);
+		ArgumentCaptor<ServerWebExchange> captor = ArgumentCaptor.forClass(ServerWebExchange.class);
+		when(filterChain.filter(captor.capture())).thenReturn(Mono.empty());
+		filter.filter(exchange, filterChain);
+		ServerWebExchange webExchange = captor.getValue();
+		URI uri = (URI) webExchange.getAttributes().get(GATEWAY_REQUEST_URL_ATTR);
+		assertThat(uri).isNotNull();
+		assertThat(uri.toString()).isEqualTo("https://example.com");
+	}
+
+	@Test
+	public void filterDoesNotChangeRequestUriIfUriIsInvalid() throws Exception {
+		SetRequestUriGatewayFilterFactory factory = new SetRequestUriGatewayFilterFactory();
+		GatewayFilter filter = factory.apply(c -> c.setTemplate("invalid_uri"));
+		MockServerHttpRequest request = MockServerHttpRequest.get("http://localhost").build();
+		ServerWebExchange exchange = MockServerWebExchange.from(request);
+		exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, URI.create("http://localhost"));
+		GatewayFilterChain filterChain = mock(GatewayFilterChain.class);
+		ArgumentCaptor<ServerWebExchange> captor = ArgumentCaptor.forClass(ServerWebExchange.class);
+		when(filterChain.filter(captor.capture())).thenReturn(Mono.empty());
+		filter.filter(exchange, filterChain);
+		ServerWebExchange webExchange = captor.getValue();
+		URI uri = (URI) webExchange.getAttributes().get(GATEWAY_REQUEST_URL_ATTR);
+		assertThat(uri).isNotNull();
+		assertThat(uri.toURL().toString()).isEqualTo("http://localhost");
+	}
+
+	@Test
+	public void toStringFormat() {
+		SetRequestUriGatewayFilterFactory.Config config = new SetRequestUriGatewayFilterFactory.Config();
+		config.setTemplate("http://localhost:8080");
+		GatewayFilter filter = new SetRequestUriGatewayFilterFactory().apply(config);
+		assertThat(filter.toString()).contains("http://localhost:8080");
+	}
+
+}

spring-cloud-gateway-server/src/test/java/org/springframework/cloud/gateway/test/AdhocTestSuite.java

@@ -66,6 +66,8 @@
 		RewriteLocationResponseHeaderGatewayFilterFactoryTests.class,
 		org.springframework.cloud.gateway.filter.factory.RequestRateLimiterGatewayFilterFactoryTests.class,
 		org.springframework.cloud.gateway.filter.factory.RequestHeaderToRequestUriGatewayFilterFactoryIntegrationTests.class,
+		org.springframework.cloud.gateway.filter.factory.SetRequestUriGatewayFilterFactoryTests.class,
+		org.springframework.cloud.gateway.filter.factory.SetRequestUriGatewayFilterFactoryIntegrationTests.class,
 		org.springframework.cloud.gateway.filter.factory.RemoveResponseHeaderGatewayFilterFactoryTests.class,
 		org.springframework.cloud.gateway.filter.factory.RewritePathGatewayFilterFactoryTests.class,
 		org.springframework.cloud.gateway.filter.factory.StripPrefixGatewayFilterFactoryIntegrationTests.class,