Supports relative uri in RedirectTo filter

fixes gh-468

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/factory/RedirectToGatewayFilterFactory.java

@@ -59,16 +59,11 @@ public class RedirectToGatewayFilterFactory extends AbstractGatewayFilterFactory
 	public GatewayFilter apply(String statusString, String urlString) {
 		final HttpStatus httpStatus = parse(statusString);
 		Assert.isTrue(httpStatus.is3xxRedirection(), "status must be a 3xx code, but was " + statusString);
-		final URL url;
-		try {
-			url = URI.create(urlString).toURL();
-		} catch (MalformedURLException e) {
-			throw new IllegalArgumentException("Invalid url " + urlString, e);
-		}
+		final URI url = URI.create(urlString);
 		return apply(httpStatus, url);
 	}
 
-	public GatewayFilter apply(HttpStatus httpStatus, URL url) {
+	public GatewayFilter apply(HttpStatus httpStatus, URI uri) {
 
 		return (exchange, chain) ->
 			chain.filter(exchange).then(Mono.defer(() -> {
@@ -76,7 +71,7 @@ public class RedirectToGatewayFilterFactory extends AbstractGatewayFilterFactory
 					setResponseStatus(exchange, httpStatus);
 
 					final ServerHttpResponse response = exchange.getResponse();
-					response.getHeaders().set(HttpHeaders.LOCATION, url.toString());
+					response.getHeaders().set(HttpHeaders.LOCATION, uri.toString());
 					return response.setComplete();
 				}
 				return Mono.empty();

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

@@ -17,6 +17,7 @@
 package org.springframework.cloud.gateway.route.builder;
 
 import java.net.URI;
+import java.net.URISyntaxException;
 import java.net.URL;
 import java.util.Collection;
 import java.util.Optional;
@@ -266,7 +267,7 @@ public class GatewayFilterSpec extends UriSpec {
 	 * @return a {@link GatewayFilterSpec} that can be used to apply additional filters
 	 */
 	public GatewayFilterSpec redirect(String status, URI url) {
-		return redirect(status, url.toString());
+		return redirect(status, url);
 	}
 
 	/**
@@ -286,7 +287,11 @@ public class GatewayFilterSpec extends UriSpec {
 	 * @return a {@link GatewayFilterSpec} that can be used to apply additional filters
 	 */
 	public GatewayFilterSpec redirect(HttpStatus status, URL url) {
-		return filter(getBean(RedirectToGatewayFilterFactory.class).apply(status, url));
+		try {
+			return filter(getBean(RedirectToGatewayFilterFactory.class).apply(status, url.toURI()));
+		} catch (URISyntaxException e) {
+			throw new IllegalArgumentException("Invalid URL", e);
+		}
 	}
 
 	/**

spring-cloud-gateway-core/src/test/java/org/springframework/cloud/gateway/filter/factory/RedirectToGatewayFilterFactoryTests.java

@@ -22,7 +22,10 @@ import org.junit.runner.RunWith;
 import org.springframework.boot.SpringBootConfiguration;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.test.context.SpringBootTest;
+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.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
@@ -46,9 +49,29 @@ public class RedirectToGatewayFilterFactoryTests extends BaseWebClientTests {
 				.expectHeader().valueEquals(HttpHeaders.LOCATION, "http://example.org");
 	}
 
+	@Test
+	public void redirectToRelativeUrlFilterWorks() {
+		testClient.get()
+				.uri("/")
+				.header("Host", "www.relativeredirect.org")
+				.exchange()
+				.expectStatus().isEqualTo(HttpStatus.FOUND)
+				.expectHeader().valueEquals(HttpHeaders.LOCATION, "/index.html#/customers");
+	}
+
 	@EnableAutoConfiguration
 	@SpringBootConfiguration
 	@Import(DefaultTestConfig.class)
-	public static class TestConfig { }
+	public static class TestConfig {
+
+		@Bean
+		public RouteLocator testRouteLocator(RouteLocatorBuilder builder) {
+			return builder.routes()
+					.route("relative_redirect", r -> r.host("**.relativeredirect.org")
+							.filters(f -> f.redirect(302, "/index.html#/customers"))
+							.uri("no://op"))
+					.build();
+		}
+	}
 
 }