Stop double-encoding path in stripPrefix

Fixes spring-cloudgh-3436

spring-cloud-gateway-server-mvc/src/main/java/org/springframework/cloud/gateway/server/mvc/filter/BeforeFilterFunctions.java

@@ -398,7 +398,7 @@ public static Function<ServerRequest, ServerRequest> stripPrefix(int parts) {
 			}
 			// TODO: end duplicate code from StripPrefixGatewayFilterFactory
 
-			URI prefixedUri = UriComponentsBuilder.fromUri(request.uri()).replacePath(newPath.toString()).build()
+			URI prefixedUri = UriComponentsBuilder.fromUri(request.uri()).replacePath(newPath.toString()).build(true)
 					.toUri();
 			return ServerRequest.from(request).uri(prefixedUri).build();
 		};

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

@@ -225,6 +225,15 @@ public void stripPrefixWorks() {
 				});
 	}
 
+	@Test
+	public void stripPrefixWorksWithEncoding() {
+		restClient.get().uri("/long/path/to/anything/anything goes").exchange().expectStatus().isOk()
+				.expectBody(Map.class).consumeWith(res -> {
+					Map<String, Object> map = res.getResponseBody();
+					assertThat(map.get("url")).asString().endsWith("anything%20goes");
+				});
+	}
+
 	@Test
 	public void stripPrefixPostWorks() {
 		restClient.post().uri("/long/path/to/post").bodyValue("hello").header("Host", "www.stripprefixpost.org")
@@ -815,6 +824,17 @@ public RouterFunction<ServerResponse> gatewayRouterFunctionsStripPrefix() {
 			// @formatter:on
 		}
 
+		@Bean
+		public RouterFunction<ServerResponse> gatewayRouterFunctionsStripPrefixWithEncoding() {
+			// @formatter:off
+			return route(GET("/long/path/to/anything/anything goes"), http())
+					.filter(new HttpbinUriResolver())
+					.filter(stripPrefix(3))
+					.filter(addRequestHeader("X-Test", "stripPrefix"))
+					.withAttribute(MvcUtils.GATEWAY_ROUTE_ID_ATTR, "teststripprefix");
+			// @formatter:on
+		}
+
 		@Bean
 		public RouterFunction<ServerResponse> gatewayRouterFunctionsStripPrefixPost() {
 			// @formatter:off