Support query parameters in RedirectTo filter

Adds an optional boolean parameter to the RedirectTo filter to indicate whether the request query parameters should be included on the `url`. The parameter is treated as false when not set to preserve backwards compatibility.

Author: Fredrich Ombico

docs/src/main/asciidoc/spring-cloud-gateway.adoc

@@ -1242,10 +1242,12 @@ spring:
 
 === The `RedirectTo` `GatewayFilter` Factory
 
-The `RedirectTo` `GatewayFilter` factory takes two parameters, `status` and `url`.
+The `RedirectTo` `GatewayFilter` factory takes three parameters, `status`, `url`, and optionally `includeRequestParams`.
 The `status` parameter should be a 300 series redirect HTTP code, such as 301.
 The `url` parameter should be a valid URL.
 This is the value of the `Location` header.
+The `includeRequestParams` parameter indicates whether request query parameters should be included on the `url`.
+When not set, it will be treated as `false`.
 For relative redirects, you should use `uri: no://op` as the uri of your route definition.
 The following listing configures a `RedirectTo` `GatewayFilter`:
 
@@ -1266,6 +1268,24 @@ spring:
 
 This will send a status 302 with a `Location:https://acme.org` header to perform a redirect.
 
+The following example configures a `RedirectTo` `GatewayFilter` with `includeRequestParams` set to `true`.
+
+.application.yml
+[source,yaml]
+----
+spring:
+  cloud:
+    gateway:
+      routes:
+      - id: prefixpath_route
+        uri: https://example.org
+        filters:
+        - RedirectTo=302, https://acme.org, true
+----
+
+When a request with query `?skip=10` is made to the gateway, the gateway will send a status 302 with a
+`Location:https://acme.org?skip=10` header to perform a redirect.
+
 
 === `RemoveJsonAttributesResponseBody` `GatewayFilter` Factory
 

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

@@ -30,6 +30,7 @@
 import org.springframework.http.server.reactive.ServerHttpResponse;
 import org.springframework.util.Assert;
 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.setResponseStatus;
@@ -50,40 +51,66 @@ public class RedirectToGatewayFilterFactory
 	 */
 	public static final String URL_KEY = "url";
 
+	/**
+	 * IncludeRequestParams key.
+	 */
+	public static final String INCLUDE_REQUEST_PARAMS_KEY = "includeRequestParams";
+
 	public RedirectToGatewayFilterFactory() {
 		super(Config.class);
 	}
 
 	@Override
 	public List<String> shortcutFieldOrder() {
-		return Arrays.asList(STATUS_KEY, URL_KEY);
+		return Arrays.asList(STATUS_KEY, URL_KEY, INCLUDE_REQUEST_PARAMS_KEY);
 	}
 
 	@Override
 	public GatewayFilter apply(Config config) {
-		return apply(config.status, config.url);
+		return apply(config.status, config.url, config.includeRequestParams);
 	}
 
 	public GatewayFilter apply(String statusString, String urlString) {
+		return apply(statusString, urlString, false);
+	}
+
+	public GatewayFilter apply(String statusString, String urlString, boolean includeRequestParams) {
 		HttpStatusHolder httpStatus = HttpStatusHolder.parse(statusString);
 		Assert.isTrue(httpStatus.is3xxRedirection(), "status must be a 3xx code, but was " + statusString);
 		final URI url = URI.create(urlString);
-		return apply(httpStatus, url);
+		return apply(httpStatus, url, includeRequestParams);
 	}
 
 	public GatewayFilter apply(HttpStatus httpStatus, URI uri) {
-		return apply(new HttpStatusHolder(httpStatus, null), uri);
+		return apply(new HttpStatusHolder(httpStatus, null), uri, false);
+	}
+
+	public GatewayFilter apply(HttpStatus httpStatus, URI uri, boolean includeRequestParams) {
+		return apply(new HttpStatusHolder(httpStatus, null), uri, includeRequestParams);
 	}
 
 	public GatewayFilter apply(HttpStatusHolder httpStatus, URI uri) {
+		return apply(httpStatus, uri, false);
+	}
+
+	public GatewayFilter apply(HttpStatusHolder httpStatus, URI uri, boolean includeRequestParams) {
 		return new GatewayFilter() {
 			@Override
 			public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
 				if (!exchange.getResponse().isCommitted()) {
 					setResponseStatus(exchange, httpStatus);
 
+					String location;
+					if (includeRequestParams) {
+						location = UriComponentsBuilder.fromUri(uri).queryParams(exchange.getRequest().getQueryParams())
+								.build().toUri().toString();
+					}
+					else {
+						location = uri.toString();
+					}
+
 					final ServerHttpResponse response = exchange.getResponse();
-					response.getHeaders().set(HttpHeaders.LOCATION, uri.toString());
+					response.getHeaders().set(HttpHeaders.LOCATION, location);
 					return response.setComplete();
 				}
 				return Mono.empty();
@@ -98,7 +125,8 @@ public String toString() {
 				else {
 					status = httpStatus.getStatus().toString();
 				}
-				return filterToStringCreator(RedirectToGatewayFilterFactory.this).append(status, uri).toString();
+				return filterToStringCreator(RedirectToGatewayFilterFactory.this).append(status, uri)
+						.append(INCLUDE_REQUEST_PARAMS_KEY, includeRequestParams).toString();
 			}
 		};
 	}
@@ -109,6 +137,8 @@ public static class Config {
 
 		String url;
 
+		boolean includeRequestParams;
+
 		public String getStatus() {
 			return status;
 		}
@@ -125,6 +155,14 @@ public void setUrl(String url) {
 			this.url = url;
 		}
 
+		public boolean isIncludeRequestParams() {
+			return includeRequestParams;
+		}
+
+		public void setIncludeRequestParams(boolean includeRequestParams) {
+			this.includeRequestParams = includeRequestParams;
+		}
+
 	}
 
 }

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

@@ -435,6 +435,18 @@ public GatewayFilterSpec redirect(int status, URI url) {
 		return redirect(String.valueOf(status), url.toString());
 	}
 
+	/**
+	 * A filter that will return a redirect response back to the client.
+	 * @param status an HTTP status code, should be a {@code 300} series redirect
+	 * @param url the URL to redirect to. This URL will be set in the {@code location}
+	 * header
+	 * @param includeRequestParams if true, query params will be passed to the url
+	 * @return a {@link GatewayFilterSpec} that can be used to apply additional filters
+	 */
+	public GatewayFilterSpec redirect(int status, URI url, boolean includeRequestParams) {
+		return redirect(String.valueOf(status), url.toString(), includeRequestParams);
+	}
+
 	/**
 	 * A filter that will return a redirect response back to the client.
 	 * @param status an HTTP status code, should be a {@code 300} series redirect
@@ -446,6 +458,18 @@ public GatewayFilterSpec redirect(int status, String url) {
 		return redirect(String.valueOf(status), url);
 	}
 
+	/**
+	 * A filter that will return a redirect response back to the client.
+	 * @param status an HTTP status code, should be a {@code 300} series redirect
+	 * @param url the URL to redirect to. This URL will be set in the {@code location}
+	 * header
+	 * @param includeRequestParams if true, query params will be passed to the url
+	 * @return a {@link GatewayFilterSpec} that can be used to apply additional filters
+	 */
+	public GatewayFilterSpec redirect(int status, String url, boolean includeRequestParams) {
+		return redirect(String.valueOf(status), url, includeRequestParams);
+	}
+
 	/**
 	 * A filter that will return a redirect response back to the client.
 	 * @param status an HTTP status code, should be a {@code 300} series redirect
@@ -454,7 +478,19 @@ public GatewayFilterSpec redirect(int status, String url) {
 	 * @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.toString(), false);
+	}
+
+	/**
+	 * A filter that will return a redirect response back to the client.
+	 * @param status an HTTP status code, should be a {@code 300} series redirect
+	 * @param url the URL to redirect to. This URL will be set in the {@code location}
+	 * header
+	 * @param includeRequestParams if true, query params will be passed to the url
+	 * @return a {@link GatewayFilterSpec} that can be used to apply additional filters
+	 */
+	public GatewayFilterSpec redirect(String status, String url, boolean includeRequestParams) {
+		return filter(getBean(RedirectToGatewayFilterFactory.class).apply(status, url, includeRequestParams));
 	}
 
 	/**
@@ -476,8 +512,21 @@ public GatewayFilterSpec redirect(String status, String url) {
 	 * @return a {@link GatewayFilterSpec} that can be used to apply additional filters
 	 */
 	public GatewayFilterSpec redirect(HttpStatus status, URL url) {
+		return redirect(status, url, false);
+	}
+
+	/**
+	 * A filter that will return a redirect response back to the client.
+	 * @param status an HTTP status code, should be a {@code 300} series redirect
+	 * @param url the URL to redirect to. This URL will be set in the {@code location}
+	 * header
+	 * @param includeRequestParams if true, query params will be passed to the url
+	 * @return a {@link GatewayFilterSpec} that can be used to apply additional filters
+	 */
+	public GatewayFilterSpec redirect(HttpStatus status, URL url, boolean includeRequestParams) {
 		try {
-			return filter(getBean(RedirectToGatewayFilterFactory.class).apply(status, url.toURI()));
+			return filter(
+					getBean(RedirectToGatewayFilterFactory.class).apply(status, url.toURI(), includeRequestParams));
 		}
 		catch (URISyntaxException e) {
 			throw new IllegalArgumentException("Invalid URL", e);

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

@@ -47,6 +47,19 @@ public void redirectToFilterWorks() {
 				.isEqualTo(HttpStatus.FOUND).expectHeader().valueEquals(HttpHeaders.LOCATION, "https://example.org");
 	}
 
+	@Test
+	public void redirectToUrlDoesNotPassQueryParametersByDefault() {
+		testClient.get().uri("/?membership=gold").header("Host", "www.redirectto.org").exchange().expectStatus()
+				.isEqualTo(HttpStatus.FOUND).expectHeader().valueEquals(HttpHeaders.LOCATION, "https://example.org");
+	}
+
+	@Test
+	public void redirectToUrlAddsQueryParametersWhenEnabledOnFilter() {
+		testClient.get().uri("/?membership=gold").header("Host", "queryparams.redirectto.org").exchange().expectStatus()
+				.isEqualTo(HttpStatus.FOUND).expectHeader()
+				.valueEquals(HttpHeaders.LOCATION, "https://example.org?membership=gold");
+	}
+
 	@Test
 	public void redirectToRelativeUrlFilterWorks() {
 		testClient.get().uri("/").header("Host", "www.relativeredirect.org").exchange().expectStatus()
@@ -59,13 +72,27 @@ public void redirectToRelativeUrlFilterWorksWithStrStatusCode() {
 				.isEqualTo(HttpStatus.FOUND).expectHeader().valueEquals(HttpHeaders.LOCATION, "/index.html#/customers");
 	}
 
+	@Test
+	public void redirectToRelativeUrlDoesNotPassQueryParametersByDefault() {
+		testClient.get().uri("/?membership=gold").header("Host", "www.relativeredirect.org").exchange().expectStatus()
+				.isEqualTo(HttpStatus.FOUND).expectHeader().valueEquals(HttpHeaders.LOCATION, "/index.html#/customers");
+	}
+
+	@Test
+	public void redirectToRelativeUrlAddsQueryParametersWhenEnabledOnFilter() {
+		testClient.get().uri("/?membership=gold").header("Host", "queryparams.relativeredirect.org").exchange()
+				.expectStatus().isEqualTo(HttpStatus.FOUND).expectHeader()
+				.valueEquals(HttpHeaders.LOCATION, "/index.html?membership=gold#/customers");
+	}
+
 	@Test
 	public void toStringFormat() {
 		Config config = new Config();
 		config.setStatus("301");
 		config.setUrl("http://newurl");
+		config.setIncludeRequestParams(true);
 		GatewayFilter filter = new RedirectToGatewayFilterFactory().apply(config);
-		assertThat(filter.toString()).contains("301").contains("http://newurl");
+		assertThat(filter.toString()).contains("301").contains("http://newurl").contains("true");
 	}
 
 	@EnableAutoConfiguration
@@ -78,6 +105,9 @@ public RouteLocator testRouteLocator(RouteLocatorBuilder builder) {
 			return builder.routes()
 					.route("relative_redirect_uri_object", r -> r.host("strcode.relativeredirect.org")
 							.filters(f -> f.redirect("302", URI.create("/index.html#/customers"))).uri("no://op"))
+					.route("relative_redirect_with_query_params",
+							r -> r.host("queryparams.relativeredirect.org")
+									.filters(f -> f.redirect(302, "/index.html#/customers", true)).uri("no://op"))
 					.route("relative_redirect", r -> r.host("**.relativeredirect.org")
 							.filters(f -> f.redirect(302, "/index.html#/customers")).uri("no://op"))
 					.build();

spring-cloud-gateway-server/src/test/resources/application.yml

@@ -296,6 +296,14 @@ spring:
         filters:
           - SetPath=/anything/{digits}
 
+        # =====================================
+      - id: redirect_to_include_query_params_test
+        uri: ${test.uri}
+        predicates:
+          - Host=queryparams.redirectto.org
+        filters:
+          - RedirectTo=302, https://example.org, true
+
       # =====================================
       - id: redirect_to_test
         uri: ${test.uri}