Add RewriteRequestParameter GatewayFilter factory (#3081)

The `RewriteRequestParameter` `GatewayFilter` factory takes a `name` parameter and a `replacement` parameter.
It will rewrite the value of the request parameter of the given `name`.

docs/src/main/asciidoc/_configprops.adoc

@@ -43,6 +43,7 @@
 |spring.cloud.gateway.filter.rewrite-location-response-header.enabled | `+++true+++` | Enables the rewrite-location-response-header filter.
 |spring.cloud.gateway.filter.rewrite-location.enabled | `+++true+++` | Enables the rewrite-location filter.
 |spring.cloud.gateway.filter.rewrite-path.enabled | `+++true+++` | Enables the rewrite-path filter.
+|spring.cloud.gateway.filter.rewrite-request-parameter.enabled | `+++true+++` | Enables the rewrite-request-parameter filter.
 |spring.cloud.gateway.filter.rewrite-response-header.enabled | `+++true+++` | Enables the rewrite-response-header filter.
 |spring.cloud.gateway.filter.save-session.enabled | `+++true+++` | Enables the save-session filter.
 |spring.cloud.gateway.filter.secure-headers.content-security-policy | `+++default-src 'self' https:; font-src 'self' https: data:; img-src 'self' https: data:; object-src 'none'; script-src https:; style-src 'self' https: 'unsafe-inline'+++` | 

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

@@ -1598,6 +1598,34 @@ spring:
 
 For a request path of `/red/blue`, this sets the path to `/blue` before making the downstream request. Note that the `$` should be replaced with `$\` because of the YAML specification.
 
+=== The `RewriteRequestParameter` `GatewayFilter` Factory
+
+The `RewriteRequestParameter` `GatewayFilter` factory takes a `name` parameter and a `replacement` parameter.
+It will rewrite the value of the request parameter of the given `name`.
+If multiple request parameters with the same `name` are set, they will be replaced with a single value.
+If no request parameter is found, no changes will be made.
+The following listing configures a `RewriteRequestParameter` `GatewayFilter`:
+
+.application.yml
+====
+[source,yaml]
+----
+spring:
+  cloud:
+    gateway:
+      routes:
+      - id: rewriterequestparameter_route
+        uri: https://example.org
+        predicates:
+        - Path=/products
+        filters:
+        - RewriteRequestParameter=campaign,fall2023
+----
+====
+
+For a request to `/products?campaign=old`, this sets the request parameter to `campaign=fall2023`.
+
+
 === The `RewriteResponseHeader` `GatewayFilter` Factory
 
 The `RewriteResponseHeader` `GatewayFilter` factory takes `name`, `regexp`, and `replacement` parameters.

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

@@ -97,6 +97,7 @@ import org.springframework.cloud.gateway.filter.factory.RequestSizeGatewayFilter
 import org.springframework.cloud.gateway.filter.factory.RetryGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RewriteLocationResponseHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RewritePathGatewayFilterFactory;
+import org.springframework.cloud.gateway.filter.factory.RewriteRequestParameterGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RewriteResponseHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SaveSessionGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SecureHeadersGatewayFilterFactory;
@@ -703,6 +704,12 @@ public class GatewayAutoConfiguration {
 		return new RequestHeaderSizeGatewayFilterFactory();
 	}
 
+	@Bean
+	@ConditionalOnEnabledFilter
+	public RewriteRequestParameterGatewayFilterFactory rewriteRequestParameterGatewayFilterFactory() {
+		return new RewriteRequestParameterGatewayFilterFactory();
+	}
+
 	@Bean
 	public GzipMessageBodyResolver gzipMessageBodyResolver() {
 		return new GzipMessageBodyResolver();

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

@@ -0,0 +1,96 @@
+/*
+ * Copyright 2013-2023 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 reactor.core.publisher.Mono;
+
+import org.springframework.cloud.gateway.filter.GatewayFilter;
+import org.springframework.cloud.gateway.filter.GatewayFilterChain;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+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;
+
+/**
+ * @author Fredrich Ombico
+ */
+public class RewriteRequestParameterGatewayFilterFactory
+		extends AbstractGatewayFilterFactory<RewriteRequestParameterGatewayFilterFactory.Config> {
+
+	/**
+	 * Replacement key.
+	 */
+	public static final String REPLACEMENT_KEY = "replacement";
+
+	public RewriteRequestParameterGatewayFilterFactory() {
+		super(Config.class);
+	}
+
+	@Override
+	public List<String> shortcutFieldOrder() {
+		return Arrays.asList(NAME_KEY, REPLACEMENT_KEY);
+	}
+
+	@Override
+	public GatewayFilter apply(Config config) {
+		return new GatewayFilter() {
+			@Override
+			public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
+				ServerHttpRequest req = exchange.getRequest();
+
+				UriComponentsBuilder uriComponentsBuilder = UriComponentsBuilder.fromUri(req.getURI());
+				if (req.getQueryParams().containsKey(config.getName())) {
+					uriComponentsBuilder.replaceQueryParam(config.getName(), config.getReplacement());
+				}
+
+				URI uri = uriComponentsBuilder.build().toUri();
+				ServerHttpRequest request = req.mutate().uri(uri).build();
+
+				return chain.filter(exchange.mutate().request(request).build());
+			}
+
+			@Override
+			public String toString() {
+				return filterToStringCreator(RewriteRequestParameterGatewayFilterFactory.this)
+						.append(config.getName(), config.replacement).toString();
+			}
+		};
+	}
+
+	public static class Config extends AbstractGatewayFilterFactory.NameConfig {
+
+		private String replacement;
+
+		public String getReplacement() {
+			return replacement;
+		}
+
+		public Config setReplacement(String replacement) {
+			Assert.notNull(replacement, "replacement must not be null");
+			this.replacement = replacement;
+			return this;
+		}
+
+	}
+
+}

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

@@ -64,6 +64,7 @@ import org.springframework.cloud.gateway.filter.factory.RetryGatewayFilterFactor
 import org.springframework.cloud.gateway.filter.factory.RewriteLocationResponseHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RewriteLocationResponseHeaderGatewayFilterFactory.StripVersion;
 import org.springframework.cloud.gateway.filter.factory.RewritePathGatewayFilterFactory;
+import org.springframework.cloud.gateway.filter.factory.RewriteRequestParameterGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RewriteResponseHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SaveSessionGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SecureHeadersGatewayFilterFactory;
@@ -686,6 +687,17 @@ public class GatewayFilterSpec extends UriSpec {
 						.setHostValue(hostValue).setProtocols(protocolsRegex)));
 	}
 
+	/**
+	 * A filter that rewrites the value of a request parameter
+	 * @param name The name of the request parameter to replace
+	 * @param replacement The new value for the request parameter
+	 * @return a {@link GatewayFilterSpec} that can be used to apply additional filters
+	 */
+	public GatewayFilterSpec rewriteRequestParameter(String name, String replacement) {
+		return filter(getBean(RewriteRequestParameterGatewayFilterFactory.class)
+				.apply(c -> c.setReplacement(replacement).setName(name)));
+	}
+
 	/**
 	 * A filter that sets the status on the response before it is returned to the client
 	 * by the Gateway.

spring-cloud-gateway-server/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -167,6 +167,12 @@
       "description": "Enables the rewrite-location filter.",
       "defaultValue": "true"
     },
+    {
+      "name": "spring.cloud.gateway.filter.rewrite-request-parameter.enabled",
+      "type": "java.lang.Boolean",
+      "description": "Enables the rewrite-request-parameter filter.",
+      "defaultValue": "true"
+    },
     {
       "name": "spring.cloud.gateway.filter.set-status.enabled",
       "type": "java.lang.Boolean",

spring-cloud-gateway-server/src/test/java/org/springframework/cloud/gateway/config/conditional/DisableBuiltInFiltersTests.java

@@ -103,6 +103,7 @@ public class DisableBuiltInFiltersTests {
 					"spring.cloud.gateway.filter.rewrite-response-header.enabled=false",
 					"spring.cloud.gateway.filter.rewrite-location-response-header.enabled=false",
 					"spring.cloud.gateway.filter.rewrite-location.enabled=false",
+					"spring.cloud.gateway.filter.rewrite-request-parameter.enabled=false",
 					"spring.cloud.gateway.filter.set-status.enabled=false",
 					"spring.cloud.gateway.filter.save-session.enabled=false",
 					"spring.cloud.gateway.filter.strip-prefix.enabled=false",

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

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2013-2023 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.cloud.gateway.test.BaseWebClientTests;
+import org.springframework.context.annotation.Import;
+import org.springframework.test.annotation.DirtiesContext;
+
+import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;
+
+/**
+ * @author Fredrich Ombico
+ */
+@SpringBootTest(webEnvironment = RANDOM_PORT)
+@DirtiesContext
+class RewriteRequestParameterGatewayFilterFactoryIntegrationTests extends BaseWebClientTests {
+
+	@Test
+	void rewriteRequestParameterFilterWorks() {
+		testClient.get().uri("/get?campaign=old").header("Host", "www.rewriterequestparameter.org").exchange()
+				.expectStatus().isOk().expectBody().jsonPath("$.args.size", "fall2023");
+	}
+
+	@EnableAutoConfiguration
+	@SpringBootConfiguration
+	@Import(DefaultTestConfig.class)
+	public static class TestConfig {
+
+	}
+
+}

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

@@ -0,0 +1,102 @@
+/*
+ * Copyright 2013-2023 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.List;
+import java.util.Map;
+
+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.http.HttpMethod;
+import org.springframework.mock.http.server.reactive.MockServerHttpRequest;
+import org.springframework.mock.web.server.MockServerWebExchange;
+import org.springframework.util.MultiValueMap;
+import org.springframework.web.server.ServerWebExchange;
+import org.springframework.web.util.UriComponentsBuilder;
+
+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.filter.factory.RewriteRequestParameterGatewayFilterFactory.Config;
+
+/**
+ * @author Fredrich Ombico
+ */
+class RewriteRequestParameterGatewayFilterFactoryTests {
+
+	@Test
+	void toStringFormat() {
+		Config config = new Config();
+		config.setName("campaign");
+		config.setReplacement("fall2023");
+		GatewayFilter filter = new RewriteRequestParameterGatewayFilterFactory().apply(config);
+		assertThat(filter.toString()).contains("campaign").contains("fall2023");
+	}
+
+	@Test
+	void rewriteRequestParameterFilterWorks() {
+		testRewriteRequestParameterFilter("campaign", "fall2023", "size=small&campaign=old",
+				Map.of("size", List.of("small"), "campaign", List.of("fall2023")));
+	}
+
+	@Test
+	void rewriteRequestParameterFilterRewritesMultipleParamsWithSameName() {
+		testRewriteRequestParameterFilter("campaign", "fall2023", "campaign=fall&size=small&campaign=old",
+				Map.of("size", List.of("small"), "campaign", List.of("fall2023")));
+	}
+
+	@Test
+	void rewriteRequestParameterFilterDoesNotAddParamIfNameNotFound() {
+		testRewriteRequestParameterFilter("campaign", "winter2023", "color=green&sort=popular",
+				Map.of("color", List.of("green"), "sort", List.of("popular")));
+	}
+
+	@Test
+	void rewriteRequestParameterFilterWorksWithSpecialCharacters() {
+		testRewriteRequestParameterFilter("campaign", "black friday~(1.A-B_C!)", "campaign=old&color=green",
+				Map.of("campaign", List.of("black friday~(1.A-B_C!)"), "color", List.of("green")));
+	}
+
+	private void testRewriteRequestParameterFilter(String name, String replacement, String query,
+			Map<String, List<String>> expectedQueryParams) {
+		GatewayFilter filter = new RewriteRequestParameterGatewayFilterFactory()
+				.apply(config -> config.setReplacement(replacement).setName(name));
+
+		URI url = UriComponentsBuilder.fromUriString("http://localhost/get").query(query).build(true).toUri();
+		MockServerHttpRequest request = MockServerHttpRequest.method(HttpMethod.GET, url).build();
+
+		ServerWebExchange exchange = MockServerWebExchange.from(request);
+
+		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();
+
+		MultiValueMap<String, String> actualQueryParams = webExchange.getRequest().getQueryParams();
+		assertThat(actualQueryParams).containsExactlyInAnyOrderEntriesOf(expectedQueryParams);
+	}
+
+}

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

@@ -341,6 +341,14 @@ spring:
           - RewriteLocationResponseHeader
           - AddResponseHeader=Location, https://backend.org:443/v1/some/object/id
 
+        # =====================================
+      - id: rewrite_request_parameter_test
+        uri: ${test.uri}
+        predicates:
+          - Host=**.rewriterequestparameter.org
+        filters:
+          - RewriteRequestParameter=campaign,fall2023
+
         # =====================================
       - id: rewrite_response_header_test
         uri: ${test.uri}