Adds BeforeFilterFunctions.addRequestHeadersIfNotPresent()

See gh-2949

spring-cloud-gateway-server-mvc/src/main/java/org/springframework/cloud/gateway/server/mvc/common/KeyValues.java

@@ -0,0 +1,79 @@
+/*
+ * 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.server.mvc.common;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import org.springframework.core.style.ToStringCreator;
+import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
+
+public class KeyValues {
+
+	private List<KeyValue> keyValues = new ArrayList<>();
+
+	public List<KeyValue> getKeyValues() {
+		return keyValues;
+	}
+
+	public void setKeyValues(List<KeyValue> keyValues) {
+		this.keyValues = keyValues;
+	}
+
+	public static KeyValues valueOf(String s) {
+		String[] tokens = StringUtils.tokenizeToStringArray(s, ",", true, true);
+		List<KeyValue> parsedKeyValues = Arrays.stream(tokens).map(KeyValue::valueOf).toList();
+		KeyValues keyValues = new KeyValues();
+		keyValues.setKeyValues(parsedKeyValues);
+		return keyValues;
+	}
+
+	public static class KeyValue {
+
+		private final String key;
+
+		private final String value;
+
+		public KeyValue(String key, String value) {
+			this.key = key;
+			this.value = value;
+		}
+
+		public String getKey() {
+			return key;
+		}
+
+		public String getValue() {
+			return value;
+		}
+
+		@Override
+		public String toString() {
+			return new ToStringCreator(this).append("name", key).append("value", value).toString();
+		}
+
+		public static KeyValue valueOf(String s) {
+			String[] tokens = StringUtils.tokenizeToStringArray(s, ":", true, true);
+			Assert.isTrue(tokens.length == 2, () -> "String must be two tokens delimited by colon, but was " + s);
+			return new KeyValue(tokens[0], tokens[1]);
+		}
+
+	}
+
+}

spring-cloud-gateway-server-mvc/src/main/java/org/springframework/cloud/gateway/server/mvc/common/MvcUtils.java

@@ -18,6 +18,7 @@ package org.springframework.cloud.gateway.server.mvc.common;
 
 import java.net.URI;
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -67,6 +68,10 @@ public abstract class MvcUtils {
 		return UriComponentsBuilder.fromPath(template).build().expand(variables).getPath();
 	}
 
+	public static List<String> expandMultiple(ServerRequest request, Collection<String> templates) {
+		return templates.stream().map(value -> MvcUtils.expand(request, value)).toList();
+	}
+
 	public static String[] expandMultiple(ServerRequest request, String... templates) {
 		List<String> expanded = Arrays.stream(templates).map(value -> MvcUtils.expand(request, value)).toList();
 		return expanded.toArray(new String[0]);

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

@@ -18,6 +18,7 @@ package org.springframework.cloud.gateway.server.mvc.filter;
 
 import java.net.URI;
 import java.net.URISyntaxException;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -27,6 +28,7 @@ import java.util.regex.Pattern;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
+import org.springframework.cloud.gateway.server.mvc.common.KeyValues.KeyValue;
 import org.springframework.cloud.gateway.server.mvc.common.MvcUtils;
 import org.springframework.core.log.LogMessage;
 import org.springframework.http.HttpHeaders;
@@ -64,6 +66,30 @@ public abstract class BeforeFilterFunctions {
 		};
 	}
 
+	public static Function<ServerRequest, ServerRequest> addRequestHeadersIfNotPresent(String... values) {
+		List<KeyValue> keyValues = Arrays.stream(values).map(KeyValue::valueOf).toList();
+		return addRequestHeadersIfNotPresent(keyValues);
+	}
+
+	public static Function<ServerRequest, ServerRequest> addRequestHeadersIfNotPresent(List<KeyValue> keyValues) {
+		HttpHeaders newHeaders = new HttpHeaders();
+		keyValues.forEach(keyValue -> newHeaders.add(keyValue.getKey(), keyValue.getValue()));
+		return request -> {
+			ServerRequest.Builder requestBuilder = ServerRequest.from(request);
+			newHeaders.forEach((newHeaderName, newHeaderValues) -> {
+				boolean headerIsMissingOrBlank = request.headers().asHttpHeaders().getOrEmpty(newHeaderName).stream()
+						.allMatch(h -> !StringUtils.hasText(h));
+				if (headerIsMissingOrBlank) {
+					requestBuilder.headers(httpHeaders -> {
+						List<String> expandedValues = MvcUtils.expandMultiple(request, newHeaderValues);
+						httpHeaders.addAll(newHeaderName, expandedValues);
+					});
+				}
+			});
+			return requestBuilder.build();
+		};
+	}
+
 	public static Function<ServerRequest, ServerRequest> addRequestParameter(String name, String... values) {
 		return request -> {
 			String[] expandedValues = MvcUtils.expandMultiple(request, values);

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

@@ -22,6 +22,7 @@ import java.util.Arrays;
 import java.util.Collection;
 
 import org.springframework.cloud.gateway.server.mvc.common.HttpStatusHolder;
+import org.springframework.cloud.gateway.server.mvc.common.KeyValues;
 import org.springframework.cloud.gateway.server.mvc.common.Shortcut;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatusCode;
@@ -40,6 +41,15 @@ public interface FilterFunctions {
 		return ofRequestProcessor(BeforeFilterFunctions.addRequestHeader(name, values));
 	}
 
+	static HandlerFilterFunction<ServerResponse, ServerResponse> addRequestHeadersIfNotPresent(String values) {
+		return addRequestHeadersIfNotPresent(KeyValues.valueOf(values));
+	}
+
+	@Shortcut
+	static HandlerFilterFunction<ServerResponse, ServerResponse> addRequestHeadersIfNotPresent(KeyValues keyValues) {
+		return ofRequestProcessor(BeforeFilterFunctions.addRequestHeadersIfNotPresent(keyValues.getKeyValues()));
+	}
+
 	@Shortcut
 	static HandlerFilterFunction<ServerResponse, ServerResponse> addRequestParameter(String name, String... values) {
 		return ofRequestProcessor(BeforeFilterFunctions.addRequestParameter(name, values));

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

@@ -84,6 +84,7 @@ import static org.springframework.cloud.gateway.server.mvc.filter.BeforeFilterFu
 import static org.springframework.cloud.gateway.server.mvc.filter.Bucket4jFilterFunctions.rateLimit;
 import static org.springframework.cloud.gateway.server.mvc.filter.CircuitBreakerFilterFunctions.circuitBreaker;
 import static org.springframework.cloud.gateway.server.mvc.filter.FilterFunctions.addRequestHeader;
+import static org.springframework.cloud.gateway.server.mvc.filter.FilterFunctions.addRequestHeadersIfNotPresent;
 import static org.springframework.cloud.gateway.server.mvc.filter.FilterFunctions.addRequestParameter;
 import static org.springframework.cloud.gateway.server.mvc.filter.FilterFunctions.prefixPath;
 import static org.springframework.cloud.gateway.server.mvc.filter.FilterFunctions.redirectTo;
@@ -475,6 +476,20 @@ public class ServerMvcIntegrationTests {
 				});
 	}
 
+	@Test
+	public void addRequestHeadersIfNotPresentWorks() {
+		restClient.get().uri("/headers").header("Host", "www.addrequestheadersifnotpresent.org")
+				.header("X-Request-Beta", "Value1").exchange().expectStatus().isOk().expectBody(Map.class)
+				.consumeWith(res -> {
+					Map<String, Object> headers = getMap(res.getResponseBody(), "headers");
+					// this asserts that Value2 was not added
+					assertThat(headers).containsEntry("X-Request-Beta", "Value1");
+					assertThat(headers).containsKey("X-Request-Acme");
+					List<String> values = (List<String>) headers.get("X-Request-Acme");
+					assertThat(values).hasSize(4).containsOnly("ValueX", "ValueY", "ValueZ", "www");
+				});
+	}
+
 	@SpringBootConfiguration
 	@EnableAutoConfiguration
 	@LoadBalancerClient(name = "httpbin", configuration = TestLoadBalancerConfig.Httpbin.class)
@@ -854,6 +869,18 @@ public class ServerMvcIntegrationTests {
 			// @formatter:on
 		}
 
+		@Bean
+		public RouterFunction<ServerResponse> gatewayRouterFunctionsAddRequestHeadersIfNotPresent() {
+			// @formatter:off
+			return route("testaddrequestheadersifnotpresent")
+					.route(GET("/headers").and(host("{sub}.addrequestheadersifnotpresent.org")), http())
+					.filter(new HttpbinUriResolver())
+					// normally use BeforeFilterFunctions version, but wanted to test parsing for config
+					.filter(addRequestHeadersIfNotPresent("X-Request-Acme:ValueX, X-Request-Acme:ValueY,X-Request-Acme:ValueZ, X-Request-Acme:{sub},X-Request-Beta:Value2"))
+					.build();
+			// @formatter:on
+		}
+
 	}
 
 	@RestController