Strip Prefix Filter Implementation (#180)

* Implements a filter to strip the prefix from a request through the gateway.  Fixes #122

* The number of parts to strip is now configurable

* Updated documentation

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

@@ -616,6 +616,26 @@ spring:
 
 In either case, the HTTP status of the response will be set to 401.
 
+=== StripPrefix GatewayFilter Factory
+The StripPrefix GatewayFilter Factory takes one paramter, `parts`.  The `parts` parameter indicated the number of parts in the path to strip from the request before sending it downstream.
+
+.application.yml
+[source,yaml]
+----
+spring:
+  cloud:
+    gateway:
+      routes:
+      - id: nameRoot
+        uri: http://nameservice
+        predicates:
+        - Path=/name/**
+        filters:
+        - StripPrefix=2
+----
+
+When a request is made through the gateway to `/name/bar/foo` the request made to `nameservice` will look like `http://nameservice/foo`.
+
 == Global Filters
 
 The `GlobalFilter` interface has the same signature as `GatewayFilter`. These are special filters that are conditionally applied to all routes. (This interface and usage are subject to change in future milestones).

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

@@ -61,6 +61,7 @@ import org.springframework.cloud.gateway.filter.factory.SetPathGatewayFilterFact
 import org.springframework.cloud.gateway.filter.factory.SetRequestHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SetResponseHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SetStatusGatewayFilterFactory;
+import org.springframework.cloud.gateway.filter.factory.StripPrefixGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.ratelimit.KeyResolver;
 import org.springframework.cloud.gateway.filter.ratelimit.PrincipalNameKeyResolver;
 import org.springframework.cloud.gateway.filter.ratelimit.RateLimiter;
@@ -409,6 +410,11 @@ public class GatewayAutoConfiguration {
 		return new SaveSessionGatewayFilterFactory();
 	}
 
+	@Bean
+	public StripPrefixGatewayFilterFactory stripPrefixGatewayFilterFactory() {
+		return new StripPrefixGatewayFilterFactory();
+	}
+
 	@Configuration
 	@ConditionalOnClass(Health.class)
 	protected static class GatewayActuatorConfiguration {

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

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2013-2018 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
+ *
+ *      http://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.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+import org.springframework.cloud.gateway.filter.GatewayFilter;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+import org.springframework.tuple.Tuple;
+import org.springframework.util.StringUtils;
+
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR;
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.addOriginalRequestUrl;
+
+/**
+ * This filter removes the first part of the path, known as the prefix, from the request
+ * before sending it downstream
+ * @author Ryan Baxter
+ */
+public class StripPrefixGatewayFilterFactory implements GatewayFilterFactory {
+
+	public static final String PARTS_KEY = "parts";
+
+	@Override
+	public List<String> argNames() {
+		return Arrays.asList(PARTS_KEY);
+	}
+
+	@Override
+	public GatewayFilter apply(Tuple args) {
+		final int parts = args.getInt(PARTS_KEY);
+		return apply(parts);
+	}
+
+	public GatewayFilter apply(int parts) {
+		return (exchange, chain) ->  {
+			ServerHttpRequest request = exchange.getRequest();
+			addOriginalRequestUrl(exchange, request.getURI());
+			String path = request.getURI().getRawPath();
+			String newPath = "/" + Arrays.stream(StringUtils.tokenizeToStringArray(path, "/"))
+					.skip(parts).collect(Collectors.joining("/"));
+			ServerHttpRequest newRequest = request.mutate()
+					.path(newPath)
+					.build();
+
+			exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, newRequest.getURI());
+
+			return chain.filter(exchange.mutate().request(newRequest).build());
+		};
+	}
+}

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

@@ -45,6 +45,7 @@ import org.springframework.cloud.gateway.filter.factory.SetPathGatewayFilterFact
 import org.springframework.cloud.gateway.filter.factory.SetRequestHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SetResponseHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SetStatusGatewayFilterFactory;
+import org.springframework.cloud.gateway.filter.factory.StripPrefixGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.ratelimit.KeyResolver;
 import org.springframework.cloud.gateway.route.Route;
 import org.springframework.core.Ordered;
@@ -232,4 +233,8 @@ public class GatewayFilterSpec extends UriSpec {
 	public GatewayFilterSpec saveSession() {
 		return filter(getBean(SaveSessionGatewayFilterFactory.class).apply(EMPTY_TUPLE));
 	}
+
+	public GatewayFilterSpec stripPrefix(int parts) {
+		return filter(getBean(StripPrefixGatewayFilterFactory.class).apply(parts));
+	}
 }

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

@@ -0,0 +1,84 @@
+/*
+ * Copyright 2013-2018 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
+ *
+ *      http://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 reactor.core.publisher.Mono;
+
+import java.net.URI;
+import java.util.LinkedHashSet;
+
+import org.junit.Test;
+import org.mockito.ArgumentCaptor;
+import org.springframework.cloud.gateway.filter.GatewayFilter;
+import org.springframework.cloud.gateway.filter.GatewayFilterChain;
+import org.springframework.mock.http.server.reactive.MockServerHttpRequest;
+import org.springframework.mock.web.server.MockServerWebExchange;
+import org.springframework.web.server.ServerWebExchange;
+
+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.support.ServerWebExchangeUtils.GATEWAY_ORIGINAL_REQUEST_URL_ATTR;
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR;
+import static org.springframework.tuple.TupleBuilder.tuple;
+
+/**
+ * @author Ryan Baxter
+ */
+public class StripPrefixGatewayFilterFactoryTest {
+
+	@Test
+	public void testStripPrefix() throws Exception {
+		testStripPrefixFilter("/foo/bar", "/bar", 1);
+		testStripPrefixFilter("/foo/bar", "/", 2);
+		testStripPrefixFilter("/foo/bar", "/foo/bar", 0);
+		testStripPrefixFilter("", "/", 1);
+		testStripPrefixFilter("/", "/", 1);
+		testStripPrefixFilter("/", "/", 2);
+		testStripPrefixFilter("", "/", 2);
+		testStripPrefixFilter("/this/is/a/long/path/with/a/lot/of/slashes", "/path/with/a/lot/of/slashes", 4);
+	}
+
+
+	private void testStripPrefixFilter(String actualPath, String expectedPath, int parts) {
+		GatewayFilter filter = new StripPrefixGatewayFilterFactory().apply(
+				tuple().of(StripPrefixGatewayFilterFactory.PARTS_KEY, parts));
+
+		MockServerHttpRequest request = MockServerHttpRequest
+				.get("http://localhost"+ actualPath)
+				.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();
+
+		assertThat(webExchange.getRequest().getURI()).hasPath(expectedPath);
+
+		URI requestUrl = webExchange.getRequiredAttribute(GATEWAY_REQUEST_URL_ATTR);
+		assertThat(requestUrl).hasScheme("http").hasHost("localhost").hasNoPort().hasPath(expectedPath);
+		LinkedHashSet<URI> uris = webExchange.getRequiredAttribute(GATEWAY_ORIGINAL_REQUEST_URL_ATTR);
+		assertThat(uris).contains(request.getURI());
+	}
+
+}

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

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2013-2018 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
+ *
+ *      http://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 reactor.core.publisher.Mono;
+import reactor.test.StepVerifier;
+
+import org.junit.Test;
+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.test.BaseWebClientTests;
+import org.springframework.context.annotation.Import;
+import org.springframework.http.HttpStatus;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.web.reactive.function.client.ClientResponse;
+
+import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;
+import static org.springframework.cloud.gateway.test.TestUtils.assertStatus;
+
+/**
+ * @author Ryan Baxter
+ */
+@RunWith(SpringRunner.class)
+@SpringBootTest(webEnvironment = RANDOM_PORT)
+@DirtiesContext
+public class StripPrefixGatewayFilterFactoryTestIntegrationTests extends BaseWebClientTests {
+
+	@Test
+	public void stripPrefixFilterDefaultValuesWork() {
+		Mono<ClientResponse> result = webClient.get()
+				.uri("/foo/bar/get")
+				.header("Host", "www.stripprefix.org")
+				.exchange();
+
+		StepVerifier.create(result)
+				.consumeNextWith(
+						response -> {
+							assertStatus(response, HttpStatus.OK);
+						})
+				.expectComplete()
+				.verify(DURATION);
+	}
+
+	@EnableAutoConfiguration
+	@SpringBootConfiguration
+	@Import(BaseWebClientTests.DefaultTestConfig.class)
+	public static class TestConfig { }
+
+}

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

@@ -149,6 +149,15 @@ spring:
         filters:
         - SetPath=/{segment}
 
+      # =====================================
+      - id: strip_prefix_test
+        uri: ${test.uri}
+        predicates:
+        - Host=**.stripprefix.org
+        - Path=/foo/**
+        filters:
+        - StripPrefix=2
+
       # =====================================
       - id: set_response_header_test
         uri: ${test.uri}