Add support for forward:/// uri's.

Let's spring's `DispatcherHandler` handle forwarded requests.

fixes gh-78

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

@@ -582,9 +582,17 @@ In either case, the HTTP status of the response will be set to 401.
 
 The `GlobalFilter` interface has the same signature as `WebFilter`. These are special filters that are conditionally applied to all routes. (This interface and usage are subject to change in future milestones).
 
+=== Combined Global Filter and WebFilter Ordering
+
+TODO: document ordering
+
+=== Forward Routing Filter
+
+The `ForwardRoutingFilter` looks for a URI in the exchange attribute `ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR`. If the url has a `forward` scheme (ie `forward:///localendpoint`), it will use the Spring `DispatcherHandler` to handler the request. The unmodified original url is appended to the list in the `ServerWebExchangeUtils.GATEWAY_ORIGINAL_REQUEST_URL_ATTR` attribute.
+
 === LoadBalancerClient Filter
 
-The `LoadBalancerClientFilter` looks for a URI in the exchange attribute `ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR`. If the url has a `lb` scheme (ie `lb://myservice`), it will use the Spring Cloud `LoadBalancerClient` to resolve the name (`myservice` in the previous example) to an actual host and port and replace the URI in the same attribute. The unmodified original url is placed in the `ServerWebExchangeUtils.GATEWAY_ORIGINAL_REQUEST_URL_ATTR` attribute.
+The `LoadBalancerClientFilter` looks for a URI in the exchange attribute `ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR`. If the url has a `lb` scheme (ie `lb://myservice`), it will use the Spring Cloud `LoadBalancerClient` to resolve the name (`myservice` in the previous example) to an actual host and port and replace the URI in the same attribute. The unmodified original url is appended to the list in the `ServerWebExchangeUtils.GATEWAY_ORIGINAL_REQUEST_URL_ATTR` attribute.
 
 === Netty Routing Filter
 

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

@@ -31,6 +31,7 @@ import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.boot.autoconfigure.web.reactive.HttpHandlerAutoConfiguration;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.cloud.gateway.actuate.GatewayEndpoint;
+import org.springframework.cloud.gateway.filter.ForwardRoutingFilter;
 import org.springframework.cloud.gateway.filter.GlobalFilter;
 import org.springframework.cloud.gateway.filter.NettyRoutingFilter;
 import org.springframework.cloud.gateway.filter.NettyWriteResponseFilter;
@@ -81,6 +82,7 @@ import org.springframework.cloud.gateway.route.RouteLocator;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Primary;
+import org.springframework.web.reactive.DispatcherHandler;
 import org.springframework.web.reactive.socket.client.ReactorNettyWebSocketClient;
 import org.springframework.web.reactive.socket.client.WebSocketClient;
 import org.springframework.web.reactive.socket.server.WebSocketService;
@@ -199,6 +201,12 @@ public class GatewayAutoConfiguration {
 		return new RouteToRequestUrlFilter();
 	}
 
+	@Bean
+	@ConditionalOnBean(DispatcherHandler.class)
+	public ForwardRoutingFilter forwardRoutingFilter(DispatcherHandler dispatcherHandler) {
+		return new ForwardRoutingFilter(dispatcherHandler);
+	}
+
 	@Bean
 	public WebSocketService webSocketService() {
 		return new HandshakeWebSocketService();

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

@@ -0,0 +1,50 @@
+package org.springframework.cloud.gateway.filter;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.springframework.core.Ordered;
+import org.springframework.web.reactive.DispatcherHandler;
+import org.springframework.web.server.ServerWebExchange;
+import org.springframework.web.server.WebFilterChain;
+import reactor.core.publisher.Mono;
+
+import java.net.URI;
+
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR;
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.isAlreadyRouted;
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.setAlreadyRouted;
+
+public class ForwardRoutingFilter implements GlobalFilter, Ordered {
+
+	private static final Log log = LogFactory.getLog(ForwardRoutingFilter.class);
+
+	private final DispatcherHandler dispatcherHandler;
+
+	public ForwardRoutingFilter(DispatcherHandler dispatcherHandler) {
+		this.dispatcherHandler = dispatcherHandler;
+	}
+
+	@Override
+	public int getOrder() {
+		return Ordered.LOWEST_PRECEDENCE;
+	}
+
+	@Override
+	public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {
+		URI requestUrl = exchange.getRequiredAttribute(GATEWAY_REQUEST_URL_ATTR);
+
+		String scheme = requestUrl.getScheme();
+		if (isAlreadyRouted(exchange) || !scheme.equals("forward")) {
+			return chain.filter(exchange);
+		}
+		setAlreadyRouted(exchange);
+
+		//TODO: translate url?
+
+		if (log.isTraceEnabled()) {
+			log.trace("Forwarding to URI: "+requestUrl);
+		}
+
+		return this.dispatcherHandler.handle(exchange);
+	}
+}

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

@@ -17,18 +17,25 @@
 
 package org.springframework.cloud.gateway.filter.factory;
 
+import java.util.Arrays;
+import java.util.List;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.tuple.Tuple;
 import org.springframework.web.server.WebFilter;
 
-import java.util.Arrays;
-import java.util.List;
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR;
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.addOriginalRequestUrl;
 
 /**
  * @author Spencer Gibb
  */
 public class PrefixPathWebFilterFactory implements WebFilterFactory {
 
+	private static final Log log = LogFactory.getLog(PrefixPathWebFilterFactory.class);
+
 	public static final String PREFIX_KEY = "prefix";
 
 	@Override
@@ -43,12 +50,19 @@ public class PrefixPathWebFilterFactory implements WebFilterFactory {
 
 		return (exchange, chain) -> {
 			ServerHttpRequest req = exchange.getRequest();
+			addOriginalRequestUrl(exchange, req.getURI());
 			String newPath = prefix + req.getURI().getPath();
 
 			ServerHttpRequest request = req.mutate()
 					.path(newPath)
 					.build();
 
+			exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, request.getURI());
+
+			if (log.isTraceEnabled()) {
+				log.trace("Prefixed URI with: "+prefix+" -> "+request.getURI());
+			}
+
 			return chain.filter(exchange.mutate().request(request).build());
 		};
 	}

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

@@ -29,6 +29,7 @@ import org.springframework.web.server.WebFilter;
 import org.springframework.web.util.UriTemplate;
 import org.springframework.web.util.pattern.PathPattern.PathMatchInfo;
 
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR;
 import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.URI_TEMPLATE_VARIABLES_ATTRIBUTE;
 import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.addOriginalRequestUrl;
 
@@ -66,6 +67,8 @@ public class SetPathWebFilterFactory implements WebFilterFactory {
 			URI uri = uriTemplate.expand(uriVariables);
 			String newPath = uri.getPath();
 
+			exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, uri);
+
 			ServerHttpRequest request = req.mutate()
 					.path(newPath)
 					.build();

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/support/ServerWebExchangeUtils.java

@@ -37,7 +37,7 @@ public class ServerWebExchangeUtils {
 	public static final String CLIENT_RESPONSE_ATTR = qualify("webHandlerClientResponse");
 	public static final String GATEWAY_ROUTE_ATTR = qualify("gatewayRoute");
 	public static final String GATEWAY_REQUEST_URL_ATTR = qualify("gatewayRequestUrl");
-	public static final String GATEWAY_ORIGINAL_REQUEST_URL_ATTR = qualify("gatewayOribinalRequestUrl");
+	public static final String GATEWAY_ORIGINAL_REQUEST_URL_ATTR = qualify("gatewayOriginalRequestUrl");
 	public static final String GATEWAY_HANDLER_MAPPER_ATTR = qualify("gatewayHandlerMapper");
 
 	/**

spring-cloud-gateway-core/src/test/java/org/springframework/cloud/gateway/test/ForwardTests.java

@@ -0,0 +1,81 @@
+/*
+ * Copyright 2013-2017 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.test;
+
+import org.junit.Before;
+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.boot.web.server.LocalServerPort;
+import org.springframework.context.annotation.Import;
+import org.springframework.http.HttpHeaders;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.test.web.reactive.server.WebTestClient;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.Collections;
+import java.util.Map;
+
+import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(webEnvironment = RANDOM_PORT)
+@DirtiesContext
+@SuppressWarnings("unchecked")
+public class ForwardTests {
+	@LocalServerPort
+	protected int port = 0;
+
+	protected WebTestClient client;
+
+	@Before
+	public void setup() {
+		String baseUri = "http://localhost:" + port;
+		this.client = WebTestClient.bindToServer()
+				.baseUrl(baseUri)
+				.build();
+	}
+
+	@Test
+	public void forwardWorks() {
+		this.client
+				.get()
+				.uri("/localcontroller")
+				.header(HttpHeaders.HOST, "www.forward.org")
+				.exchange()
+				.expectStatus().isOk()
+				.expectBody().json("{\"from\":\"localcontroller\"}");
+	}
+
+	@EnableAutoConfiguration
+	@SpringBootConfiguration
+	@RestController
+	@Import(PermitAllSecurityConfiguration.class)
+	public static class TestConfig {
+
+		@RequestMapping("/httpbin/localcontroller")
+		public Map<String, String> localController() {
+			return Collections.singletonMap("from", "localcontroller");
+		}
+	}
+
+}

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

@@ -58,6 +58,12 @@ spring:
         filters:
         - AddResponseHeader=X-Request-Foo, Bar
 
+      # =====================================
+      - id: forward_test
+        uri: forward:///localcontroller
+        predicates:
+        - Host=**.forward.org
+
       # =====================================
       - id: hystrix_failure_test
         uri: ${test.uri}