Adds conifugration to allow http options globally.

This is done by adding a global cors config to simlple URL Handler mapping. Spring webflux adds a static resource handler, WebFluxAutoConfiguration.WebFluxConfig. This adds a SimpleURLHandler which will be the handler that ends returning http 404 for requets that match any spring cloud gateway predicates.

fixes gh-840

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

@@ -1556,6 +1556,8 @@ spring:
 
 In the example above, CORS requests will be allowed from requests that originate from docs.spring.io for all GET requested paths.
 
+To provide the same CORS configuration to requests that are not handled by some gateway route predicate, set the property `spring.cloud.gateway.globalcors.add-to-simple-url-handler-mapping` equal to true. This is useful when trying to support CORS preflight requests and your route predicate doesn't evalute to true because the http method is `options`.
+
 == Actuator API
 
 The `/gateway` actuator endpoint allows to monitor and interact with a Spring Cloud Gateway application. To be remotely accessible, the endpoint has to be https://docs.spring.io/spring-boot/docs/current/reference/html/production-ready-endpoints.html#production-ready-endpoints-enabling-endpoints[enabled] and https://docs.spring.io/spring-boot/docs/current/reference/html/production-ready-endpoints.html#production-ready-endpoints-exposing-endpoints[exposed via HTTP or JMX] in the application properties.

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

@@ -0,0 +1,50 @@
+/*
+ * 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
+ *
+ *      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.config;
+
+import javax.annotation.PostConstruct;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.reactive.handler.SimpleUrlHandlerMapping;
+
+/**
+ * This is useful for PreFlight CORS requests. We can add a "global" configuration here so
+ * we don't have to modify existing predicates to allow the "options" HTTP method.
+ *
+ */
+
+@Configuration
+@ConditionalOnClass(SimpleUrlHandlerMapping.class)
+@ConditionalOnProperty(name = "spring.cloud.gateway.globalcors.add-to-simple-url-handler-mapping", matchIfMissing = false)
+public class SimpleUrlHandlerMappingGlobalCorsAutoConfiguration {
+
+	@Autowired
+	private GlobalCorsProperties globalCorsProperties;
+
+	@Autowired
+	private SimpleUrlHandlerMapping simpleUrlHandlerMapping;
+
+	@PostConstruct
+	void config() {
+		simpleUrlHandlerMapping
+				.setCorsConfigurations(globalCorsProperties.getCorsConfigurations());
+	}
+
+}

spring-cloud-gateway-core/src/main/resources/META-INF/spring.factories

@@ -6,6 +6,8 @@ org.springframework.cloud.gateway.config.GatewayLoadBalancerClientAutoConfigurat
 org.springframework.cloud.gateway.config.GatewayNoLoadBalancerClientAutoConfiguration,\
 org.springframework.cloud.gateway.config.GatewayMetricsAutoConfiguration,\
 org.springframework.cloud.gateway.config.GatewayRedisAutoConfiguration,\
-org.springframework.cloud.gateway.discovery.GatewayDiscoveryClientAutoConfiguration
+org.springframework.cloud.gateway.discovery.GatewayDiscoveryClientAutoConfiguration,\
+org.springframework.cloud.gateway.config.SimpleUrlHandlerMappingGlobalCorsAutoConfiguration
+
 org.springframework.boot.env.EnvironmentPostProcessor=\
 org.springframework.cloud.gateway.config.GatewayEnvironmentPostProcessor

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

@@ -0,0 +1,92 @@
+/*
+ * 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
+ *
+ *      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.cors;
+
+import java.util.Arrays;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import reactor.core.publisher.Mono;
+
+import org.springframework.boot.SpringBootConfiguration;
+import org.springframework.boot.autoconfigure.AutoConfigureBefore;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.cloud.gateway.config.GatewayAutoConfiguration;
+import org.springframework.cloud.gateway.test.BaseWebClientTests;
+import org.springframework.context.annotation.Import;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.HttpStatus;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.ActiveProfiles;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.web.reactive.function.client.ClientResponse;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(webEnvironment = RANDOM_PORT, properties = "spring.cloud.gateway.globalcors.add-to-simple-url-handler-mapping=true")
+@DirtiesContext
+@ActiveProfiles("request-header-web-filter")
+public class SimpleUrlHandlerCorsTests extends BaseWebClientTests {
+
+	@Test
+	public void testPreFlightCorsRequestNotHandledByGW() {
+		ClientResponse clientResponse = webClient.options().uri("/abc/123/function")
+				.header("Origin", "domain.com")
+				.header("Access-Control-Request-Method", "GET").exchange().block();
+		HttpHeaders asHttpHeaders = clientResponse.headers().asHttpHeaders();
+		Mono<String> bodyToMono = clientResponse.bodyToMono(String.class);
+		// pre-flight request shouldn't return the response body
+		assertThat(bodyToMono.block()).isNull();
+		assertThat(asHttpHeaders.getAccessControlAllowOrigin())
+				.as("Missing header value in response: "
+						+ HttpHeaders.ACCESS_CONTROL_ALLOW_ORIGIN).isEqualTo("*");
+		assertThat(asHttpHeaders.getAccessControlAllowMethods())
+				.as("Missing header value in response: "
+						+ HttpHeaders.ACCESS_CONTROL_ALLOW_METHODS)
+				.isEqualTo(Arrays.asList(new HttpMethod[] {HttpMethod.GET}));
+		assertThat(clientResponse.statusCode()).as("Pre Flight call failed.")
+				.isEqualTo(HttpStatus.OK);
+	}
+
+	@Test
+	public void testCorsRequestNotHandledByGW() {
+		ClientResponse clientResponse = webClient.get().uri("/abc/123/function")
+				.header("Origin", "domain.com").header(HttpHeaders.HOST, "www.path.org")
+				.exchange().block();
+		HttpHeaders asHttpHeaders = clientResponse.headers().asHttpHeaders();
+		Mono<String> bodyToMono = clientResponse.bodyToMono(String.class);
+		assertThat(bodyToMono.block()).isNotNull();
+		assertThat(asHttpHeaders.getAccessControlAllowOrigin())
+				.as("Missing header value in response: "
+						+ HttpHeaders.ACCESS_CONTROL_ALLOW_ORIGIN).isEqualTo("*");
+		assertThat(clientResponse.statusCode()).as("CORS request failed.")
+				.isEqualTo(HttpStatus.NOT_FOUND);
+	}
+
+	@EnableAutoConfiguration
+	@SpringBootConfiguration
+	@AutoConfigureBefore(GatewayAutoConfiguration.class)
+	@Import(DefaultTestConfig.class)
+	public static class TestConfig {
+
+	}
+
+}