Activate DiscoveryClient integration with a property

fixes gh-123

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

@@ -681,6 +681,12 @@ public RouteLocator customRouteLocator(ThrottleGatewayFilterFactory throttle) {
 
 This style also allows for more custom predicate assertions. The predicates defined by `RouteDefinitionLocator` beans are combined using logical `and`. By using the fluent Java API, you can use the `and()`, `or()` and `negate()` operators on the `Predicate` class.
 
+=== DiscoveryClient Route Definition Locator
+
+The Gateway can be configured to create routes based on services registered with a `DiscoveryClient` compatible service registry.
+
+To enable this, set `spring.cloud.gateway.discovery.locator.enabled=true` and make sure a `DiscoveryClient` implementation is on the classpath and enabled (such as Netflix Eureka, Consul or Zookeeper).
+
 == Actuator API
 
 TODO: document the `/gateway` actuator endpoint

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/discovery/GatewayDiscoveryClientAutoConfiguration.java

@@ -0,0 +1,46 @@
+/*
+ * 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.discovery;
+
+import org.springframework.boot.autoconfigure.AutoConfigureBefore;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.cloud.client.discovery.DiscoveryClient;
+import org.springframework.cloud.gateway.config.GatewayAutoConfiguration;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.reactive.DispatcherHandler;
+
+/**
+ * @author Spencer Gibb
+ */
+@Configuration
+@ConditionalOnProperty(name = "spring.cloud.gateway.enabled", matchIfMissing = true)
+@AutoConfigureBefore(GatewayAutoConfiguration.class)
+@ConditionalOnClass({DispatcherHandler.class, DiscoveryClient.class})
+public class GatewayDiscoveryClientAutoConfiguration {
+
+	@Bean
+	@ConditionalOnBean(DiscoveryClient.class)
+	@ConditionalOnProperty(name = "spring.cloud.gateway.discovery.locator.enabled")
+	public DiscoveryClientRouteDefinitionLocator discoveryClientRouteDefinitionLocator(DiscoveryClient discoveryClient) {
+		return new DiscoveryClientRouteDefinitionLocator(discoveryClient);
+	}
+
+}
+

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

@@ -3,4 +3,5 @@ org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
 org.springframework.cloud.gateway.config.GatewayClassPathWarningAutoConfiguration,\
 org.springframework.cloud.gateway.config.GatewayAutoConfiguration,\
 org.springframework.cloud.gateway.config.GatewayLoadBalancerClientAutoConfiguration,\
-org.springframework.cloud.gateway.config.GatewayRedisAutoConfiguration
+org.springframework.cloud.gateway.config.GatewayRedisAutoConfiguration,\
+org.springframework.cloud.gateway.discovery.GatewayDiscoveryClientAutoConfiguration

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

@@ -0,0 +1,76 @@
+/*
+ * 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.discovery;
+
+import org.junit.Test;
+import org.junit.experimental.runners.Enclosed;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.SpringBootConfiguration;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.cloud.client.discovery.DiscoveryClient;
+import org.springframework.context.annotation.Bean;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+
+@RunWith(Enclosed.class)
+public class GatewayDiscoveryClientAutoConfigurationTests {
+
+	@RunWith(SpringRunner.class)
+	@SpringBootTest(classes = Config.class,
+			properties = "spring.cloud.gateway.discovery.locator.enabled=true")
+	public static class EnabledByProperty {
+
+		@Autowired(required = false)
+		private DiscoveryClientRouteDefinitionLocator locator;
+
+		@Test
+		public void routeLocatorBeanExists() {
+			assertThat(locator)
+					.as("DiscoveryClientRouteDefinitionLocator was null")
+					.isNotNull();
+		}
+	}
+
+	@RunWith(SpringRunner.class)
+	@SpringBootTest(classes = Config.class)
+	public static class DisabledByDefault {
+		@Autowired(required = false)
+		private DiscoveryClientRouteDefinitionLocator locator;
+
+		@Test
+		public void routeLocatorBeanMissing() {
+			assertThat(locator)
+					.as("DiscoveryClientRouteDefinitionLocator exists")
+					.isNull();
+		}
+	}
+
+
+	@SpringBootConfiguration
+	@EnableAutoConfiguration
+	protected static class Config {
+
+		@Bean
+		DiscoveryClient discoveryClient() {
+			return mock(DiscoveryClient.class);
+		}
+	}
+}