Adds event that will be fired before a service is registered. Fixes #302 (#424)

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

@@ -298,6 +298,15 @@ To disable that behavior, you can set:
 * `@EnableDiscoveryClient(autoRegister=false)` to permanently disable auto-registration.
 * `spring.cloud.service-registry.auto-registration.enabled=false` to disable the behavior through configuration.
 
+===== ServiceRegistry Auto-Registration Events
+
+There are two events that will be fired when a service auto-registers.  The first event, called
+`InstancePreRegisteredEvent`, is fired before the service is registered.  The second
+event, called `InstanceRegisteredEvent`, is fired after the service is registered.  You can register an
+`ApplicationListener`(s) to listen to and react to these events.
+
+NOTE: These events will not be fired if `spring.cloud.service-registry.auto-registration.enabled` is set to `false`.
+
 ==== Service Registry Actuator Endpoint
 
 Spring Cloud Commons provides a `/service-registry` actuator endpoint.

spring-cloud-commons/src/main/java/org/springframework/cloud/client/discovery/event/InstancePreRegisteredEvent.java

@@ -0,0 +1,47 @@
+/*
+ * 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.client.discovery.event;
+
+import org.springframework.cloud.client.serviceregistry.Registration;
+import org.springframework.context.ApplicationEvent;
+
+/**
+ * An event to fire before a service is registered.
+ * @author Ryan Baxter
+ */
+public class InstancePreRegisteredEvent extends ApplicationEvent {
+
+	private Registration registration;
+
+	/**
+	 * Create a new pre registration event.
+	 *
+	 * @param source the object on which the event initially occurred (never {@code null})
+	 */
+	public InstancePreRegisteredEvent(Object source, Registration registration) {
+		super(source);
+		this.registration = registration;
+	}
+
+	/**
+	 * Get the registration data.
+	 * @return the registration data
+	 */
+	public Registration getRegistration() {
+		return registration;
+	}
+}

spring-cloud-commons/src/main/java/org/springframework/cloud/client/serviceregistry/AbstractAutoServiceRegistration.java

@@ -6,6 +6,7 @@ import org.springframework.beans.BeansException;
 import org.springframework.boot.web.context.ConfigurableWebServerApplicationContext;
 import org.springframework.boot.web.context.WebServerInitializedEvent;
 import org.springframework.cloud.client.discovery.ManagementServerPortUtils;
+import org.springframework.cloud.client.discovery.event.InstancePreRegisteredEvent;
 import org.springframework.cloud.client.discovery.event.InstanceRegisteredEvent;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
@@ -105,6 +106,7 @@ public abstract class AbstractAutoServiceRegistration<R extends Registration>
 		// only initialize if nonSecurePort is greater than 0 and it isn't already running
 		// because of containerPortInitializer below
 		if (!this.running.get()) {
+			this.context.publishEvent(new InstancePreRegisteredEvent(this, getRegistration()));
 			register();
 			if (shouldRegisterManagement()) {
 				registerManagement();

spring-cloud-commons/src/test/java/org/springframework/cloud/client/serviceregistry/AbstractAutoServiceRegistrationTests.java

@@ -11,8 +11,12 @@ import org.springframework.boot.actuate.autoconfigure.web.server.LocalManagement
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.boot.web.server.LocalServerPort;
+import org.springframework.cloud.client.discovery.event.InstancePreRegisteredEvent;
+import org.springframework.cloud.client.discovery.event.InstanceRegisteredEvent;
+import org.springframework.context.ApplicationListener;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.stereotype.Component;
 import org.springframework.test.context.junit4.SpringRunner;
 
 import static org.hamcrest.Matchers.instanceOf;
@@ -34,6 +38,12 @@ public class AbstractAutoServiceRegistrationTests {
 	@Autowired
 	private TestAutoServiceRegistration autoRegistration;
 
+	@Autowired
+	private PreEventListener preEventListener;
+
+	@Autowired
+	public PostEventListener postEventListener;
+
 	@LocalServerPort
 	private int port;
 
@@ -52,6 +62,14 @@ public class AbstractAutoServiceRegistrationTests {
 		assertEquals("Lifecycle appName is wrong", "application", autoRegistration.getAppName());
 	}
 
+	@Test
+	public void eventsFireTest() {
+		assertTrue(preEventListener.wasFired);
+		assertEquals("testRegistration2", preEventListener.registration.getServiceId());
+		assertTrue(postEventListener.wasFired);
+		assertEquals("testRegistration2", postEventListener.config.getServiceId());
+	}
+
 	@EnableAutoConfiguration
 	@Configuration
 	public static class Config {
@@ -59,6 +77,36 @@ public class AbstractAutoServiceRegistrationTests {
 		public TestAutoServiceRegistration testAutoServiceRegistration() {
 			return new TestAutoServiceRegistration();
 		}
+
+		@Bean
+		public PreEventListener preRegisterListener() {
+			return new PreEventListener();
+		}
+
+		@Bean
+		public PostEventListener postEventListener() {
+			return new PostEventListener();
+		}
+	}
+
+	public static class PreEventListener implements ApplicationListener<InstancePreRegisteredEvent> {
+		public boolean wasFired = false;
+		public Registration registration;
+		@Override
+		public void onApplicationEvent(InstancePreRegisteredEvent event) {
+			this.registration = event.getRegistration();
+			this.wasFired = true;
+		}
+	}
+
+	public static class PostEventListener implements ApplicationListener<InstanceRegisteredEvent> {
+		public boolean wasFired = false;
+		public Registration config;
+		@Override
+		public void onApplicationEvent(InstanceRegisteredEvent event) {
+			this.config = (Registration)event.getConfig();
+			this.wasFired = true;
+		}
 	}
 
 	public static class TestRegistration implements Registration {
@@ -188,7 +236,7 @@ public class AbstractAutoServiceRegistrationTests {
 
 		@Override
 		protected Object getConfiguration() {
-			return null;
+			return getRegistration();
 		}
 
 		@Override