Support reactive web servers with LocalServerPort

This commit refactors the `EmbeddedWebServerInitializedEvent` hierarchy
to have one specialized event for Servlet based apps and another one for
reactive apps.

Each event implementation has:

* a specific `ApplicationContext` implementation for the app
* a custom `getServerId` implementation that differentiates the
application server from the management server

Closes gh-8348

spring-boot/src/main/java/org/springframework/boot/context/embedded/EmbeddedReactiveWebServerInitializedEvent.java

+/*
+ * Copyright 2012-2017 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.boot.context.embedded;
+
+/**
+ * Event to be published after the {@link ReactiveWebApplicationContext} is
+ * refreshed and the {@link EmbeddedWebServer} is ready. Useful for
+ * obtaining the local port of a running server.
+ *
+ * @author Brian Clozel
+ * @author Stephane Nicoll
+ * @since 2.0.0
+ */
+public class EmbeddedReactiveWebServerInitializedEvent extends EmbeddedWebServerInitializedEvent {
+
+	private final ReactiveWebApplicationContext applicationContext;
+
+	public EmbeddedReactiveWebServerInitializedEvent(
+			EmbeddedWebServer source,
+			ReactiveWebApplicationContext applicationContext) {
+		super(source);
+		this.applicationContext = applicationContext;
+	}
+
+	@Override
+	public ReactiveWebApplicationContext getApplicationContext() {
+		return this.applicationContext;
+	}
+
+	@Override
+	public String getServerId() {
+		return "server";
+	}
+}

spring-boot/src/main/java/org/springframework/boot/context/embedded/EmbeddedServletContainerInitializedEvent.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.context.embedded;
 
+import org.springframework.util.StringUtils;
+
 /**
  * Event to be published after the {@link EmbeddedWebApplicationContext} is
  * refreshed and the {@link EmbeddedWebServer} is ready. Useful for
@@ -44,8 +46,18 @@ public class EmbeddedServletContainerInitializedEvent extends EmbeddedWebServerI
 	 * context) before acting on the server container itself.
 	 * @return the applicationContext that the container was created from
 	 */
+	@Override
 	public EmbeddedWebApplicationContext getApplicationContext() {
 		return this.applicationContext;
 	}
 
+	@Override
+	public String getServerId() {
+		String name = this.applicationContext.getNamespace();
+		if (StringUtils.isEmpty(name)) {
+			name = "server";
+		}
+		return name;
+	}
+
 }

spring-boot/src/main/java/org/springframework/boot/context/embedded/EmbeddedWebServerInitializedEvent.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.context.embedded;
 
+import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationEvent;
 
 /**
@@ -24,13 +25,15 @@ import org.springframework.context.ApplicationEvent;
  * obtaining the local port of a running server.
  *
  * @author Brian Clozel
+ * @author Stephane Nicoll
  * @since 2.0.0
  * @see EmbeddedServletContainerInitializedEvent
+ * @see EmbeddedReactiveWebServerInitializedEvent
  */
 @SuppressWarnings("serial")
-public class EmbeddedWebServerInitializedEvent extends ApplicationEvent {
+public abstract class EmbeddedWebServerInitializedEvent extends ApplicationEvent {
 
-	public EmbeddedWebServerInitializedEvent(EmbeddedWebServer source) {
+	protected EmbeddedWebServerInitializedEvent(EmbeddedWebServer source) {
 		super(source);
 	}
 
@@ -42,6 +45,14 @@ public class EmbeddedWebServerInitializedEvent extends ApplicationEvent {
 		return getSource();
 	}
 
+	/**
+	 * Access the application context that the container was created in. Sometimes it is
+	 * prudent to check that this matches expectations (like being equal to the current
+	 * context) before acting on the server container itself.
+	 * @return the applicationContext that the container was created from
+	 */
+	public abstract ApplicationContext getApplicationContext();
+
 	/**
 	 * Access the source of the event (an {@link EmbeddedWebServer}).
 	 * @return the embedded web server
@@ -50,4 +61,12 @@ public class EmbeddedWebServerInitializedEvent extends ApplicationEvent {
 	public EmbeddedWebServer getSource() {
 		return (EmbeddedWebServer) super.getSource();
 	}
+
+	/**
+	 * Access the {@link EmbeddedWebServer} Id used internally
+	 * to differentiate application / management servers.
+	 * @return the server internal Id
+	 */
+	public abstract String getServerId();
+
 }