Fail if management.server.address is set but actuator is on the same port

Closes gh-22187

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/web/server/ManagementContextAutoConfiguration.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -73,6 +73,7 @@ public class ManagementContextAutoConfiguration {
 		@Override
 		public void afterSingletonsInstantiated() {
 			verifySslConfiguration();
+			verifyAddressConfiguration();
 			if (this.environment instanceof ConfigurableEnvironment) {
 				addLocalManagementPortPropertyAlias((ConfigurableEnvironment) this.environment);
 			}
@@ -84,6 +85,12 @@ public class ManagementContextAutoConfiguration {
 					+ "server is not listening on a separate port");
 		}
 
+		private void verifyAddressConfiguration() {
+			Object address = this.environment.getProperty("management.server.address");
+			Assert.state(address == null, "Management-specific server address cannot be configured as the management "
+					+ "server is not listening on a separate port");
+		}
+
 		/**
 		 * Add an alias for 'local.management.port' that actually resolves using
 		 * 'local.server.port'.

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/web/server/ManagementContextAutoConfigurationTests.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -24,6 +24,7 @@ import org.springframework.boot.actuate.autoconfigure.endpoint.EndpointAutoConfi
 import org.springframework.boot.actuate.autoconfigure.endpoint.web.WebEndpointAutoConfiguration;
 import org.springframework.boot.actuate.autoconfigure.web.servlet.ServletManagementContextAutoConfiguration;
 import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration;
 import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
 import org.springframework.boot.test.system.CapturedOutput;
@@ -54,6 +55,19 @@ class ManagementContextAutoConfigurationTests {
 				.run((context) -> assertThat(output).satisfies(numberOfOccurrences("Tomcat started on port", 2)));
 	}
 
+	@Test
+	void givenSamePortManagementServerWhenManagementServerAddressIsConfiguredThenContextRefreshFails() {
+		WebApplicationContextRunner contextRunner = new WebApplicationContextRunner(
+				AnnotationConfigServletWebServerApplicationContext::new)
+						.withConfiguration(AutoConfigurations.of(ManagementContextAutoConfiguration.class,
+								ServletWebServerFactoryAutoConfiguration.class,
+								ServletManagementContextAutoConfiguration.class, WebEndpointAutoConfiguration.class,
+								EndpointAutoConfiguration.class, DispatcherServletAutoConfiguration.class));
+		contextRunner.withPropertyValues("server.port=0", "management.server.address=127.0.0.1")
+				.run((context) -> assertThat(context).getFailure()
+						.hasMessageStartingWith("Management-specific server address cannot be configured"));
+	}
+
 	private <T extends CharSequence> Consumer<T> numberOfOccurrences(String substring, int expectedCount) {
 		return (charSequence) -> {
 			int count = StringUtils.countOccurrencesOf(charSequence.toString(), substring);