Allow Jersey-based Actuator to be used with separate management port

Previously, when the Jersey-based Actuator was configure with a
separate management port, the resulting child context would fail to
start due to their being no ResourceConfigCustomizer beans available.

This commit updates the configuration so that the customizer's are
injected using an ObjectProvider and an empty list is used in the
event of their being no customizer beans. This aligns the child
context configuration class with JerseyAutoConfiguration which
already used this approach.

Closes gh-12975

Author: wilkinsona

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/web/jersey/JerseyManagementChildContextConfiguration.java

@@ -16,11 +16,13 @@
 
 package org.springframework.boot.actuate.autoconfigure.web.jersey;
 
+import java.util.Collections;
 import java.util.List;
 
 import org.glassfish.jersey.server.ResourceConfig;
 import org.glassfish.jersey.servlet.ServletContainer;
 
+import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.boot.actuate.autoconfigure.web.ManagementContextConfiguration;
 import org.springframework.boot.actuate.autoconfigure.web.ManagementContextType;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
@@ -49,8 +51,9 @@ public class JerseyManagementChildContextConfiguration {
 	private final List<ResourceConfigCustomizer> resourceConfigCustomizers;
 
 	public JerseyManagementChildContextConfiguration(
-			List<ResourceConfigCustomizer> resourceConfigCustomizers) {
-		this.resourceConfigCustomizers = resourceConfigCustomizers;
+			ObjectProvider<List<ResourceConfigCustomizer>> resourceConfigCustomizers) {
+		this.resourceConfigCustomizers = resourceConfigCustomizers
+				.getIfAvailable(Collections::emptyList);
 	}
 
 	@Bean

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/web/jersey/JerseyManagementChildContextConfigurationTests.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2012-2018 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.boot.actuate.autoconfigure.web.jersey;
+
+import org.glassfish.jersey.server.ResourceConfig;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.boot.autoconfigure.jersey.ResourceConfigCustomizer;
+import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
+import org.springframework.boot.testsupport.runner.classpath.ClassPathExclusions;
+import org.springframework.boot.testsupport.runner.classpath.ModifiedClassPathRunner;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+/**
+ * Tests for {@link JerseyManagementChildContextConfiguration}.
+ *
+ * @author Andy Wilkinson
+ */
+@RunWith(ModifiedClassPathRunner.class)
+@ClassPathExclusions("spring-webmvc-*")
+public class JerseyManagementChildContextConfigurationTests {
+
+	private final WebApplicationContextRunner contextRunner = new WebApplicationContextRunner()
+			.withUserConfiguration(JerseyManagementChildContextConfiguration.class);
+
+	@Test
+	public void resourceConfigIsCustomizedWithResourceConfigCustomizerBean() {
+		this.contextRunner.withUserConfiguration(CustomizerConfiguration.class)
+				.run((context) -> {
+					assertThat(context).hasSingleBean(ResourceConfig.class);
+					ResourceConfig config = context.getBean(ResourceConfig.class);
+					ResourceConfigCustomizer customizer = context
+							.getBean(ResourceConfigCustomizer.class);
+					verify(customizer).customize(config);
+				});
+	}
+
+	@Test
+	public void resourceConfigCustomizerBeanIsNotRequired() {
+		this.contextRunner.run(
+				(context) -> assertThat(context).hasSingleBean(ResourceConfig.class));
+	}
+
+	@Configuration
+	static class CustomizerConfiguration {
+
+		@Bean
+		ResourceConfigCustomizer resourceConfigCustomizer() {
+			return mock(ResourceConfigCustomizer.class);
+		}
+
+	}
+
+}