Disable child context's /error endpoint if disabled in parent

Previously, EndpointWebMvcChildContextConfiguration would attempt to
create a /error endpoint, irrespective of whether or not the parent
had such an endpoint. If the endpoint was disabled in the parent this
would cause a failure due to the absence of an ErrorAttributes bean.

This commit updates EndpointWebMvcChildContextConfiguration to make
the creation of its /error endpoint conditional on the existence of
an ErrorAttributes bean.

Closes gh-4164

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/autoconfigure/EndpointWebMvcChildContextConfiguration.java

@@ -75,9 +75,6 @@ public class EndpointWebMvcChildContextConfiguration {
 	@Value("${error.path:/error}")
 	private String errorPath = "/error";
 
-	@Autowired(required = false)
-	private List<EndpointHandlerMappingCustomizer> mappingCustomizers;
-
 	@Configuration
 	protected static class ServerCustomization
 			implements EmbeddedServletContainerCustomizer, Ordered {
@@ -144,11 +141,12 @@ public class EndpointWebMvcChildContextConfiguration {
 
 	/*
 	 * The error controller is present but not mapped as an endpoint in this context
-	 * because of the DispatcherServlet having had it's HandlerMapping explicitly
+	 * because of the DispatcherServlet having had its HandlerMapping explicitly disabled.
-	 * disabled. So we expose the same feature but only for machine endpoints.
+	 * So we expose the same feature but only for machine endpoints.
 	 */
 	@Bean
-	public ManagementErrorEndpoint errorEndpoint(final ErrorAttributes errorAttributes) {
+	@ConditionalOnBean(ErrorAttributes.class)
+	public ManagementErrorEndpoint errorEndpoint(ErrorAttributes errorAttributes) {
 		return new ManagementErrorEndpoint(this.errorPath, errorAttributes);
 	}
 

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/autoconfigure/EndpointWebMvcAutoConfigurationTests.java

@@ -27,6 +27,7 @@ import javax.servlet.ServletContext;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
+import org.hamcrest.Matcher;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
@@ -76,6 +77,7 @@ import static org.hamcrest.Matchers.instanceOf;
 import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.not;
 import static org.hamcrest.Matchers.notNullValue;
+import static org.hamcrest.Matchers.startsWith;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertThat;
@@ -146,6 +148,7 @@ public class EndpointWebMvcAutoConfigurationTests {
 		assertContent("/endpoint", ports.get().server, null);
 		assertContent("/controller", ports.get().management, null);
 		assertContent("/endpoint", ports.get().management, "endpointoutput");
+		assertContent("/error", ports.get().management, startsWith("{\"timestamp\""));
 		List<?> interceptors = (List<?>) ReflectionTestUtils.getField(
 				this.applicationContext.getBean(EndpointHandlerMapping.class),
 				"interceptors");
@@ -154,6 +157,17 @@ public class EndpointWebMvcAutoConfigurationTests {
 		assertAllClosed();
 	}
 
+	@Test
+	public void onDifferentPortWithoutErrorMvcAutoConfiguration() throws Exception {
+		this.applicationContext.register(RootConfig.class, EndpointConfig.class,
+				DifferentPortConfig.class, BaseConfiguration.class,
+				EndpointWebMvcAutoConfiguration.class);
+		this.applicationContext.refresh();
+		assertContent("/error", ports.get().management, null);
+		this.applicationContext.close();
+		assertAllClosed();
+	}
+
 	@Test
 	public void onDifferentPortInServletContainer() throws Exception {
 		this.applicationContext.register(RootConfig.class, EndpointConfig.class,
@@ -378,6 +392,7 @@ public class EndpointWebMvcAutoConfigurationTests {
 		assertContent("/endpoint", ports.get().management, null);
 	}
 
+	@SuppressWarnings("unchecked")
 	public void assertContent(String url, int port, Object expected) throws Exception {
 		SimpleClientHttpRequestFactory clientHttpRequestFactory = new SimpleClientHttpRequestFactory();
 		ClientHttpRequest request = clientHttpRequestFactory
@@ -387,8 +402,13 @@ public class EndpointWebMvcAutoConfigurationTests {
 			try {
 				String actual = StreamUtils.copyToString(response.getBody(),
 						Charset.forName("UTF-8"));
+				if (expected instanceof Matcher) {
+					assertThat(actual, is((Matcher<String>) expected));
+				}
+				else {
 					assertThat(actual, equalTo(expected));
 				}
+			}
 			finally {
 				response.close();
 			}