Add CORS interceptor for Cloud Foundry actuators

This interceptor processes the response with CORS headers
and apepars before the Cloud Foundry security interceptor.

See gh-7108

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/cloudfoundry/CloudFoundryEndpointHandlerMapping.java

@@ -23,6 +23,7 @@ import java.util.List;
 import java.util.Set;
 
 import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
 
 import org.springframework.boot.actuate.endpoint.Endpoint;
 import org.springframework.boot.actuate.endpoint.mvc.AbstractEndpointHandlerMapping;
@@ -34,6 +35,7 @@ import org.springframework.web.cors.CorsConfiguration;
 import org.springframework.web.servlet.HandlerExecutionChain;
 import org.springframework.web.servlet.HandlerInterceptor;
 import org.springframework.web.servlet.HandlerMapping;
+import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;
 
 /**
  * {@link HandlerMapping} to map {@link Endpoint}s to Cloud Foundry specific URLs.
@@ -45,10 +47,13 @@ class CloudFoundryEndpointHandlerMapping
 
 	private final HandlerInterceptor securityInterceptor;
 
+	private final CorsConfiguration corsConfiguration;
+
 	CloudFoundryEndpointHandlerMapping(Set<? extends NamedMvcEndpoint> endpoints,
 			CorsConfiguration corsConfiguration, HandlerInterceptor securityInterceptor) {
 		super(endpoints, corsConfiguration);
 		this.securityInterceptor = securityInterceptor;
+		this.corsConfiguration = corsConfiguration;
 	}
 
 	@Override
@@ -97,6 +102,7 @@ class CloudFoundryEndpointHandlerMapping
 
 	private HandlerInterceptor[] addSecurityInterceptor(HandlerInterceptor[] existing) {
 		List<HandlerInterceptor> interceptors = new ArrayList<HandlerInterceptor>();
+		interceptors.add(new CorsInterceptor(this.corsConfiguration));
 		interceptors.add(this.securityInterceptor);
 		if (existing != null) {
 			interceptors.addAll(Arrays.asList(existing));
@@ -104,4 +110,23 @@ class CloudFoundryEndpointHandlerMapping
 		return interceptors.toArray(new HandlerInterceptor[interceptors.size()]);
 	}
 
+	/**
+	 * {@link HandlerInterceptor} that processes the response for CORS.
+	 *
+	 */
+	class CorsInterceptor extends HandlerInterceptorAdapter {
+		private final CorsConfiguration config;
+
+		CorsInterceptor(CorsConfiguration config) {
+			this.config = config;
+		}
+
+		@Override
+		public boolean preHandle(HttpServletRequest request, HttpServletResponse response,
+				Object handler) throws Exception {
+			return getCorsProcessor().processRequest(this.config, request, response);
+		}
+
+	}
+
 }

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/cloudfoundry/CloudFoundryEndpointHandlerMappingTests.java

@@ -33,6 +33,9 @@ import org.springframework.boot.actuate.health.HealthIndicator;
 import org.springframework.boot.actuate.health.OrderedHealthAggregator;
 import org.springframework.context.support.StaticApplicationContext;
 import org.springframework.mock.web.MockHttpServletRequest;
+import org.springframework.mock.web.MockHttpServletResponse;
+import org.springframework.web.cors.CorsConfiguration;
+import org.springframework.web.cors.CorsProcessor;
 import org.springframework.web.method.HandlerMethod;
 import org.springframework.web.servlet.HandlerExecutionChain;
 import org.springframework.web.servlet.HandlerInterceptor;
@@ -47,6 +50,25 @@ import static org.assertj.core.api.Assertions.assertThat;
 public class CloudFoundryEndpointHandlerMappingTests
 		extends AbstractEndpointHandlerMappingTests {
 
+	@Test
+	public void corsInterceptorShouldBeFirstAndCallCorsProcessor() throws Exception {
+		TestMvcEndpoint endpoint = new TestMvcEndpoint(new TestEndpoint("a"));
+		CorsConfiguration corsConfiguration = new CorsConfiguration();
+		CloudFoundryEndpointHandlerMapping handlerMapping = new CloudFoundryEndpointHandlerMapping(
+				Collections.singleton(endpoint), corsConfiguration, null);
+		CorsProcessor corsProcessor = Mockito.mock(CorsProcessor.class);
+		handlerMapping.setCorsProcessor(corsProcessor);
+		MockHttpServletRequest request = new MockHttpServletRequest();
+		HandlerExecutionChain handlerExecutionChain = handlerMapping
+				.getHandlerExecutionChain(endpoint, request);
+		HandlerInterceptor[] interceptors = handlerExecutionChain.getInterceptors();
+		CloudFoundryEndpointHandlerMapping.CorsInterceptor corsInterceptor = (CloudFoundryEndpointHandlerMapping.CorsInterceptor) interceptors[0];
+		MockHttpServletResponse response = new MockHttpServletResponse();
+		corsInterceptor.preHandle(request, response, new Object());
+		Mockito.verify(corsProcessor).processRequest(corsConfiguration, request,
+				response);
+	}
+
 	@Test
 	public void getHandlerExecutionChainShouldHaveSecurityInterceptor() throws Exception {
 		CloudFoundrySecurityInterceptor securityInterceptor = Mockito
@@ -57,7 +79,7 @@ public class CloudFoundryEndpointHandlerMappingTests
 		HandlerExecutionChain handlerExecutionChain = handlerMapping
 				.getHandlerExecutionChain(endpoint, new MockHttpServletRequest());
 		HandlerInterceptor[] interceptors = handlerExecutionChain.getInterceptors();
-		assertThat(interceptors).contains(securityInterceptor);
+		assertThat(interceptors[1]).isEqualTo(securityInterceptor);
 	}
 
 	@Test