Rework Cloud Foundry actuator support behind a pluggable abstraction

Deprecate `EndpointExposure.CLOUD_FOUNDRY` and introduce an alternative
implementation based on a pluggable abstraction.

The new `EndpointExposureOutcomeContributor` interface may now be used
to influence `@OnAvailableEndpointCondition` exposure results. Several
infrastructure beans that previously used the condition have been
refactored to always be registered, but tolerate missing endpoints.

A new smoke test application has been added that demonstrates how the
abstraction can be used by a third-party.

Closes gh-41135

Co-authored-by: Phillip Webb <phil.webb@broadcom.com>

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-actuator-extension/build.gradle

@@ -0,0 +1,13 @@
+plugins {
+	id "java"
+	id "org.springframework.boot.conventions"
+}
+
+description = "Spring Boot Actuator Extension smoke test"
+
+dependencies {
+	implementation(project(":spring-boot-project:spring-boot-starters:spring-boot-starter-actuator"))
+	implementation(project(":spring-boot-project:spring-boot-starters:spring-boot-starter-web"))
+
+	testImplementation(project(":spring-boot-project:spring-boot-starters:spring-boot-starter-test"))
+}

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-actuator-extension/src/main/java/smoketest/actuator/extension/MyExtensionConfiguration.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2012-2024 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
+ *
+ *      https://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 smoketest.actuator.extension;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+
+import org.springframework.beans.factory.ObjectProvider;
+import org.springframework.boot.actuate.autoconfigure.endpoint.web.CorsEndpointProperties;
+import org.springframework.boot.actuate.autoconfigure.endpoint.web.WebEndpointProperties;
+import org.springframework.boot.actuate.endpoint.EndpointFilter;
+import org.springframework.boot.actuate.endpoint.invoke.OperationInvokerAdvisor;
+import org.springframework.boot.actuate.endpoint.invoke.ParameterValueMapper;
+import org.springframework.boot.actuate.endpoint.web.EndpointMediaTypes;
+import org.springframework.boot.actuate.endpoint.web.ExposableWebEndpoint;
+import org.springframework.boot.actuate.endpoint.web.WebEndpointsSupplier;
+import org.springframework.boot.actuate.endpoint.web.annotation.WebEndpointDiscoverer;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.env.Environment;
+import org.springframework.web.cors.CorsConfiguration;
+
+@Configuration(proxyBeanMethods = false)
+public class MyExtensionConfiguration {
+
+	@Bean
+	public MyExtensionWebMvcEndpointHandlerMapping myWebMvcEndpointHandlerMapping(
+			WebEndpointsSupplier webEndpointsSupplier, EndpointMediaTypes endpointMediaTypes,
+			ObjectProvider<CorsEndpointProperties> corsPropertiesProvider, WebEndpointProperties webEndpointProperties,
+			Environment environment, ApplicationContext applicationContext, ParameterValueMapper parameterMapper) {
+		CorsEndpointProperties corsProperties = corsPropertiesProvider.getIfAvailable();
+		CorsConfiguration corsConfiguration = (corsProperties != null) ? corsProperties.toCorsConfiguration() : null;
+		List<OperationInvokerAdvisor> invokerAdvisors = Collections.emptyList();
+		List<EndpointFilter<ExposableWebEndpoint>> filters = Collections
+			.singletonList(new MyExtensionEndpointFilter(environment));
+		WebEndpointDiscoverer discoverer = new WebEndpointDiscoverer(applicationContext, parameterMapper,
+				endpointMediaTypes, null, invokerAdvisors, filters);
+		Collection<ExposableWebEndpoint> endpoints = discoverer.getEndpoints();
+		return new MyExtensionWebMvcEndpointHandlerMapping(endpoints, endpointMediaTypes, corsConfiguration);
+	}
+
+}

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-actuator-extension/src/main/java/smoketest/actuator/extension/MyExtensionEndpointExposureOutcomeContributor.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2012-2024 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
+ *
+ *      https://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 smoketest.actuator.extension;
+
+import java.util.Set;
+
+import org.springframework.boot.actuate.autoconfigure.endpoint.condition.EndpointExposureOutcomeContributor;
+import org.springframework.boot.actuate.autoconfigure.endpoint.expose.EndpointExposure;
+import org.springframework.boot.actuate.endpoint.EndpointId;
+import org.springframework.boot.autoconfigure.condition.ConditionMessage.Builder;
+import org.springframework.boot.autoconfigure.condition.ConditionOutcome;
+import org.springframework.core.env.Environment;
+
+class MyExtensionEndpointExposureOutcomeContributor implements EndpointExposureOutcomeContributor {
+
+	private final MyExtensionEndpointFilter filter;
+
+	MyExtensionEndpointExposureOutcomeContributor(Environment environment) {
+		this.filter = new MyExtensionEndpointFilter(environment);
+	}
+
+	@Override
+	public ConditionOutcome getExposureOutcome(EndpointId endpointId, Set<EndpointExposure> exposures,
+			Builder message) {
+		if (exposures.contains(EndpointExposure.WEB) && this.filter.match(endpointId)) {
+			return ConditionOutcome.match(message.because("marked as exposed by a my extension '"
+					+ MyExtensionEndpointFilter.PROPERTY_PREFIX + "' property"));
+		}
+		return null;
+
+	}
+
+}

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-actuator-extension/src/main/java/smoketest/actuator/extension/MyExtensionEndpointFilter.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2012-2024 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
+ *
+ *      https://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 smoketest.actuator.extension;
+
+import org.springframework.boot.actuate.autoconfigure.endpoint.expose.IncludeExcludeEndpointFilter;
+import org.springframework.boot.actuate.endpoint.web.ExposableWebEndpoint;
+import org.springframework.core.env.Environment;
+
+class MyExtensionEndpointFilter extends IncludeExcludeEndpointFilter<ExposableWebEndpoint> {
+
+	static final String PROPERTY_PREFIX = "management.endpoints.myextension.exposure";
+
+	MyExtensionEndpointFilter(Environment environment) {
+		super(ExposableWebEndpoint.class, environment, PROPERTY_PREFIX, "*");
+	}
+
+}

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-actuator-extension/src/main/java/smoketest/actuator/extension/MyExtensionSecurityInterceptor.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2012-2024 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
+ *
+ *      https://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 smoketest.actuator.extension;
+
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.web.servlet.HandlerInterceptor;
+
+class MyExtensionSecurityInterceptor implements HandlerInterceptor {
+
+	@Override
+	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
+			throws Exception {
+		String auth = request.getHeader("Authorization");
+		if (!"Bearer secret".equals(auth)) {
+			response.sendError(HttpStatus.UNAUTHORIZED.value());
+			return false;
+		}
+		return true;
+	}
+
+}

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-actuator-extension/src/main/java/smoketest/actuator/extension/MyExtensionWebMvcEndpointHandlerMapping.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2012-2024 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
+ *
+ *      https://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 smoketest.actuator.extension;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+
+import org.springframework.boot.actuate.endpoint.web.EndpointLinksResolver;
+import org.springframework.boot.actuate.endpoint.web.EndpointMapping;
+import org.springframework.boot.actuate.endpoint.web.EndpointMediaTypes;
+import org.springframework.boot.actuate.endpoint.web.ExposableWebEndpoint;
+import org.springframework.boot.actuate.endpoint.web.Link;
+import org.springframework.boot.actuate.endpoint.web.servlet.AbstractWebMvcEndpointHandlerMapping;
+import org.springframework.web.bind.annotation.ResponseBody;
+import org.springframework.web.cors.CorsConfiguration;
+
+class MyExtensionWebMvcEndpointHandlerMapping extends AbstractWebMvcEndpointHandlerMapping {
+
+	private static final String PATH = "/myextension";
+
+	private final EndpointLinksResolver linksResolver;
+
+	MyExtensionWebMvcEndpointHandlerMapping(Collection<ExposableWebEndpoint> endpoints,
+			EndpointMediaTypes endpointMediaTypes, CorsConfiguration corsConfiguration) {
+		super(new EndpointMapping(PATH), endpoints, endpointMediaTypes, corsConfiguration, true);
+		this.linksResolver = new EndpointLinksResolver(endpoints, PATH);
+		setOrder(-100);
+	}
+
+	@Override
+	protected LinksHandler getLinksHandler() {
+		return new WebMvcLinksHandler();
+	}
+
+	@Override
+	protected void extendInterceptors(List<Object> interceptors) {
+		super.extendInterceptors(interceptors);
+		interceptors.add(0, new MyExtensionSecurityInterceptor());
+	}
+
+	class WebMvcLinksHandler implements LinksHandler {
+
+		@Override
+		@ResponseBody
+		public Map<String, Map<String, Link>> links(HttpServletRequest request, HttpServletResponse response) {
+			return Collections.singletonMap("_links", MyExtensionWebMvcEndpointHandlerMapping.this.linksResolver
+				.resolveLinks(request.getRequestURL().toString()));
+		}
+
+		@Override
+		public String toString() {
+			return "Actuator extension root web endpoint";
+		}
+
+	}
+
+}

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-actuator-extension/src/main/java/smoketest/actuator/extension/SampleActuatorExtensionApplication.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2012-2024 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
+ *
+ *      https://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 smoketest.actuator.extension;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication(proxyBeanMethods = false)
+public class SampleActuatorExtensionApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(SampleActuatorExtensionApplication.class, args);
+	}
+
+}

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-actuator-extension/src/main/resources/META-INF/spring.factories

@@ -0,0 +1,2 @@
+org.springframework.boot.actuate.autoconfigure.endpoint.condition.EndpointExposureOutcomeContributor=\
+smoketest.actuator.extension.MyExtensionEndpointExposureOutcomeContributor

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-actuator-extension/src/main/resources/application.properties

@@ -0,0 +1,4 @@
+spring.jmx.enabled=false
+management.endpoints.web.exposure.exclude=*
+management.endpoints.myextension.exposure.include=health,beans,configprops
+

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-actuator-extension/src/test/java/smoketest/actuator/extension/SampleActuatorExtensionApplicationTests.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2012-2024 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
+ *
+ *      https://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 smoketest.actuator.extension;
+
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.boot.test.web.client.LocalHostUriTemplateHandler;
+import org.springframework.boot.test.web.client.TestRestTemplate;
+import org.springframework.boot.web.client.RestTemplateBuilder;
+import org.springframework.core.env.Environment;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT, properties = { "server.error.include-message=always" })
+class SampleActuatorExtensionApplicationTests {
+
+	@Autowired
+	private Environment environment;
+
+	@Autowired
+	private TestRestTemplate restTemplate;
+
+	@Autowired
+	private RestTemplateBuilder restTemplateBuilder;
+
+	@Test
+	@SuppressWarnings("rawtypes")
+	void healthActuatorIsNotExposed() {
+		ResponseEntity<Map> entity = this.restTemplate.getForEntity("/actuator/health", Map.class);
+		assertThat(entity.getStatusCode()).isEqualTo(HttpStatus.NOT_FOUND);
+	}
+
+	@Test
+	@SuppressWarnings("rawtypes")
+	void healthExtensionWithAuthHeaderIsDenied() {
+		ResponseEntity<Map> entity = this.restTemplate.getForEntity("/myextension/health", Map.class);
+		assertThat(entity.getStatusCode()).isEqualTo(HttpStatus.UNAUTHORIZED);
+	}
+
+	@Test
+	@SuppressWarnings("rawtypes")
+	void healthExtensionWithAuthHeader() {
+		TestRestTemplate restTemplate = new TestRestTemplate(
+				this.restTemplateBuilder.defaultHeader("Authorization", "Bearer secret"));
+		restTemplate.setUriTemplateHandler(new LocalHostUriTemplateHandler(this.environment));
+		ResponseEntity<Map> entity = restTemplate.getForEntity("/myextension/health", Map.class);
+		assertThat(entity.getStatusCode()).isEqualTo(HttpStatus.OK);
+	}
+
+}