GH-87 - Expose module structure as actuator endpoint.

Introduce Spring Modulith Actuator module to expose the application module structure as Spring Boot actuator. This required a Spring Modulith Runtime module to be extracted from the Spring Modulith Observability one. The former now contains the auto-configured ApplicationRuntime and ApplicationModulesRuntime bean instances to be able to bootstrap a ApplicationModules asynchronously on application startup. The actuator module then contains a Spring Boot @Endpoint implementation consuming the ApplicationModules to render JSON describing the application module structure.

spring-modulith-runtime/src/main/java/org/springframework/modulith/runtime/ApplicationModulesRuntime.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2022 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 org.springframework.modulith.runtime;
+
+import lombok.NonNull;
+import lombok.RequiredArgsConstructor;
+
+import java.util.function.Supplier;
+
+import org.springframework.modulith.model.ApplicationModules;
+
+/**
+ * Bootstrap type to make sure we only bootstrap the initialization of a {@link ApplicationModules} instance once per
+ * application class.
+ *
+ * @author Oliver Drotbohm
+ */
+@RequiredArgsConstructor
+public class ApplicationModulesRuntime implements Supplier<ApplicationModules> {
+
+	private final @NonNull Supplier<ApplicationModules> modules;
+	private final @NonNull ApplicationRuntime runtime;
+
+	/*
+	 * (non-Javadoc)
+	 * @see java.util.function.Supplier#get()
+	 */
+	@Override
+	public ApplicationModules get() {
+		return modules.get();
+	}
+
+	/**
+	 * Returns whether a given {@link Class} is considered an application one (versus Framework ones).
+	 *
+	 * @param type
+	 * @return
+	 */
+	public boolean isApplicationClass(Class<?> type) {
+		return runtime.isApplicationClass(type);
+	}
+
+	/**
+	 * Returns the actual user class for a given bean and bean name.
+	 *
+	 * @param bean must not be {@literal null}.
+	 * @param beanName must not be {@literal null} or empty.
+	 * @return will never be {@literal null}.
+	 */
+	public Class<?> getUserClass(Object bean, String beanName) {
+		return runtime.getUserClass(bean, beanName);
+	}
+}

spring-modulith-runtime/src/main/java/org/springframework/modulith/runtime/ApplicationRuntime.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2022 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 org.springframework.modulith.runtime;
+
+/**
+ * Abstraction of the application runtime environment. Primarily to keep references to Spring Boot out of the core
+ * observability implementation.
+ *
+ * @author Oliver Drotbohm
+ */
+public interface ApplicationRuntime {
+
+	/**
+	 * Returns the identifier of the application.
+	 *
+	 * @return will never be {@literal null}.
+	 */
+	String getId();
+
+	/**
+	 * Returns the primary application class.
+	 *
+	 * @return will never be {@literal null}.
+	 */
+	Class<?> getMainApplicationClass();
+
+	/**
+	 * Obtain the end user class for the given bean and bean name. Necessary to reveal the actual user type from
+	 * potentially proxied instances.
+	 *
+	 * @param bean must not be {@literal null}.
+	 * @param beanName must not be {@literal null} or empty.
+	 * @return will never be {@literal null}.
+	 */
+	Class<?> getUserClass(Object bean, String beanName);
+
+	/**
+	 * Returns whether the given type is an application class, i.e. user code in one of the application packages.
+	 *
+	 * @param type must not be {@literal null}.
+	 * @return whether the given type is an application class, i.e. user code in one of the application packages.
+	 */
+	boolean isApplicationClass(Class<?> type);
+}

spring-modulith-runtime/src/main/java/org/springframework/modulith/runtime/autoconfigure/SpringBootApplicationRuntime.java

@@ -0,0 +1,92 @@
+/*
+ * Copyright 2022 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 org.springframework.modulith.runtime.autoconfigure;
+
+import lombok.RequiredArgsConstructor;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+import org.springframework.boot.autoconfigure.AutoConfigurationPackages;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.ApplicationContext;
+import org.springframework.modulith.runtime.ApplicationRuntime;
+import org.springframework.util.ClassUtils;
+
+/**
+ * @author Oliver Drotbohm
+ */
+@RequiredArgsConstructor
+class SpringBootApplicationRuntime implements ApplicationRuntime {
+
+	private static final Map<String, Boolean> APPLICATION_CLASSES = new ConcurrentHashMap<>();
+
+	private final ApplicationContext context;
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.modulith.observability.ApplicationRuntime#getId()
+	 */
+	@Override
+	public String getId() {
+		return context.getId();
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.modulith.observability.ApplicationRuntime#getApplicationClass()
+	 */
+	@Override
+	public Class<?> getMainApplicationClass() {
+
+		var mainBeanNames = context.getBeanNamesForAnnotation(SpringBootApplication.class);
+
+		return context.getType(mainBeanNames[0]);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.modulith.observability.ApplicationRuntime#getBeanUserClass(java.lang.Object, java.lang.String)
+	 */
+	@Override
+	public Class<?> getUserClass(Object bean, String beanName) {
+
+		var beanType = context.containsBean(beanName)
+				? context.getType(beanName)
+				: bean.getClass();
+
+		return ClassUtils.getUserClass(beanType);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.modulith.observability.ApplicationRuntime#isApplicationClass(java.lang.Class)
+	 */
+	@Override
+	public boolean isApplicationClass(Class<?> type) {
+
+		return APPLICATION_CLASSES.computeIfAbsent(type.getName(),
+				it -> {
+
+					if (it.startsWith("org.springframework")) {
+						return false;
+					}
+
+					return it.startsWith(getMainApplicationClass().getPackage().getName())
+							|| AutoConfigurationPackages.get(context).stream().anyMatch(pkg -> it.startsWith(pkg));
+				});
+	}
+}

spring-modulith-runtime/src/main/java/org/springframework/modulith/runtime/autoconfigure/SpringModulithRuntimeAutoConfiguration.java

@@ -0,0 +1,92 @@
+/*
+ * Copyright 2022 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 org.springframework.modulith.runtime.autoconfigure;
+
+import lombok.extern.slf4j.Slf4j;
+
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.function.Supplier;
+
+import org.springframework.boot.autoconfigure.AutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.modulith.model.ApplicationModule;
+import org.springframework.modulith.model.ApplicationModules;
+import org.springframework.modulith.runtime.ApplicationModulesRuntime;
+import org.springframework.modulith.runtime.ApplicationRuntime;
+
+/**
+ * Auto-configuration to register a {@link SpringBootApplicationRuntime} and {@link ApplicationModulesRuntime} as Spring
+ * Bean.
+ *
+ * @author Oliver Drotbohm
+ */
+@Slf4j
+@AutoConfiguration
+class SpringModulithRuntimeAutoConfiguration {
+
+	@Bean
+	@ConditionalOnMissingBean(ApplicationRuntime.class)
+	SpringBootApplicationRuntime modulithsApplicationRuntime(ApplicationContext context) {
+		return new SpringBootApplicationRuntime(context);
+	}
+
+	@Bean
+	@ConditionalOnMissingBean
+	ApplicationModulesRuntime modulesRuntime(ApplicationRuntime runtime) {
+
+		var mainClass = runtime.getMainApplicationClass();
+		var modules = Executors.newFixedThreadPool(1)
+				.submit(() -> SpringModulithRuntimeAutoConfiguration.initializeApplicationModules(mainClass));
+
+		return new ApplicationModulesRuntime(toSupplier(modules), runtime);
+	}
+
+	private static ApplicationModules initializeApplicationModules(Class<?> applicationMainClass) {
+
+		LOG.debug("Obtaining Spring Modulith application modules…");
+
+		var result = ApplicationModules.of(applicationMainClass);
+		var numberOfModules = result.stream().count();
+
+		if (numberOfModules == 0) {
+
+			LOG.warn("No application modules detected!");
+
+		} else {
+
+			LOG.debug("Detected {} application modules: {}", //
+					result.stream().count(), //
+					result.stream().map(ApplicationModule::getName).toList());
+		}
+
+		return result;
+	}
+
+	private static Supplier<ApplicationModules> toSupplier(Future<ApplicationModules> modules) {
+
+		return () -> {
+			try {
+				return modules.get();
+			} catch (Exception o_O) {
+				throw new RuntimeException(o_O);
+				// TODO: handle exception
+			}
+		};
+	}
+}

spring-modulith-runtime/src/main/resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports

@@ -0,0 +1 @@
+org.springframework.modulith.runtime.autoconfigure.SpringModulithRuntimeAutoConfiguration

spring-modulith-runtime/src/test/java/org/springframework/modulith/runtime/autoconfigure/SpringBootApplicationRuntimeUnitTests.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2022 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 org.springframework.modulith.runtime.autoconfigure;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.aop.framework.ProxyFactory;
+import org.springframework.context.ApplicationContext;
+import org.springframework.modulith.runtime.ApplicationRuntime;
+
+/**
+ * Unit tests for {@link SpringBootApplicationRuntime}.
+ *
+ * @author Oliver Drotbohm
+ */
+@ExtendWith(MockitoExtension.class)
+class SpringBootApplicationRuntimeUnitTests {
+
+	@Mock ApplicationContext context;
+
+	@Test // GH-87
+	void extractsUserTypeFromClassBasedProxy() {
+
+		Object proxy = new ProxyFactory(new Sample()).getProxy();
+		ApplicationRuntime runtime = new SpringBootApplicationRuntime(context);
+
+		assertThat(proxy.getClass()).isNotEqualTo(Sample.class);
+		assertThat(runtime.getUserClass(proxy, "sample")).isEqualTo(Sample.class);
+	}
+
+	static class Sample {}
+}

spring-modulith-runtime/src/test/java/org/springframework/modulith/runtime/autoconfigure/SpringModulithRuntimeAutoConfigurationIntegrationTests.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2022 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 org.springframework.modulith.runtime.autoconfigure;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.ApplicationContext;
+import org.springframework.modulith.runtime.ApplicationModulesRuntime;
+import org.springframework.modulith.runtime.ApplicationRuntime;
+
+/**
+ * Integration thest for {@link SpringModulithRuntimeAutoConfiguration}.
+ *
+ * @author Oliver Drotbohm
+ */
+@SpringBootTest
+class SpringModulithRuntimeAutoConfigurationIntegrationTests {
+
+	@SpringBootApplication
+	static class SampleApp {}
+
+	@Autowired ApplicationContext context;
+
+	@Test // GH-87
+	void bootstrapRegistersRuntimeInstances() {
+
+		assertThat(context.getBean(ApplicationRuntime.class)).isNotNull();
+		assertThat(context.getBean(ApplicationModulesRuntime.class)).isNotNull();
+	}
+}