Reduce dependencies of spring-boot-actuator

spring-boot-project/spring-boot-tomcat/src/main/java/org/springframework/boot/tomcat/actuate/metrics/TomcatMetricsBinder.java

@@ -0,0 +1,96 @@
+/*
+ * Copyright 2012-2025 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.boot.tomcat.actuate.metrics;
+
+import java.util.Collections;
+
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.Tag;
+import io.micrometer.core.instrument.binder.tomcat.TomcatMetrics;
+import org.apache.catalina.Container;
+import org.apache.catalina.Context;
+import org.apache.catalina.Manager;
+
+import org.springframework.beans.factory.DisposableBean;
+import org.springframework.boot.context.event.ApplicationStartedEvent;
+import org.springframework.boot.tomcat.TomcatWebServer;
+import org.springframework.boot.web.server.WebServer;
+import org.springframework.boot.web.server.context.WebServerApplicationContext;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.ApplicationListener;
+
+/**
+ * Binds {@link TomcatMetrics} in response to the {@link ApplicationStartedEvent}.
+ *
+ * @author Andy Wilkinson
+ * @since 4.0.0
+ */
+public class TomcatMetricsBinder implements ApplicationListener<ApplicationStartedEvent>, DisposableBean {
+
+	private final MeterRegistry meterRegistry;
+
+	private final Iterable<Tag> tags;
+
+	private volatile TomcatMetrics tomcatMetrics;
+
+	public TomcatMetricsBinder(MeterRegistry meterRegistry) {
+		this(meterRegistry, Collections.emptyList());
+	}
+
+	public TomcatMetricsBinder(MeterRegistry meterRegistry, Iterable<Tag> tags) {
+		this.meterRegistry = meterRegistry;
+		this.tags = tags;
+	}
+
+	@Override
+	public void onApplicationEvent(ApplicationStartedEvent event) {
+		ApplicationContext applicationContext = event.getApplicationContext();
+		Manager manager = findManager(applicationContext);
+		this.tomcatMetrics = new TomcatMetrics(manager, this.tags);
+		this.tomcatMetrics.bindTo(this.meterRegistry);
+	}
+
+	private Manager findManager(ApplicationContext applicationContext) {
+		if (applicationContext instanceof WebServerApplicationContext webServerApplicationContext) {
+			WebServer webServer = webServerApplicationContext.getWebServer();
+			if (webServer instanceof TomcatWebServer tomcatWebServer) {
+				Context context = findContext(tomcatWebServer);
+				if (context != null) {
+					return context.getManager();
+				}
+			}
+		}
+		return null;
+	}
+
+	private Context findContext(TomcatWebServer tomcatWebServer) {
+		for (Container container : tomcatWebServer.getTomcat().getHost().findChildren()) {
+			if (container instanceof Context context) {
+				return context;
+			}
+		}
+		return null;
+	}
+
+	@Override
+	public void destroy() {
+		if (this.tomcatMetrics != null) {
+			this.tomcatMetrics.close();
+		}
+	}
+
+}

spring-boot-project/spring-boot-tomcat/src/main/java/org/springframework/boot/tomcat/actuate/metrics/package-info.java

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2012-2019 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.
+ */
+
+/**
+ * Tomcat metrics.
+ */
+package org.springframework.boot.tomcat.actuate.metrics;

spring-boot-project/spring-boot-tomcat/src/test/java/org/springframework/boot/actuate/metrics/web/tomcat/TomcatMetricsBinderTests.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2012-2020 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.boot.actuate.metrics.web.tomcat;
+
+import io.micrometer.core.instrument.MeterRegistry;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.tomcat.actuate.metrics.TomcatMetricsBinder;
+
+import static org.mockito.Mockito.mock;
+
+/**
+ * Tests for {@link TomcatMetricsBinder}.
+ *
+ * @author Andy Wilkinson
+ */
+class TomcatMetricsBinderTests {
+
+	private final MeterRegistry meterRegistry = mock(MeterRegistry.class);
+
+	@Test
+	void destroySucceedsWhenCalledBeforeApplicationHasStarted() {
+		new TomcatMetricsBinder(this.meterRegistry).destroy();
+	}
+
+}