eugenp · jzheaux · Sep 5, 2025 · Aug 19, 2025 · Aug 19, 2025 · Aug 24, 2025
diff --git a/spring-boot-modules/spring-boot-3-observation/pom.xml b/spring-boot-modules/spring-boot-3-observation/pom.xml
@@ -103,12 +103,33 @@
                     </dependency>
                 </dependencies>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>21</source>
+                    <target>21</target>
+                </configuration>
+            </plugin>
         </plugins>
     </build>
 
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>io.micrometer</groupId>
+                <artifactId>micrometer-bom</artifactId>
+                <version>${micrometer.version}</version>
+                <type>pom</type>
+                <scope>import</scope>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
     <properties>
         <start-class>com.baeldung.samples.SimpleObservationApplication</start-class>
         <p6spy-spring-boot-starter.version>1.9.0</p6spy-spring-boot-starter.version>
+        <micrometer.version>1.15.3</micrometer.version>
     </properties>
 
 </project>
diff --git a/...les/spring-boot-3-observation/src/main/java/com/baeldung/micrometer/tags/Application.java b/...les/spring-boot-3-observation/src/main/java/com/baeldung/micrometer/tags/Application.java
@@ -0,0 +1,36 @@
+package com.baeldung.micrometer.tags;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.annotation.Bean;
+
+import io.micrometer.core.aop.CountedAspect;
+import io.micrometer.core.aop.CountedMeterTagAnnotationHandler;
+import io.micrometer.core.aop.MeterTagAnnotationHandler;
+import io.micrometer.core.aop.TimedAspect;
+
+@SpringBootApplication
+class Application {
+
+    public static void main(String[] args) {
+        SpringApplication.run(Application.class, args);
+    }
+
+    @Bean
+    public MeterTagAnnotationHandler meterTagAnnotationHandler() {
+        return new MeterTagAnnotationHandler(
+            aClass -> Object::toString,
+            aClass -> (exp, param) -> "");
+    }
+
+    @Bean
+    public CountedAspect countedAspect() {
+        CountedAspect aspect = new CountedAspect();
+        CountedMeterTagAnnotationHandler tagAnnotationHandler = new CountedMeterTagAnnotationHandler(
+            aClass -> Object::toString,
+            aClass -> (exp, param) -> "");
+        aspect.setMeterTagAnnotationHandler(tagAnnotationHandler);
+        return aspect;
+    }
+
+}
diff --git a/...ing-boot-3-observation/src/main/java/com/baeldung/micrometer/tags/dummy/DummyService.java b/...ing-boot-3-observation/src/main/java/com/baeldung/micrometer/tags/dummy/DummyService.java
@@ -0,0 +1,79 @@
+package com.baeldung.micrometer.tags.dummy;
+
+import java.util.concurrent.ThreadLocalRandom;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.stereotype.Service;
+
+import io.micrometer.core.annotation.Counted;
+import io.micrometer.core.annotation.Timed;
+import io.micrometer.core.aop.MeterTag;
+import io.micrometer.core.instrument.Counter;
+import io.micrometer.core.instrument.Meter;
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.Timer;
+
+@Service
+class DummyService {
+
+    private static final Logger log = LoggerFactory.getLogger(DummyService.class);
+
+    private final MeterRegistry meterRegistry;
+    private final Meter.MeterProvider<Counter> counterProvider;
+    private final Meter.MeterProvider<Timer> timerProvider;
+
+    public DummyService(MeterRegistry meterRegistry) {
+        this.meterRegistry = meterRegistry;
+
+        this.counterProvider = Counter.builder("bar.count")
+            .withRegistry(meterRegistry);
+        this.timerProvider = Timer.builder("bar.time")
+            .withRegistry(meterRegistry);
+    }
+
+    public String foo(String deviceType) {
+        log.info("foo({})", deviceType);
+
+        Counter.builder("foo.count")
+            .tag("device.type", deviceType)
+            .register(meterRegistry)
+            .increment();
+        String response = Timer.builder("foo.time")
+            .tag("device.type", deviceType)
+            .register(meterRegistry)
+            .record(this::invokeSomeLogic);
+
+        return response;
+    }
+
+    public String bar(String device) {
+        log.info("bar({})", device);
+
+        counterProvider.withTag("device.type", device)
+            .increment();
+        String response = timerProvider.withTag("device.type", device)
+            .record(this::invokeSomeLogic);
+
+        return response;
+    }
+
+    @Timed("buzz.time")
+    @Counted("buzz.count")
+    public String buzz(@MeterTag("device.type") String device) {
+        log.info("buzz({})", device);
+        return invokeSomeLogic();
+    }
+
+    private String invokeSomeLogic() {
+        long sleepMs = ThreadLocalRandom.current()
+            .nextInt(0, 100);
+        try {
+            Thread.sleep(sleepMs);
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+        return "dummy response";
+    }
+
+}
diff --git a/...-3-observation/src/main/java/com/baeldung/micrometer/tags/dummy/DummyStartupListener.java b/...-3-observation/src/main/java/com/baeldung/micrometer/tags/dummy/DummyStartupListener.java
@@ -0,0 +1,33 @@
+package com.baeldung.micrometer.tags.dummy;
+
+import java.util.List;
+import java.util.stream.IntStream;
+
+import org.springframework.boot.context.event.ApplicationReadyEvent;
+import org.springframework.context.event.EventListener;
+import org.springframework.stereotype.Component;
+
+@Component
+class DummyStartupListener {
+
+    private static final List<String> deviceTypes = List.of("desktop", "mobile", "tablet", "smart_tv", "wearable");
+
+    private final DummyService service;
+
+    @EventListener(ApplicationReadyEvent.class)
+    void sendRequests() {
+        IntStream.range(0, 100)
+            .map(it -> it % deviceTypes.size())
+            .mapToObj(deviceTypes::get)
+            .parallel()
+            .forEach(deviceType -> {
+                service.foo(deviceType);
+                service.bar(deviceType);
+                service.buzz(deviceType);
+            });
+    }
+
+    DummyStartupListener(DummyService service) {
+        this.service = service;
+    }
+}
diff --git a/spring-boot-modules/spring-boot-3-observation/src/main/resources/application.yml b/spring-boot-modules/spring-boot-3-observation/src/main/resources/application.yml
@@ -1,4 +1,7 @@
 management:
+  observations:
+    annotations:
+      enabled: true
   endpoints:
     web:
       exposure: