MeterTags wrapper to support multiple MeterTag-s on a single method p…

…arameter (#5055)

Resolves gh-4081

---------

Co-authored-by: Maksym Symonov <maksym.symonov@nordstrom.com>

micrometer-commons/src/main/java/io/micrometer/common/annotation/AnnotationUtils.java

@@ -17,7 +17,9 @@
 
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Method;
-import java.util.ArrayList;
+import java.lang.reflect.Parameter;
+import java.util.Arrays;
+import java.util.LinkedList;
 import java.util.List;
 
 /**
@@ -36,16 +38,15 @@ private AnnotationUtils() {
 
     static List<AnnotatedParameter> findAnnotatedParameters(Class<? extends Annotation> annotationClazz, Method method,
             Object[] args) {
-        Annotation[][] parameters = method.getParameterAnnotations();
-        List<AnnotatedParameter> result = new ArrayList<>();
-        int i = 0;
-        for (Annotation[] parameter : parameters) {
-            for (Annotation parameter2 : parameter) {
-                if (annotationClazz.isAssignableFrom(parameter2.annotationType())) {
-                    result.add(new AnnotatedParameter(i, parameter2, args[i]));
-                }
-            }
-            i++;
+        Parameter[] parameters = method.getParameters();
+        List<AnnotatedParameter> result = new LinkedList<>();
+        for (int i = 0; i < parameters.length; i++) {
+            Parameter parameter = parameters[i];
+            Annotation[] annotations = parameter.getAnnotationsByType(annotationClazz);
+            final int parameterIndex = i;
+            Arrays.stream(annotations)
+                .map(annotation -> new AnnotatedParameter(parameterIndex, annotation, args[parameterIndex]))
+                .forEach(result::add);
         }
         return result;
     }

micrometer-core/src/main/java/io/micrometer/core/aop/MeterTag.java

@@ -38,6 +38,7 @@
 @Retention(RetentionPolicy.RUNTIME)
 @Inherited
 @Target(ElementType.PARAMETER)
+@Repeatable(MeterTags.class)
 public @interface MeterTag {
 
     /**

micrometer-core/src/main/java/io/micrometer/core/aop/MeterTags.java

@@ -0,0 +1,46 @@
+/**
+ * Copyright 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 io.micrometer.core.aop;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Inherited;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Container annotation that aggregates several {@link MeterTag} annotations.
+ *
+ * Can be used natively, declaring several nested {@link MeterTag} annotations. Can also
+ * be used in conjunction with Java 8's support for repeatable annotations, where
+ * {@link MeterTag} can simply be declared several times on the same parameter, implicitly
+ * generating this container annotation.
+ *
+ * @author Maksym Symonov
+ * @author Marcin Grzejszczak
+ * @since 1.14.0
+ * @see MeterTag
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Inherited
+@Target(ElementType.PARAMETER)
+@Documented
+public @interface MeterTags {
+
+    MeterTag[] value();
+
+}

micrometer-core/src/test/java/io/micrometer/core/aop/TimedAspectTest.java

@@ -457,6 +457,49 @@ void meterTagsWithExpression(AnnotatedTestClass annotatedClass) {
             assertThat(registry.get("method.timed").tag("test", "hello characters").timer().count()).isEqualTo(1);
         }
 
+        @ParameterizedTest
+        @EnumSource(AnnotatedTestClass.class)
+        void multipleMeterTagsWithExpression(AnnotatedTestClass annotatedClass) {
+            MeterRegistry registry = new SimpleMeterRegistry();
+            TimedAspect timedAspect = new TimedAspect(registry);
+            timedAspect.setMeterTagAnnotationHandler(meterTagAnnotationHandler);
+
+            AspectJProxyFactory pf = new AspectJProxyFactory(annotatedClass.newInstance());
+            pf.addAspect(timedAspect);
+
+            MeterTagClassInterface service = pf.getProxy();
+
+            service.getMultipleAnnotationsForTagValueExpression(new DataHolder("zxe", "qwe"));
+
+            assertThat(registry.get("method.timed")
+                .tag("value1", "value1: zxe")
+                .tag("value2", "value2: qwe")
+                .timer()
+                .count()).isEqualTo(1);
+        }
+
+        @ParameterizedTest
+        @EnumSource(AnnotatedTestClass.class)
+        void multipleMeterTagsWithinContainerWithExpression(AnnotatedTestClass annotatedClass) {
+            MeterRegistry registry = new SimpleMeterRegistry();
+            TimedAspect timedAspect = new TimedAspect(registry);
+            timedAspect.setMeterTagAnnotationHandler(meterTagAnnotationHandler);
+
+            AspectJProxyFactory pf = new AspectJProxyFactory(annotatedClass.newInstance());
+            pf.addAspect(timedAspect);
+
+            MeterTagClassInterface service = pf.getProxy();
+
+            service.getMultipleAnnotationsWithContainerForTagValueExpression(new DataHolder("zxe", "qwe"));
+
+            assertThat(registry.get("method.timed")
+                .tag("value1", "value1: zxe")
+                .tag("value2", "value2: qwe")
+                .tag("value3", "value3: ZXEQWE")
+                .timer()
+                .count()).isEqualTo(1);
+        }
+
         @Test
         void meterTagOnPackagePrivateMethod() {
             MeterRegistry registry = new SimpleMeterRegistry();
@@ -525,6 +568,17 @@ void getAnnotationForTagValueExpression(
             @Timed
             void getAnnotationForArgumentToString(@MeterTag("test") Long param);
 
+            @Timed
+            void getMultipleAnnotationsForTagValueExpression(
+                    @MeterTag(key = "value1", expression = "'value1: ' + value1") @MeterTag(key = "value2",
+                            expression = "'value2: ' + value2") DataHolder param);
+
+            @Timed
+            void getMultipleAnnotationsWithContainerForTagValueExpression(@MeterTags({
+                    @MeterTag(key = "value1", expression = "'value1: ' + value1"),
+                    @MeterTag(key = "value2", expression = "'value2: ' + value2"), @MeterTag(key = "value3",
+                            expression = "'value3: ' + value1.toUpperCase + value2.toUpperCase") }) DataHolder param);
+
         }
 
         static class MeterTagClass implements MeterTagClassInterface {
@@ -550,6 +604,22 @@ public void getAnnotationForArgumentToString(@MeterTag("test") Long param) {
             void getAnnotationForPackagePrivateMethod(@MeterTag("foo") String foo) {
             }
 
+            @Timed
+            @Override
+            public void getMultipleAnnotationsForTagValueExpression(
+                    @MeterTag(key = "value1", expression = "'value1: ' + value1") @MeterTag(key = "value2",
+                            expression = "'value2: ' + value2") DataHolder param) {
+
+            }
+
+            @Timed
+            @Override
+            public void getMultipleAnnotationsWithContainerForTagValueExpression(@MeterTags({
+                    @MeterTag(key = "value1", expression = "'value1: ' + value1"),
+                    @MeterTag(key = "value2", expression = "'value2: ' + value2"), @MeterTag(key = "value3",
+                            expression = "'value3: ' + value1.toUpperCase + value2.toUpperCase") }) DataHolder param) {
+            }
+
         }
 
         static class MeterTagClassChild implements MeterTagClassInterface {
@@ -569,6 +639,18 @@ public void getAnnotationForTagValueExpression(String test) {
             public void getAnnotationForArgumentToString(Long param) {
             }
 
+            @Timed
+            @Override
+            public void getMultipleAnnotationsForTagValueExpression(DataHolder param) {
+
+            }
+
+            @Timed
+            @Override
+            public void getMultipleAnnotationsWithContainerForTagValueExpression(DataHolder param) {
+
+            }
+
         }
 
         static class MeterTagSuper {
@@ -699,4 +781,25 @@ public void call() {
 
     }
 
+    public static final class DataHolder {
+
+        private final String value1;
+
+        private final String value2;
+
+        private DataHolder(String value1, String value2) {
+            this.value1 = value1;
+            this.value2 = value2;
+        }
+
+        public String getValue1() {
+            return value1;
+        }
+
+        public String getValue2() {
+            return value2;
+        }
+
+    }
+
 }