add javadoc,unit test

Author: AlchemyDing

docs/apidiffs/current_vs_latest/opentelemetry-instrumentation-api.txt

@@ -1,2 +1,6 @@
 Comparing source compatibility of opentelemetry-instrumentation-api-2.11.0-SNAPSHOT.jar against opentelemetry-instrumentation-api-2.10.0.jar
-No changes.
++++  NEW CLASS: PUBLIC(+) FINAL(+) io.opentelemetry.instrumentation.api.semconv.util.SpanNames  (not serializable)
+	+++  CLASS FILE FORMAT VERSION: 52.0 <- n.a.
+	+++  NEW SUPERCLASS: java.lang.Object
+	+++  NEW METHOD: PUBLIC(+) STATIC(+) java.lang.String fromMethod(java.lang.reflect.Method)
+	+++  NEW METHOD: PUBLIC(+) STATIC(+) java.lang.String fromMethod(java.lang.Class<?>, java.lang.String)

instrumentation-api-incubator/src/main/java/io/opentelemetry/instrumentation/api/incubator/semconv/util/SpanNames.java

@@ -5,11 +5,7 @@
 
 package io.opentelemetry.instrumentation.api.incubator.semconv.util;
 
-import io.opentelemetry.instrumentation.api.internal.ClassNames;
-import io.opentelemetry.instrumentation.api.internal.cache.Cache;
 import java.lang.reflect.Method;
-import java.util.Map;
-import java.util.concurrent.ConcurrentHashMap;
 
 /**
  * This class has been stabilized and moved to {@link
@@ -18,33 +14,21 @@
 @Deprecated
 public final class SpanNames {
 
-  private static final Cache<Class<?>, Map<String, String>> spanNameCaches = Cache.weak();
-
   /**
    * This method is used to generate a span name based on a method. Anonymous classes are named
    * based on their parent.
    */
   public static String fromMethod(Method method) {
-    return fromMethod(method.getDeclaringClass(), method.getName());
+    return io.opentelemetry.instrumentation.api.semconv.util.SpanNames.fromMethod(method);
   }
 
   /**
    * This method is used to generate a span name based on a method. Anonymous classes are named
    * based on their parent.
    */
   public static String fromMethod(Class<?> clazz, String methodName) {
-    // the cache (ConcurrentHashMap) is naturally bounded by the number of methods in a class
-    Map<String, String> spanNameCache =
-        spanNameCaches.computeIfAbsent(clazz, c -> new ConcurrentHashMap<>());
-
-    // not using computeIfAbsent, because it would require a capturing (allocating) lambda
-    String spanName = spanNameCache.get(methodName);
-    if (spanName != null) {
-      return spanName;
-    }
-    spanName = ClassNames.simpleName(clazz) + "." + methodName;
-    spanNameCache.put(methodName, spanName);
-    return spanName;
+    return io.opentelemetry.instrumentation.api.semconv.util.SpanNames.fromMethod(
+        clazz, methodName);
   }
 
   private SpanNames() {}

instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/semconv/util/SpanNames.java

@@ -11,6 +11,7 @@
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 
+/** A utility class used to generate span names. */
 public final class SpanNames {
 
   private static final Cache<Class<?>, Map<String, String>> spanNameCaches = Cache.weak();

instrumentation-api/src/test/java/io/opentelemetry/instrumentation/api/semconv/util/SpanNamesTest.java

@@ -0,0 +1,25 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.instrumentation.api.semconv.util;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.lang.reflect.Method;
+import org.junit.jupiter.api.Test;
+
+class SpanNamesTest {
+  @Test
+  void testFromMethod() throws NoSuchMethodException {
+    Method method = TestClass.class.getMethod("test");
+    assertThat(SpanNames.fromMethod(method)).isEqualTo("TestClass.test");
+  }
+
+  static class TestClass {
+    private TestClass() {}
+
+    public void test() {}
+  }
+}