stabilise spanNames

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

@@ -0,0 +1,48 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+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;
+
+@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());
+  }
+
+  /**
+   * 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;
+  }
+
+  private SpanNames() {}
+}