Fix the problem

Author: trask

instrumentation-api-incubator/src/main/java/io/opentelemetry/instrumentation/api/incubator/semconv/messaging/CapturedMessageHeadersUtil.java

@@ -5,31 +5,21 @@
 
 package io.opentelemetry.instrumentation.api.incubator.semconv.messaging;
 
-import static java.util.Collections.unmodifiableList;
-
 import io.opentelemetry.api.common.AttributeKey;
 import java.util.List;
-import java.util.Locale;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
-import java.util.stream.Collectors;
 
 final class CapturedMessageHeadersUtil {
 
  private static final ConcurrentMap<String, AttributeKey<List<String>>> attributeKeysCache =
  new ConcurrentHashMap<>();
 
- static List<String> lowercase(List<String> names) {
- return unmodifiableList(
- names.stream().map(s -> s.toLowerCase(Locale.ROOT)).collect(Collectors.toList()));
- }
-
  static AttributeKey<List<String>> attributeKey(String headerName) {
  return attributeKeysCache.computeIfAbsent(headerName, n -> createKey(n));
  }
 
  private static AttributeKey<List<String>> createKey(String headerName) {
- // headerName is always lowercase, see MessagingAttributesExtractor
  String key = "messaging.header." + headerName.replace('-', '_');
  return AttributeKey.stringArrayKey(key);
  }

instrumentation-api-incubator/src/main/java/io/opentelemetry/instrumentation/api/incubator/semconv/messaging/MessagingAttributesExtractor.java

@@ -13,6 +13,7 @@
 import io.opentelemetry.instrumentation.api.instrumenter.AttributesExtractor;
 import io.opentelemetry.instrumentation.api.internal.SpanKey;
 import io.opentelemetry.instrumentation.api.internal.SpanKeyProvider;
+import java.util.ArrayList;
 import java.util.List;
 import javax.annotation.Nullable;
 
@@ -85,7 +86,7 @@ public static <REQUEST, RESPONSE> MessagingAttributesExtractorBuilder<REQUEST, R
  List<String> capturedHeaders) {
  this.getter = getter;
  this.operation = operation;
- this.capturedHeaders = CapturedMessageHeadersUtil.lowercase(capturedHeaders);
+ this.capturedHeaders = new ArrayList<>(capturedHeaders);
  }
 
  @Override

instrumentation-api-incubator/src/main/java/io/opentelemetry/instrumentation/api/incubator/semconv/messaging/MessagingAttributesExtractorBuilder.java

@@ -30,8 +30,8 @@ public final class MessagingAttributesExtractorBuilder<REQUEST, RESPONSE> {
  * Configures the messaging headers that will be captured as span attributes.
  *
  * <p>The messaging header values will be captured under the {@code messaging.header.<name>}
- * attribute key. The {@code <name>} part in the attribute key is the normalized header name:
- * lowercase, with dashes replaced by underscores.
+ * attribute key. The {@code <name>} part in the attribute key is the header name with dashes
+ * replaced by underscores.
  *
  * @param capturedHeaders A list of messaging header names.
  */