Lazily allocate HashMap in PathMatchingHttpServletRequestWrapper

The wrapper is created on every request to isolate attribute side effects
during handler mapping lookups. Previously, a HashMap was eagerly allocated
even when no handler mapping matched (and thus no attributes were set).
This defers the HashMap allocation to the first setAttribute call, avoiding
the cost of a HashMap with its 16-entry Node array on requests that don't
match any handler mapping.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: dougqh

dd-java-agent/instrumentation/spring/spring-webmvc/spring-webmvc-3.1/src/main/java/datadog/trace/instrumentation/springweb/PathMatchingHttpServletRequestWrapper.java

@@ -6,28 +6,35 @@
 import javax.servlet.http.HttpServletRequestWrapper;
 
 class PathMatchingHttpServletRequestWrapper extends HttpServletRequestWrapper {
-  private final Map<String, Object> localAttributes = new HashMap<>();
+  private Map<String, Object> localAttributes;
 
   public PathMatchingHttpServletRequestWrapper(HttpServletRequest request) {
     super(request);
   }
 
   @Override
   public Object getAttribute(String name) {
-    final Object ret = localAttributes.get(name);
-    if (ret == null) {
-      return super.getAttribute(name);
+    if (localAttributes != null) {
+      final Object ret = localAttributes.get(name);
+      if (ret != null) {
+        return ret;
+      }
     }
-    return ret;
+    return super.getAttribute(name);
   }
 
   @Override
   public void setAttribute(String name, Object o) {
+    if (localAttributes == null) {
+      localAttributes = new HashMap<>();
+    }
     localAttributes.put(name, o);
   }
 
   @Override
   public void removeAttribute(String name) {
-    localAttributes.remove(name);
+    if (localAttributes != null) {
+      localAttributes.remove(name);
+    }
   }
 }

dd-java-agent/instrumentation/spring/spring-webmvc/spring-webmvc-6.0/src/main/java17/datadog/trace/instrumentation/springweb6/PathMatchingHttpServletRequestWrapper.java

@@ -6,28 +6,35 @@
 import java.util.Map;
 
 class PathMatchingHttpServletRequestWrapper extends HttpServletRequestWrapper {
-  private final Map<String, Object> localAttributes = new HashMap<>();
+  private Map<String, Object> localAttributes;
 
   public PathMatchingHttpServletRequestWrapper(HttpServletRequest request) {
     super(request);
   }
 
   @Override
   public Object getAttribute(String name) {
-    final Object ret = localAttributes.get(name);
-    if (ret == null) {
-      return super.getAttribute(name);
+    if (localAttributes != null) {
+      final Object ret = localAttributes.get(name);
+      if (ret != null) {
+        return ret;
+      }
     }
-    return ret;
+    return super.getAttribute(name);
   }
 
   @Override
   public void setAttribute(String name, Object o) {
+    if (localAttributes == null) {
+      localAttributes = new HashMap<>();
+    }
     localAttributes.put(name, o);
   }
 
   @Override
   public void removeAttribute(String name) {
-    localAttributes.remove(name);
+    if (localAttributes != null) {
+      localAttributes.remove(name);
+    }
   }
 }