Fix #12296 by partial revert of "Fixes #12289 - Improve ConcurrentPoo…

…l concurrency. (#12290)"

This reverts/modified parts of commit 115ee1c.

jetty-core/jetty-server/src/main/java/org/eclipse/jetty/server/handler/ContextHandler.java

@@ -653,11 +653,11 @@ protected void exitScope(Request request, Context lastContext, ClassLoader lastL
  */
  protected void notifyExitScope(Request request)
  {
- for (ContextScopeListener listener : TypeUtil.reverse(_contextListeners))
+ for (ListIterator<ContextScopeListener> i = TypeUtil.listIteratorAtEnd(_contextListeners); i.hasPrevious();)
  {
  try
  {
- listener.exitScope(_context, request);
+ i.previous().exitScope(_context, request);
  }
  catch (Throwable e)
  {

jetty-core/jetty-util/src/main/java/org/eclipse/jetty/util/TypeUtil.java

@@ -34,6 +34,7 @@
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
+import java.util.ListIterator;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.ServiceConfigurationError;
@@ -64,6 +65,7 @@ public class TypeUtil
  public static final int CR = '\r';
  public static final int LF = '\n';
  private static final Pattern TRAILING_DIGITS = Pattern.compile("^\\D*(\\d+)$");
+ private static final ListIterator<?> EMPTY_LIST_ITERATOR = Collections.EMPTY_LIST.listIterator();
 
  private static final HashMap<String, Class<?>> name2Class = new HashMap<>();
 
@@ -174,18 +176,35 @@ public static <T> List<T> asList(T[] a)
  }
 
  /**
- * <p>Returns a new list with the elements of the specified list in reverse order.</p>
- * <p>The specified list is not modified, differently from {@link Collections#reverse(List)}.</p>
- *
- * @param list the list whose elements are to be reversed
- * @return a new list with the elements in reverse order
+ * <p>Returns a {@link ListIterator} positioned at the last item in a list</p>
+ * <p>The method is safe for concurrent modifications iff the list iterator itself is safe.</p>
+ * @param list the list
  * @param <T> the element type
+ * @return A {@link ListIterator} with {@link ListIterator#hasNext()} that would have return {@code false}
+ * at the snapshot of the list represented by this call.
  */
- public static <T> List<T> reverse(List<T> list)
+ public static <T> ListIterator<T> listIteratorAtEnd(List<T> list)
  {
- List<T> result = new ArrayList<>(list);
- Collections.reverse(result);
- return result;
+ try
+ {
+ int size = list.size();
+ if (size == 0)
+ {
+ @SuppressWarnings("unchecked")
+ ListIterator<T> emptyListIterator = (ListIterator<T>)EMPTY_LIST_ITERATOR;
+ return emptyListIterator;
+ }
+ return list.listIterator(size);
+ }
+ catch (IndexOutOfBoundsException e)
+ {
+ // list was concurrently modified, so do this the hard way
+ ListIterator<T> i = list.listIterator();
+ while (i.hasNext())
+ i.next();
+
+ return i;
+ }
  }
 
  /**

jetty-ee10/jetty-ee10-servlet/src/main/java/org/eclipse/jetty/ee10/servlet/ServletContextHandler.java

@@ -31,6 +31,7 @@
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
+import java.util.ListIterator;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
@@ -519,11 +520,11 @@ public void contextDestroyed() throws Exception
  //Call context listeners
  Throwable multiException = null;
  ServletContextEvent event = new ServletContextEvent(getServletContext());
- for (ServletContextListener listener : TypeUtil.reverse(_destroyServletContextListeners))
+ for (ListIterator<ServletContextListener> i = TypeUtil.listIteratorAtEnd(_destroyServletContextListeners); i.hasPrevious();)
  {
  try
  {
- callContextDestroyed(listener, event);
+ callContextDestroyed(i.previous(), event);
  }
  catch (Exception x)
  {
@@ -574,17 +575,17 @@ protected void requestDestroyed(Request baseRequest, HttpServletRequest request)
  if (!_servletRequestListeners.isEmpty())
  {
  final ServletRequestEvent sre = new ServletRequestEvent(getServletContext(), request);
- for (ServletRequestListener listener : TypeUtil.reverse(_servletRequestListeners))
+ for (ListIterator<ServletRequestListener> i = TypeUtil.listIteratorAtEnd(_servletRequestListeners); i.hasPrevious();)
  {
- listener.requestDestroyed(sre);
+ i.previous().requestDestroyed(sre);
  }
  }
 
  if (!_servletRequestAttributeListeners.isEmpty())
  {
- for (ServletRequestAttributeListener listener : TypeUtil.reverse(_servletRequestAttributeListeners))
+ for (ListIterator<ServletRequestAttributeListener> i = TypeUtil.listIteratorAtEnd(_servletRequestAttributeListeners); i.hasPrevious();)
  {
- scopedRequest.removeEventListener(listener);
+ scopedRequest.removeEventListener(i.previous());
  }
  }
  }
@@ -1223,11 +1224,11 @@ protected void notifyExitScope(Request request)
  ServletContextRequest scopedRequest = Request.as(request, ServletContextRequest.class);
  if (!_contextListeners.isEmpty())
  {
- for (ServletContextScopeListener listener : TypeUtil.reverse(_contextListeners))
+ for (ListIterator<ServletContextScopeListener> i = TypeUtil.listIteratorAtEnd(_contextListeners); i.hasPrevious(); )
  {
  try
  {
- listener.exitScope(getContext(), scopedRequest);
+ i.previous().exitScope(getContext(), scopedRequest);
  }
  catch (Throwable e)
  {

jetty-ee10/jetty-ee10-servlet/src/main/java/org/eclipse/jetty/ee10/servlet/SessionHandler.java

@@ -19,6 +19,7 @@
 import java.util.EventListener;
 import java.util.Iterator;
 import java.util.List;
+import java.util.ListIterator;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
@@ -570,9 +571,9 @@ public void onSessionDestroyed(Session session)
  getSessionContext().run(() ->
  {
  HttpSessionEvent event = new HttpSessionEvent(session.getApi());
- for (HttpSessionListener listener : TypeUtil.reverse(_sessionListeners))
+ for (ListIterator<HttpSessionListener> i = TypeUtil.listIteratorAtEnd(_sessionListeners); i.hasPrevious();)
  {
- listener.sessionDestroyed(event);
+ i.previous().sessionDestroyed(event);
  }
  });
  }

jetty-ee9/jetty-ee9-nested/src/main/java/org/eclipse/jetty/ee9/nested/ContextHandler.java

@@ -29,6 +29,7 @@
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
+import java.util.ListIterator;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
@@ -1000,17 +1001,17 @@ protected void requestDestroyed(Request baseRequest, HttpServletRequest request)
  if (!_servletRequestListeners.isEmpty())
  {
  final ServletRequestEvent sre = new ServletRequestEvent(_apiContext, request);
- for (ServletRequestListener listener : TypeUtil.reverse(_servletRequestListeners))
+ for (ListIterator<ServletRequestListener> i = TypeUtil.listIteratorAtEnd(_servletRequestListeners); i.hasPrevious();)
  {
- listener.requestDestroyed(sre);
+ i.previous().requestDestroyed(sre);
  }
  }
 
  if (!_servletRequestAttributeListeners.isEmpty())
  {
- for (ServletRequestAttributeListener listener : TypeUtil.reverse(_servletRequestAttributeListeners))
+ for (ListIterator<ServletRequestAttributeListener> i = TypeUtil.listIteratorAtEnd(_servletRequestAttributeListeners); i.hasPrevious();)
  {
- baseRequest.removeEventListener(listener);
+ baseRequest.removeEventListener(i.previous());
  }
  }
  }
@@ -1070,11 +1071,11 @@ protected void exitScope(Request request)
  {
  if (!_contextListeners.isEmpty())
  {
- for (ContextScopeListener listener : TypeUtil.reverse(_contextListeners))
+ for (ListIterator<ContextScopeListener> i = TypeUtil.listIteratorAtEnd(_contextListeners); i.hasPrevious();)
  {
  try
  {
- listener.exitScope(_apiContext, request);
+ i.previous().exitScope(_apiContext, request);
  }
  catch (Throwable e)
  {

jetty-ee9/jetty-ee9-nested/src/main/java/org/eclipse/jetty/ee9/nested/SessionHandler.java

@@ -20,6 +20,7 @@
 import java.util.Enumeration;
 import java.util.EventListener;
 import java.util.List;
+import java.util.ListIterator;
 import java.util.Set;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.function.Function;
@@ -835,9 +836,9 @@ public void onSessionDestroyed(Session session)
  Runnable r = () ->
  {
  HttpSessionEvent event = new HttpSessionEvent(session.getApi());
- for (HttpSessionListener listener : TypeUtil.reverse(_sessionListeners))
+ for (ListIterator<HttpSessionListener> i = TypeUtil.listIteratorAtEnd(_sessionListeners); i.hasPrevious();)
  {
- listener.sessionDestroyed(event);
+ i.previous().sessionDestroyed(event);
  }
  };
  _contextHandler.getCoreContextHandler().getContext().run(r);