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Avoid list copy on reverse iteration #12297

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merged 3 commits into from
Sep 24, 2024
Merged

Avoid list copy on reverse iteration #12297

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6084705
Fix #12296 by partial revert of "Fixes #12289 - Improve ConcurrentPoo…
gregw Sep 23, 2024
47d5e0c
Fix #12296 by partial revert of "Fixes #12289 - Improve ConcurrentPoo…
gregw Sep 23, 2024
c2db17e
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gregw Sep 23, 2024
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4 changes: 2 additions & 2 deletions jetty-core/jetty-server/src/main/java/org/eclipse/jetty/server/handler/ContextHandler.java
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Original file line number Diff line number Diff line change
Expand Up @@ -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)
{
Expand Down
32 changes: 23 additions & 9 deletions jetty-core/jetty-util/src/main/java/org/eclipse/jetty/util/TypeUtil.java
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Expand Up @@ -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;
Expand Down Expand Up @@ -174,18 +175,31 @@ 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>
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* <p>The method is safe for concurrent modifications iff the list iterator itself is safe.</p>
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* @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.
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*/
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)
return Collections.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;
}
}

/**
Expand Down
17 changes: 9 additions & 8 deletions ...etty-ee10-servlet/src/main/java/org/eclipse/jetty/ee10/servlet/ServletContextHandler.java
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Expand Up @@ -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;
Expand Down Expand Up @@ -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)
{
Expand Down Expand Up @@ -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());
}
}
}
Expand Down Expand Up @@ -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)
{
Expand Down
5 changes: 3 additions & 2 deletions ...-ee10/jetty-ee10-servlet/src/main/java/org/eclipse/jetty/ee10/servlet/SessionHandler.java
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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);
}
});
}
Expand Down
13 changes: 7 additions & 6 deletions jetty-ee9/jetty-ee9-nested/src/main/java/org/eclipse/jetty/ee9/nested/ContextHandler.java
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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());
}
}
}
Expand Down Expand Up @@ -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)
{
Expand Down
5 changes: 3 additions & 2 deletions jetty-ee9/jetty-ee9-nested/src/main/java/org/eclipse/jetty/ee9/nested/SessionHandler.java
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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);
Expand Down
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