From 6290fda4d3a794792dda75e0e4846a7c6c062a65 Mon Sep 17 00:00:00 2001
From: Sergey Rymsha <rymsha@yandex.ru>
Date: Thu, 10 Oct 2019 11:22:05 +0200
Subject: [PATCH] WebDispatcherImpl implementation issues #7523 keep elements
 with same order avoid copying on every dispatch

---
 .../web/impl/handler/WebDispatcherImpl.java   | 21 ++++++++++++-------
 .../impl/handler/WebDispatcherImplTest.java   | 14 +++++++++++++
 2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/modules/web/web-impl/src/main/java/com/enonic/xp/web/impl/handler/WebDispatcherImpl.java b/modules/web/web-impl/src/main/java/com/enonic/xp/web/impl/handler/WebDispatcherImpl.java
index 71ecb6ea80b..86e370d5afc 100644
--- a/modules/web/web-impl/src/main/java/com/enonic/xp/web/impl/handler/WebDispatcherImpl.java
+++ b/modules/web/web-impl/src/main/java/com/enonic/xp/web/impl/handler/WebDispatcherImpl.java
@@ -2,11 +2,14 @@
 
 import java.util.Comparator;
 import java.util.Iterator;
-import java.util.NavigableSet;
-import java.util.concurrent.ConcurrentSkipListSet;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Predicate;
+import java.util.stream.Stream;
 
 import org.osgi.service.component.annotations.Component;
 
+import com.google.common.collect.ImmutableList;
+
 import com.enonic.xp.web.WebRequest;
 import com.enonic.xp.web.WebResponse;
 import com.enonic.xp.web.handler.WebHandler;
@@ -16,18 +19,22 @@
 public final class WebDispatcherImpl
     implements WebDispatcher
 {
-    private final NavigableSet<WebHandler> webHandlerList = new ConcurrentSkipListSet<>( Comparator.comparingInt( WebHandler::getOrder ) );
+    private final AtomicReference<ImmutableList<WebHandler>> webHandlerListRef = new AtomicReference<>( ImmutableList.of() );
 
     @Override
     public void add( final WebHandler webHandler )
     {
-        this.webHandlerList.add( webHandler );
+        webHandlerListRef.updateAndGet( oldWebHandlers -> Stream.concat( oldWebHandlers.stream(), Stream.of( webHandler ) ).
+            sorted( Comparator.comparingInt( WebHandler::getOrder ) ).
+            collect( ImmutableList.toImmutableList() ) );
     }
 
     @Override
     public void remove( final WebHandler webHandler )
     {
-        this.webHandlerList.remove( webHandler );
+        webHandlerListRef.updateAndGet( oldWebHandlers -> oldWebHandlers.stream().filter( Predicate.not( w -> w != webHandler ) ).
+            sorted( Comparator.comparingInt( WebHandler::getOrder ) ).
+            collect( ImmutableList.toImmutableList() ) );
     }
 
     @Override
@@ -35,12 +42,12 @@ public WebResponse dispatch( final WebRequest req, final WebResponse res )
         throws Exception
     {
         ServletRequestHolder.setRequest( req.getRawRequest() );
-        return new WebHandlerChainImpl( this.webHandlerList ).handle( req, res );
+        return new WebHandlerChainImpl( this.webHandlerListRef.get() ).handle( req, res );
     }
 
     @Override
     public Iterator<WebHandler> iterator()
     {
-        return this.webHandlerList.iterator();
+        return this.webHandlerListRef.get().iterator();
     }
 }
diff --git a/modules/web/web-impl/src/test/java/com/enonic/xp/web/impl/handler/WebDispatcherImplTest.java b/modules/web/web-impl/src/test/java/com/enonic/xp/web/impl/handler/WebDispatcherImplTest.java
index eb6617b2112..c33119130be 100644
--- a/modules/web/web-impl/src/test/java/com/enonic/xp/web/impl/handler/WebDispatcherImplTest.java
+++ b/modules/web/web-impl/src/test/java/com/enonic/xp/web/impl/handler/WebDispatcherImplTest.java
@@ -31,4 +31,18 @@ void orderedProperly()
         assertSame( webHandler1, list.get( 2 ) );
         assertSame( webHandlerMax, list.get( 3 ) );
     }
+
+    @Test
+    void supportsEqualOderElements()
+    {
+        final WebDispatcherImpl dispatcher = new WebDispatcherImpl();
+        TestWebHandler webHandler0 = new TestWebHandler( 0 );
+        dispatcher.add( webHandler0 );
+        TestWebHandler webHandlerAlso0 = new TestWebHandler( 0 );
+        dispatcher.add( webHandlerAlso0 );
+
+        List<WebHandler> list = StreamSupport.stream( dispatcher.spliterator(), false ).collect( Collectors.toList() );
+        assertSame( webHandler0, list.get( 0 ) );
+        assertSame( webHandlerAlso0, list.get( 1 ) );
+    }
 }