From cb576d16e11b838095c81d9a9698ed0373752a91 Mon Sep 17 00:00:00 2001
From: Rob Winch <rwinch@users.noreply.github.com>
Date: Tue, 24 Oct 2017 15:35:04 -0500
Subject: [PATCH] DelegatingApplicationListener uses CopyOnWriteArrayList

Fixes gh-4417
---
 .../security/context/DelegatingApplicationListener.java       | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/core/src/main/java/org/springframework/security/context/DelegatingApplicationListener.java b/core/src/main/java/org/springframework/security/context/DelegatingApplicationListener.java
index bfe0cb5508..52d1733792 100644
--- a/core/src/main/java/org/springframework/security/context/DelegatingApplicationListener.java
+++ b/core/src/main/java/org/springframework/security/context/DelegatingApplicationListener.java
@@ -20,8 +20,8 @@ import org.springframework.context.ApplicationListener;
 import org.springframework.context.event.SmartApplicationListener;
 import org.springframework.util.Assert;
 
-import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
 
 /**
  * Used for delegating to a number of SmartApplicationListener instances. This is useful
@@ -32,7 +32,7 @@ import java.util.List;
  */
 public final class DelegatingApplicationListener implements
 		ApplicationListener<ApplicationEvent> {
-	private List<SmartApplicationListener> listeners = new ArrayList<SmartApplicationListener>();
+	private List<SmartApplicationListener> listeners = new CopyOnWriteArrayList<SmartApplicationListener>();
 
 	public void onApplicationEvent(ApplicationEvent event) {
 		if (event == null) {