From 565557c5c5b5d22cbcedfdcdad4289e5a4461a96 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=9D=A8=E7=BF=8A=20SionYang?= <263976490@qq.com>
Date: Tue, 15 Sep 2020 14:50:57 +0800
Subject: [PATCH] Fix NullPointerException when no subscriber for slow event
 (#3835)

---
 .../alibaba/nacos/common/notify/DefaultSharePublisher.java    | 4 ++++
 .../com/alibaba/nacos/common/notify/NotifyCenterTest.java     | 1 +
 2 files changed, 5 insertions(+)

diff --git a/common/src/main/java/com/alibaba/nacos/common/notify/DefaultSharePublisher.java b/common/src/main/java/com/alibaba/nacos/common/notify/DefaultSharePublisher.java
index 3028423f7..a2fa996d1 100644
--- a/common/src/main/java/com/alibaba/nacos/common/notify/DefaultSharePublisher.java
+++ b/common/src/main/java/com/alibaba/nacos/common/notify/DefaultSharePublisher.java
@@ -96,6 +96,10 @@ public class DefaultSharePublisher extends DefaultPublisher {
         
         // Get for Map, the algorithm is O(1).
         Set<Subscriber> subscribers = subMappings.get(slowEventType);
+        if (null == subscribers) {
+            LOGGER.debug("[NotifyCenter] No subscribers for slow event {}", slowEventType.getName());
+            return;
+        }
         
         // Notification single event subscriber
         for (Subscriber subscriber : subscribers) {
diff --git a/common/src/test/java/com/alibaba/nacos/common/notify/NotifyCenterTest.java b/common/src/test/java/com/alibaba/nacos/common/notify/NotifyCenterTest.java
index a7163938d..d1abd7c1e 100644
--- a/common/src/test/java/com/alibaba/nacos/common/notify/NotifyCenterTest.java
+++ b/common/src/test/java/com/alibaba/nacos/common/notify/NotifyCenterTest.java
@@ -132,6 +132,7 @@ public class NotifyCenterTest {
                 return ExpireEvent.class;
             }
             
+            @Override
             public boolean ignoreExpireEvent() {
                 return true;
             }