[ISSUE#3356]fix no throw exception when publish event but no subscibe…

…r. (alibaba#3363)

common/src/main/java/com/alibaba/nacos/common/notify/NotifyCenter.java

@@ -290,7 +290,9 @@ private static boolean publishEvent(final Class<? extends Event> eventType, fina
             EventPublisher publisher = INSTANCE.publisherMap.get(topic);
             return publisher.publish(event);
         }
-        throw new NoSuchElementException("There are no [" + topic + "] publishers for this event, please register");
+
+        LOGGER.warn("There are no [{}] publishers for this event, please register", topic);
+        return false;
     }
 
     /**

common/src/test/java/com/alibaba/nacos/common/notify/NotifyCenterTest.java

@@ -35,6 +35,7 @@
 public class NotifyCenterTest {
 
     private static class TestSlowEvent extends SlowEvent {
+
     }
 
     private static class TestEvent extends Event {
@@ -330,9 +331,11 @@ public void onEvent(Event event) {
     }
 
     private static class TestSlowEvent1 extends SlowEvent {
+
     }
 
     private static class TestSlowEvent2 extends SlowEvent {
+
     }
 
     @Test
@@ -343,10 +346,10 @@ public void testMutipleSlowEventsListenedBySubscriber() throws Exception {
 
         final AtomicInteger count1 = new AtomicInteger(0);
         final AtomicInteger count2 = new AtomicInteger(0);
-
+        
         final CountDownLatch latch1 = new CountDownLatch(3);
         final CountDownLatch latch2 = new CountDownLatch(3);
-
+        
         NotifyCenter.registerSubscriber(new Subscriber<TestSlowEvent1>() {
             @Override
             public void onEvent(TestSlowEvent1 event) {
@@ -365,34 +368,36 @@ public Class<? extends Event> subscribeType() {
             public void onEvent(TestSlowEvent2 event) {
                 count2.incrementAndGet();
                 latch2.countDown();
-
+                
             }
 
             @Override
             public Class<? extends Event> subscribeType() {
                 return TestSlowEvent2.class;
             }
         });
-
+        
         for (int i = 0; i < 3; i++) {
             Assert.assertTrue(NotifyCenter.publishEvent(new TestSlowEvent1()));
             Assert.assertTrue(NotifyCenter.publishEvent(new TestSlowEvent2()));
         }
-
+        
         ThreadUtils.sleep(2000L);
-
+        
         latch1.await(3000L, TimeUnit.MILLISECONDS);
         latch2.await(3000L, TimeUnit.MILLISECONDS);
-
+        
         Assert.assertEquals(3, count1.get());
         Assert.assertEquals(3, count2.get());
-
+        
     }
 
     private static class TestSlowEvent3 extends SlowEvent {
+
     }
 
     private static class TestSlowEvent4 extends SlowEvent {
+
     }
 
     @Test
@@ -408,7 +413,7 @@ public void testMutipleSlowEventsListenedBySmartsubscriber() throws Exception {
         final CountDownLatch latch2 = new CountDownLatch(3);
 
         NotifyCenter.registerSubscriber(new SmartSubscriber() {
-
+            
             @Override
             public void onEvent(Event event) {
                 if (event instanceof TestSlowEvent3) {
@@ -421,7 +426,7 @@ public void onEvent(Event event) {
                     latch2.countDown();
                 }
             }
-
+            
             @Override
             public List<Class<? extends Event>> subscribeTypes() {
                 List<Class<? extends Event>> subTypes = new ArrayList<Class<? extends Event>>();
@@ -447,9 +452,11 @@ public List<Class<? extends Event>> subscribeTypes() {
     }
 
     private static class TestSlowEvent5 extends SlowEvent {
+
     }
 
     private static class TestEvent6 extends Event {
+
     }
 
     @Test
@@ -502,4 +509,16 @@ public List<Class<? extends Event>> subscribeTypes() {
         Assert.assertEquals(3, count2.get());
 
     }
+
+    private static class TestEvent7 extends Event {
+
+    }
+
+    @Test
+    public void testPublishEventByNoSubscriber() {
+
+        for (int i = 0; i < 3; i++) {
+            Assert.assertFalse(NotifyCenter.publishEvent(new TestEvent7()));
+        }
+    }
 }