fix channelHandlers has null object (#11357) (#11360)

dubbo-remoting/dubbo-remoting-api/src/main/java/org/apache/dubbo/remoting/transport/ChannelHandlerDispatcher.java

@@ -24,7 +24,9 @@ import org.apache.dubbo.remoting.ChannelHandler;
 
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Objects;
 import java.util.concurrent.CopyOnWriteArraySet;
+import java.util.stream.Collectors;
 
 import static org.apache.dubbo.common.constants.LoggerCodeConstants.INTERNAL_ERROR;
 
@@ -41,12 +43,15 @@ public class ChannelHandlerDispatcher implements ChannelHandler {
     }
 
     public ChannelHandlerDispatcher(ChannelHandler... handlers) {
+        // if varargs is used, the type of handlers is ChannelHandler[] and it is not null
+        // so we should filter the null object
         this(handlers == null ? null : Arrays.asList(handlers));
     }
 
     public ChannelHandlerDispatcher(Collection<ChannelHandler> handlers) {
         if (CollectionUtils.isNotEmpty(handlers)) {
-            this.channelHandlers.addAll(handlers);
+            // filter null object
+            this.channelHandlers.addAll(handlers.stream().filter(Objects::nonNull).collect(Collectors.toSet()));
         }
     }
 

dubbo-remoting/dubbo-remoting-api/src/test/java/org/apache/dubbo/remoting/transport/ChannelHandlerDispatcherTest.java

@@ -19,12 +19,13 @@ package org.apache.dubbo.remoting.transport;
 import org.apache.dubbo.remoting.Channel;
 import org.apache.dubbo.remoting.ChannelHandler;
 import org.apache.dubbo.remoting.RemotingException;
-
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 import org.mockito.Mockito;
 
 import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
 
 class ChannelHandlerDispatcherTest {
 
@@ -57,6 +58,23 @@ class ChannelHandlerDispatcherTest {
 
     }
 
+    @Test
+    void constructorNullObjectTest() {
+        ChannelHandlerDispatcher channelHandlerDispatcher = new ChannelHandlerDispatcher(null, null);
+        Assertions.assertEquals(0, channelHandlerDispatcher.getChannelHandlers().size());
+        ChannelHandlerDispatcher channelHandlerDispatcher1 = new ChannelHandlerDispatcher((MockChannelHandler) null);
+        Assertions.assertEquals(0, channelHandlerDispatcher1.getChannelHandlers().size());
+        ChannelHandlerDispatcher channelHandlerDispatcher2 = new ChannelHandlerDispatcher(null, new MockChannelHandler());
+        Assertions.assertEquals(1, channelHandlerDispatcher2.getChannelHandlers().size());
+        ChannelHandlerDispatcher channelHandlerDispatcher3 = new ChannelHandlerDispatcher(Collections.singleton(new MockChannelHandler()));
+        Assertions.assertEquals(1, channelHandlerDispatcher3.getChannelHandlers().size());
+        Collection<ChannelHandler> mockChannelHandlers = new HashSet<>();
+        mockChannelHandlers.add(new MockChannelHandler());
+        mockChannelHandlers.add(null);
+        ChannelHandlerDispatcher channelHandlerDispatcher4 = new ChannelHandlerDispatcher(mockChannelHandlers);
+        Assertions.assertEquals(1, channelHandlerDispatcher4.getChannelHandlers().size());
+    }
+
 }
 
 class MockChannelHandler extends ChannelHandlerAdapter {