diff --git a/dubbo-all/pom.xml b/dubbo-all/pom.xml
index d8c8949c13e..eaa2dbc92ea 100644
--- a/dubbo-all/pom.xml
+++ b/dubbo-all/pom.xml
@@ -622,7 +622,7 @@
                                     <include>org.apache.dubbo:dubbo-serialization-jdk</include>
                                     <include>org.apache.dubbo:dubbo-serialization-protostuff</include>
                                     <include>org.apache.dubbo:dubbo-serialization-gson</include>
-                                    <include>org.apache.dubbo:dubbo-serialization-googlePb</include>
+                                    <include>org.apache.dubbo:dubbo-serialization-protobuf-json</include>
                                     <include>org.apache.dubbo:dubbo-configcenter-api</include>
                                     <include>org.apache.dubbo:dubbo-configcenter-definition</include>
                                     <include>org.apache.dubbo:dubbo-configcenter-apollo</include>
diff --git a/dubbo-common/src/main/java/org/apache/dubbo/common/beanutil/JavaBeanSerializeUtil.java b/dubbo-common/src/main/java/org/apache/dubbo/common/beanutil/JavaBeanSerializeUtil.java
index 995965ac74a..1ce5c455cf5 100644
--- a/dubbo-common/src/main/java/org/apache/dubbo/common/beanutil/JavaBeanSerializeUtil.java
+++ b/dubbo-common/src/main/java/org/apache/dubbo/common/beanutil/JavaBeanSerializeUtil.java
@@ -237,12 +237,12 @@ private static void deserializeInternal(Object result, JavaBeanDescriptor beanDe
             for (Map.Entry<Object, Object> entry : beanDescriptor) {
                 Object key = entry.getKey();
                 Object value = entry.getValue();
-                if (key != null && key instanceof JavaBeanDescriptor) {
+                if (key instanceof JavaBeanDescriptor) {
                     JavaBeanDescriptor keyDescriptor = (JavaBeanDescriptor) entry.getKey();
                     key = instantiateForDeserialize(keyDescriptor, loader, cache);
                     deserializeInternal(key, keyDescriptor, loader, cache);
                 }
-                if (value != null && value instanceof JavaBeanDescriptor) {
+                if (value instanceof JavaBeanDescriptor) {
                     JavaBeanDescriptor valueDescriptor = (JavaBeanDescriptor) entry.getValue();
                     value = instantiateForDeserialize(valueDescriptor, loader, cache);
                     deserializeInternal(value, valueDescriptor, loader, cache);
diff --git a/dubbo-common/src/main/java/org/apache/dubbo/common/json/JSONArray.java b/dubbo-common/src/main/java/org/apache/dubbo/common/json/JSONArray.java
index f5e039c3be8..a75bedbdd40 100644
--- a/dubbo-common/src/main/java/org/apache/dubbo/common/json/JSONArray.java
+++ b/dubbo-common/src/main/java/org/apache/dubbo/common/json/JSONArray.java
@@ -47,7 +47,7 @@ public Object get(int index) {
      */
     public boolean getBoolean(int index, boolean def) {
         Object tmp = mArray.get(index);
-        return tmp != null && tmp instanceof Boolean ? ((Boolean) tmp).booleanValue() : def;
+        return tmp instanceof Boolean ? ((Boolean) tmp).booleanValue() : def;
     }
 
     /**
@@ -59,7 +59,7 @@ public boolean getBoolean(int index, boolean def) {
      */
     public int getInt(int index, int def) {
         Object tmp = mArray.get(index);
-        return tmp != null && tmp instanceof Number ? ((Number) tmp).intValue() : def;
+        return tmp instanceof Number ? ((Number) tmp).intValue() : def;
     }
 
     /**
@@ -71,7 +71,7 @@ public int getInt(int index, int def) {
      */
     public long getLong(int index, long def) {
         Object tmp = mArray.get(index);
-        return tmp != null && tmp instanceof Number ? ((Number) tmp).longValue() : def;
+        return tmp instanceof Number ? ((Number) tmp).longValue() : def;
     }
 
     /**
@@ -83,7 +83,7 @@ public long getLong(int index, long def) {
      */
     public float getFloat(int index, float def) {
         Object tmp = mArray.get(index);
-        return tmp != null && tmp instanceof Number ? ((Number) tmp).floatValue() : def;
+        return tmp instanceof Number ? ((Number) tmp).floatValue() : def;
     }
 
     /**
@@ -95,7 +95,7 @@ public float getFloat(int index, float def) {
      */
     public double getDouble(int index, double def) {
         Object tmp = mArray.get(index);
-        return tmp != null && tmp instanceof Number ? ((Number) tmp).doubleValue() : def;
+        return tmp instanceof Number ? ((Number) tmp).doubleValue() : def;
     }
 
     /**
diff --git a/dubbo-common/src/main/java/org/apache/dubbo/common/json/JSONObject.java b/dubbo-common/src/main/java/org/apache/dubbo/common/json/JSONObject.java
index 052f35269dd..c04d4e14050 100644
--- a/dubbo-common/src/main/java/org/apache/dubbo/common/json/JSONObject.java
+++ b/dubbo-common/src/main/java/org/apache/dubbo/common/json/JSONObject.java
@@ -47,7 +47,7 @@ public Object get(String key) {
      */
     public boolean getBoolean(String key, boolean def) {
         Object tmp = mMap.get(key);
-        return tmp != null && tmp instanceof Boolean ? (Boolean) tmp : def;
+        return tmp instanceof Boolean ? (Boolean) tmp : def;
     }
 
     /**
@@ -59,7 +59,7 @@ public boolean getBoolean(String key, boolean def) {
      */
     public int getInt(String key, int def) {
         Object tmp = mMap.get(key);
-        return tmp != null && tmp instanceof Number ? ((Number) tmp).intValue() : def;
+        return tmp instanceof Number ? ((Number) tmp).intValue() : def;
     }
 
     /**
@@ -71,7 +71,7 @@ public int getInt(String key, int def) {
      */
     public long getLong(String key, long def) {
         Object tmp = mMap.get(key);
-        return tmp != null && tmp instanceof Number ? ((Number) tmp).longValue() : def;
+        return tmp instanceof Number ? ((Number) tmp).longValue() : def;
     }
 
     /**
@@ -83,7 +83,7 @@ public long getLong(String key, long def) {
      */
     public float getFloat(String key, float def) {
         Object tmp = mMap.get(key);
-        return tmp != null && tmp instanceof Number ? ((Number) tmp).floatValue() : def;
+        return tmp instanceof Number ? ((Number) tmp).floatValue() : def;
     }
 
     /**
@@ -95,7 +95,7 @@ public float getFloat(String key, float def) {
      */
     public double getDouble(String key, double def) {
         Object tmp = mMap.get(key);
-        return tmp != null && tmp instanceof Number ? ((Number) tmp).doubleValue() : def;
+        return tmp instanceof Number ? ((Number) tmp).doubleValue() : def;
     }
 
     /**
diff --git a/dubbo-common/src/main/java/org/apache/dubbo/common/utils/PojoUtils.java b/dubbo-common/src/main/java/org/apache/dubbo/common/utils/PojoUtils.java
index 3bab26134e3..52204acb4dd 100644
--- a/dubbo-common/src/main/java/org/apache/dubbo/common/utils/PojoUtils.java
+++ b/dubbo-common/src/main/java/org/apache/dubbo/common/utils/PojoUtils.java
@@ -366,7 +366,7 @@ private static Object realize0(Object pojo, Class<?> type, Type genericType, fin
                 history.put(pojo, dest);
                 for (Object obj : src) {
                     Type keyType = getGenericClassByIndex(genericType, 0);
-                    Class<?> keyClazz = obj.getClass();
+                    Class<?> keyClazz = obj == null ? null : obj.getClass();
                     if (keyType instanceof Class) {
                         keyClazz = (Class<?>) keyType;
                     }
diff --git a/dubbo-common/src/test/java/org/apache/dubbo/common/utils/PojoUtilsTest.java b/dubbo-common/src/test/java/org/apache/dubbo/common/utils/PojoUtilsTest.java
index 3595efb99f6..f0ab173b4f8 100644
--- a/dubbo-common/src/test/java/org/apache/dubbo/common/utils/PojoUtilsTest.java
+++ b/dubbo-common/src/test/java/org/apache/dubbo/common/utils/PojoUtilsTest.java
@@ -37,6 +37,7 @@
 import java.util.LinkedHashMap;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.HashSet;
 import java.util.Map;
 import java.util.UUID;
 
@@ -682,6 +683,24 @@ public void testDateTimeTimestamp() throws Exception {
         assertEquals(dateTimeStr, new SimpleDateFormat(dateFormat[0]).format(timestamp));
     }
 
+    @Test
+    public void testRealizeCollectionWithNullElement() {
+        LinkedList<String> listStr = new LinkedList<>();
+        listStr.add("arrayValue");
+        listStr.add(null);
+        HashSet<String> setStr = new HashSet<>();
+        setStr.add("setValue");
+        setStr.add(null);
+
+        Object listResult = PojoUtils.realize(listStr, LinkedList.class);
+        assertEquals(LinkedList.class, listResult.getClass());
+        assertEquals(listResult, listStr);
+
+        Object setResult = PojoUtils.realize(setStr, HashSet.class);
+        assertEquals(HashSet.class, setResult.getClass());
+        assertEquals(setResult, setStr);
+    }
+
     public enum Day {
         SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY
     }
diff --git a/dubbo-demo/dubbo-demo-annotation/dubbo-demo-annotation-consumer/pom.xml b/dubbo-demo/dubbo-demo-annotation/dubbo-demo-annotation-consumer/pom.xml
index c13bc265bc2..c8f9d9d50e1 100644
--- a/dubbo-demo/dubbo-demo-annotation/dubbo-demo-annotation-consumer/pom.xml
+++ b/dubbo-demo/dubbo-demo-annotation/dubbo-demo-annotation-consumer/pom.xml
@@ -42,6 +42,14 @@
             <groupId>org.apache.dubbo</groupId>
             <artifactId>dubbo-registry-multicast</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.apache.dubbo</groupId>
+            <artifactId>dubbo-registry-zookeeper</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.dubbo</groupId>
+            <artifactId>dubbo-configcenter-zookeeper</artifactId>
+        </dependency>
         <dependency>
             <groupId>org.apache.dubbo</groupId>
             <artifactId>dubbo-rpc-dubbo</artifactId>
diff --git a/dubbo-demo/dubbo-demo-annotation/dubbo-demo-annotation-provider/pom.xml b/dubbo-demo/dubbo-demo-annotation/dubbo-demo-annotation-provider/pom.xml
index 4f164bce61e..02d0248e431 100644
--- a/dubbo-demo/dubbo-demo-annotation/dubbo-demo-annotation-provider/pom.xml
+++ b/dubbo-demo/dubbo-demo-annotation/dubbo-demo-annotation-provider/pom.xml
@@ -43,6 +43,14 @@
             <groupId>org.apache.dubbo</groupId>
             <artifactId>dubbo-registry-multicast</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.apache.dubbo</groupId>
+            <artifactId>dubbo-registry-zookeeper</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.dubbo</groupId>
+            <artifactId>dubbo-configcenter-zookeeper</artifactId>
+        </dependency>
         <dependency>
             <groupId>org.apache.dubbo</groupId>
             <artifactId>dubbo-rpc-dubbo</artifactId>
diff --git a/dubbo-demo/dubbo-demo-xml/dubbo-demo-xml-consumer/pom.xml b/dubbo-demo/dubbo-demo-xml/dubbo-demo-xml-consumer/pom.xml
index 4dfde790cfa..5720551e7db 100644
--- a/dubbo-demo/dubbo-demo-xml/dubbo-demo-xml-consumer/pom.xml
+++ b/dubbo-demo/dubbo-demo-xml/dubbo-demo-xml-consumer/pom.xml
@@ -38,6 +38,14 @@
             <groupId>org.apache.dubbo</groupId>
             <artifactId>dubbo-registry-multicast</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.apache.dubbo</groupId>
+            <artifactId>dubbo-registry-zookeeper</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.dubbo</groupId>
+            <artifactId>dubbo-configcenter-zookeeper</artifactId>
+        </dependency>
         <dependency>
             <groupId>org.apache.dubbo</groupId>
             <artifactId>dubbo-config-spring</artifactId>
diff --git a/dubbo-demo/dubbo-demo-xml/dubbo-demo-xml-provider/pom.xml b/dubbo-demo/dubbo-demo-xml/dubbo-demo-xml-provider/pom.xml
index a93c41ccf00..c683235834a 100644
--- a/dubbo-demo/dubbo-demo-xml/dubbo-demo-xml-provider/pom.xml
+++ b/dubbo-demo/dubbo-demo-xml/dubbo-demo-xml-provider/pom.xml
@@ -40,6 +40,14 @@
             <groupId>org.apache.dubbo</groupId>
             <artifactId>dubbo-registry-multicast</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.apache.dubbo</groupId>
+            <artifactId>dubbo-registry-zookeeper</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.dubbo</groupId>
+            <artifactId>dubbo-configcenter-zookeeper</artifactId>
+        </dependency>
         <dependency>
             <groupId>org.apache.dubbo</groupId>
             <artifactId>dubbo-rpc-dubbo</artifactId>
diff --git a/dubbo-registry/dubbo-registry-api/src/main/java/org/apache/dubbo/registry/support/ProviderInvokerWrapper.java b/dubbo-registry/dubbo-registry-api/src/main/java/org/apache/dubbo/registry/support/ProviderInvokerWrapper.java
index ce079b743e4..a1eaad3410d 100644
--- a/dubbo-registry/dubbo-registry-api/src/main/java/org/apache/dubbo/registry/support/ProviderInvokerWrapper.java
+++ b/dubbo-registry/dubbo-registry-api/src/main/java/org/apache/dubbo/registry/support/ProviderInvokerWrapper.java
@@ -90,7 +90,7 @@ public void setReg(boolean reg) {
 
     @Override
     public boolean equals(Object o) {
-        if (o == null || !(o instanceof ProviderInvokerWrapper)) {
+        if (!(o instanceof ProviderInvokerWrapper)) {
             return false;
         }
         ProviderInvokerWrapper other = (ProviderInvokerWrapper) o;
diff --git a/dubbo-remoting/dubbo-remoting-netty/src/main/java/org/apache/dubbo/remoting/transport/netty/NettyHelper.java b/dubbo-remoting/dubbo-remoting-netty/src/main/java/org/apache/dubbo/remoting/transport/netty/NettyHelper.java
index ec73094ce95..64f41b2daef 100644
--- a/dubbo-remoting/dubbo-remoting-netty/src/main/java/org/apache/dubbo/remoting/transport/netty/NettyHelper.java
+++ b/dubbo-remoting/dubbo-remoting-netty/src/main/java/org/apache/dubbo/remoting/transport/netty/NettyHelper.java
@@ -27,7 +27,7 @@ final class NettyHelper {
 
     public static void setNettyLoggerFactory() {
         InternalLoggerFactory factory = InternalLoggerFactory.getDefaultFactory();
-        if (factory == null || !(factory instanceof DubboLoggerFactory)) {
+        if (!(factory instanceof DubboLoggerFactory)) {
             InternalLoggerFactory.setDefaultFactory(new DubboLoggerFactory());
         }
     }
diff --git a/dubbo-rpc/dubbo-rpc-dubbo/src/test/java/org/apache/dubbo/rpc/protocol/dubbo/decode/DubboTelnetDecodeTest.java b/dubbo-rpc/dubbo-rpc-dubbo/src/test/java/org/apache/dubbo/rpc/protocol/dubbo/decode/DubboTelnetDecodeTest.java
index e54d2e6508a..28c49cce497 100644
--- a/dubbo-rpc/dubbo-rpc-dubbo/src/test/java/org/apache/dubbo/rpc/protocol/dubbo/decode/DubboTelnetDecodeTest.java
+++ b/dubbo-rpc/dubbo-rpc-dubbo/src/test/java/org/apache/dubbo/rpc/protocol/dubbo/decode/DubboTelnetDecodeTest.java
@@ -452,7 +452,7 @@ private ByteBuf createDubboByteBuf() throws IOException {
     }
 
     private static boolean checkTelnetDecoded(Object msg) {
-        if (msg != null && msg instanceof String && !msg.toString().contains("Unsupported command:")) {
+        if (msg instanceof String && !msg.toString().contains("Unsupported command:")) {
             return true;
         }
         return false;