diff --git a/hugegraph-client/src/main/java/org/apache/hugegraph/serializer/AbstractGraphElementSerializer.java b/hugegraph-client/src/main/java/org/apache/hugegraph/serializer/AbstractGraphElementSerializer.java
index a5fed4bc7..bc2a4cbb9 100644
--- a/hugegraph-client/src/main/java/org/apache/hugegraph/serializer/AbstractGraphElementSerializer.java
+++ b/hugegraph-client/src/main/java/org/apache/hugegraph/serializer/AbstractGraphElementSerializer.java
@@ -1,3 +1,20 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to You under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+
 package org.apache.hugegraph.serializer;
 
 import org.apache.hugegraph.driver.HugeClient;
diff --git a/hugegraph-client/src/main/java/org/apache/hugegraph/serializer/GraphElementSerializer.java b/hugegraph-client/src/main/java/org/apache/hugegraph/serializer/GraphElementSerializer.java
index ba4fd538f..c55197386 100644
--- a/hugegraph-client/src/main/java/org/apache/hugegraph/serializer/GraphElementSerializer.java
+++ b/hugegraph-client/src/main/java/org/apache/hugegraph/serializer/GraphElementSerializer.java
@@ -1,3 +1,20 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to You under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+
 package org.apache.hugegraph.serializer;
 
 import org.apache.hugegraph.serializer.direct.struct.Directions;