style: 添加 NoneListener 注释。

mybatis-flex-annotation/src/main/java/com/mybatisflex/annotation/NoneListener.java

@@ -1,4 +1,4 @@
-/**
+/*
  *  Copyright (c) 2022-2023, Mybatis-Flex (fuhai999@gmail.com).
  *  <p>
  *  Licensed under the Apache License, Version 2.0 (the "License");
@@ -15,19 +15,24 @@
  */
 package com.mybatisflex.annotation;
 
+/**
+ * 空监听器。
+ */
 public final class NoneListener implements InsertListener, UpdateListener, SetListener {
+
     @Override
     public void onInsert(Object entity) {
-
+        // do nothing here.
     }
 
     @Override
     public void onUpdate(Object entity) {
-
+        // do nothing here.
     }
 
     @Override
     public Object onSet(Object entity, String property, Object value) {
         return value;
     }
+
 }