content: /*
   * Copyright 1999-2018 Alibaba Group Holding Ltd.
   *
   * Licensed 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 com.alibaba.csp.sentinel.property;
  
  import com.alibaba.csp.sentinel.log.RecordLog;
  
  import java.util.Set;
  import java.util.concurrent.CopyOnWriteArraySet;
  
  public class DynamicSentinelProperty<T> implements SentinelProperty<T> {
  
      protected Set<PropertyListener<T>> listeners = new CopyOnWriteArraySet<>();
      private T value = null;
  
      public DynamicSentinelProperty() {
      }
  
      public DynamicSentinelProperty(T value) {
          super();
          this.value = value;
      }
  
      @Override
      public void addListener(PropertyListener<T> listener) {
          listeners.add(listener);
          listener.configLoad(value);
      }
  
      @Override
      public void removeListener(PropertyListener<T> listener) {
          listeners.remove(listener);
      }
  
      @Override
      public boolean updateValue(T newValue) {
          if (isEqual(value, newValue)) {
              return false;
          }
          RecordLog.info("[DynamicSentinelProperty] Config will be updated to: {}", newValue);
  
          value = newValue;
          for (PropertyListener<T> listener : listeners) {
              listener.configUpdate(newValue);
          }
          return true;
      }
  
      private boolean isEqual(T oldValue, T newValue) {
          if (oldValue == null && newValue == null) {
              return true;
          }
  
          if (oldValue == null) {
              return false;
          }
  
          return oldValue.equals(newValue);
      }
  
      public void close() {
          listeners.clear();
      }
  }
  