content: /*
   * Copyright 1999-2020 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.nacos.core.config;
  
  import com.alibaba.nacos.common.event.ServerConfigChangeEvent;
  import com.alibaba.nacos.common.notify.Event;
  import com.alibaba.nacos.common.notify.NotifyCenter;
  import com.alibaba.nacos.common.notify.listener.Subscriber;
  import com.alibaba.nacos.core.utils.Loggers;
  
  /**
   * Nacos abstract dynamic config.
   *
   * @author xiweng.yy
   */
  public abstract class AbstractDynamicConfig extends Subscriber<ServerConfigChangeEvent> {
      
      private final String configName;
      
      protected AbstractDynamicConfig(String configName) {
          this.configName = configName;
          NotifyCenter.registerSubscriber(this);
      }
      
      @Override
      public void onEvent(ServerConfigChangeEvent event) {
          resetConfig();
      }
      
      @Override
      public Class<? extends Event> subscribeType() {
          return ServerConfigChangeEvent.class;
      }
      
      protected void resetConfig() {
          try {
              getConfigFromEnv();
              Loggers.CORE.info("Get {} config from env, {}", configName, printConfig());
          } catch (Exception e) {
              Loggers.CORE.warn("Upgrade {} config from env failed, will use old value", configName, e);
          }
      }
      
      /**
       * Execute get config from env actually.
       */
      protected abstract void getConfigFromEnv();
      
      /**
       * Print config content.
       *
       * @return config content
       */
      protected abstract String printConfig();
  }
  