content: /*
   * Copyright 1999-$toady.year 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.config.server.service.query;
  
  import com.alibaba.nacos.common.spi.NacosServiceLoader;
  import com.alibaba.nacos.config.server.exception.NacosConfigException;
  import com.alibaba.nacos.config.server.service.query.enums.ResponseCode;
  import com.alibaba.nacos.config.server.service.query.model.ConfigQueryChainRequest;
  import com.alibaba.nacos.config.server.service.query.model.ConfigQueryChainResponse;
  import com.alibaba.nacos.sys.env.EnvUtil;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.springframework.stereotype.Service;
  
  import java.util.Optional;
  
  /**
   * Service class for initializing and retrieving the configuration query chain builder.
   *
   * @author Nacos
   */
  @Service
  public class ConfigQueryChainService {
      
      private static final Logger LOGGER = LoggerFactory.getLogger(ConfigQueryChainService.class);
      
      private final ConfigQueryHandlerChain chain;
      
      public ConfigQueryChainService() {
          String curChain = EnvUtil.getProperty("nacos.config.query.chain.builder", "nacos");
          Optional<ConfigQueryHandlerChainBuilder> optionalBuilder = NacosServiceLoader.load(ConfigQueryHandlerChainBuilder.class)
                  .stream()
                  .filter(builder -> builder.getName().equals(curChain))
                  .findFirst();
          if (optionalBuilder.isPresent()) {
              chain = optionalBuilder.get().build();
              LOGGER.info("ConfigQueryHandlerChain has been initialized successfully with chain: {}", curChain);
          } else {
              String errorMessage = "No suitable ConfigQueryHandlerChainBuilder found for name: " + curChain;
              LOGGER.error(errorMessage);
              throw new NacosConfigException(errorMessage);
          }
      }
      
      /**
       * Handles the configuration query request.
       *
       * @param request the configuration query request object
       * @return the configuration query response object
       */
      public ConfigQueryChainResponse handle(ConfigQueryChainRequest request) {
          try {
              return chain.handle(request);
          } catch (Exception e) {
              LOGGER.error("[Error] Fail to handle ConfigQueryChainRequest", e);
              return ConfigQueryChainResponse.buildFailResponse(ResponseCode.FAIL.getCode(), e.getMessage());
          }
      }
  }