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.nacos.api.selector;
  
  import com.alibaba.nacos.api.exception.NacosException;
  import com.alibaba.nacos.api.naming.pojo.Instance;
  import com.fasterxml.jackson.annotation.JsonTypeInfo;
  import com.fasterxml.jackson.annotation.JsonTypeInfo.Id;
  
  import java.io.Serializable;
  import java.util.List;
  
  /**
   * Abstract selector that only contains a type, used for api to set selector type without actual selector logic.
   *
   * @author nkorange
   * @since 0.7.0
   */
  @JsonTypeInfo(use = Id.NAME, property = "type", defaultImpl = NoneSelector.class)
  public abstract class AbstractSelector implements Serializable, Selector<List<Instance>, List<Instance>, String> {
      
      private static final long serialVersionUID = 4530233098102379229L;
      
      /**
       * The type of this selector, each child class should announce its own unique type.
       */
      private final String type;
      
      protected AbstractSelector(String type) {
          this.type = type;
      }
      
      public String getType() {
          return type;
      }
      
      @Override
      public Selector<List<Instance>, List<Instance>, String> parse(String expression) throws NacosException {
          return null;
      }
      
      @Override
      public List<Instance> select(List<Instance> context) {
          return context;
      }
      
      @Override
      public String getContextType() {
          return SelectorType.none.name();
      }
  }
  