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.datasource;
  
  import com.alibaba.csp.sentinel.property.NoOpSentinelProperty;
  import com.alibaba.csp.sentinel.property.SentinelProperty;
  
  /**
   * A {@link ReadableDataSource} based on nothing. {@link EmptyDataSource#getProperty()} will always return the same cached
   * {@link SentinelProperty} that doing nothing.
   * <br/>
   * This class is used when we want to use default settings instead of configs from the {@link ReadableDataSource}.
   *
   * @author leyou
   */
  public final class EmptyDataSource implements ReadableDataSource<Object, Object> {
  
      public static final ReadableDataSource<Object, Object> EMPTY_DATASOURCE = new EmptyDataSource();
  
      private static final SentinelProperty<Object> PROPERTY = new NoOpSentinelProperty();
  
      private EmptyDataSource() { }
  
      @Override
      public Object loadConfig() throws Exception {
          return null;
      }
  
      @Override
      public Object readSource() throws Exception {
          return null;
      }
  
      @Override
      public SentinelProperty<Object> getProperty() {
          return PROPERTY;
      }
  
      @Override
      public void close() throws Exception { }
  }
  