content: /*
   * Copyright (C) 2010-2101 Alibaba Group Holding Limited.
   *
   * 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.otter.node.etl.common.io.download;
  
  import java.io.File;
  import java.io.IOException;
  import java.util.Observer;
  
  import com.alibaba.otter.node.etl.common.io.download.exception.DataRetrieveException;
  
  /**
   * 数据下载接口
   * 
   * @author brave.taoy
   */
  public interface DataRetriever {
  
      /**
       * This type of notification will be send if the progress changes.
       */
      public final static Integer NOTIFICATION_PROGRESS = 100;
  
      // control retriever
  
      /**
       * Advise the Retriever to connect to the data source.
       */
      public void connect() throws DataRetrieveException;
  
      /**
       * Do retrieve data
       */
      public void doRetrieve() throws DataRetrieveException;
  
      /**
       * Returns true if the data source contains any data to be read.
       */
      public boolean isDataAvailable() throws DataRetrieveException;
  
      /**
       * Returns an byte array for the retrieved data.
       */
      public byte[] getDataAsByteArray() throws DataRetrieveException;
  
      /**
       * Returns a file
       */
      public File getDataAsFile() throws DataRetrieveException;
  
      /**
       * Disconnect from the data source.
       */
      public void disconnect() throws DataRetrieveException;
  
      /**
       * Aborts the current retrieving.
       */
      public void abort();
  
      /**
       * Returns the content length in bytes.
       */
      public long getContentLength() throws IOException;
  
      public void addObserver(Observer o);
  }
  