/**
    *
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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 org.apache.hadoop.hbase.mapred;
  
  import java.io.IOException;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.hbase.HBaseConfiguration;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.client.Connection;
  import org.apache.hadoop.hbase.client.ConnectionFactory;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.mapred.FileInputFormat;
  import org.apache.hadoop.mapred.JobConf;
  import org.apache.hadoop.mapred.JobConfigurable;
  import org.apache.hadoop.util.StringUtils;
  
  /**
   * Convert HBase tabular data into a format that is consumable by Map/Reduce.
   */
  @InterfaceAudience.Public
  @InterfaceStability.Stable
  public class TableInputFormat extends TableInputFormatBase implements
      JobConfigurable {
    private static final Log LOG = LogFactory.getLog(TableInputFormat.class);
  
    /**
     * space delimited list of columns
     */
    public static final String COLUMN_LIST = "hbase.mapred.tablecolumns";
  
    @Override
    public void configure(JobConf job) {
      try {
        initialize(job);
      } catch (Exception e) {
        LOG.error(StringUtils.stringifyException(e));
      }
    }
  
    @Override
    protected void initialize(JobConf job) throws IOException {
      Path[] tableNames = FileInputFormat.getInputPaths(job);
      String colArg = job.get(COLUMN_LIST);
      String[] colNames = colArg.split(" ");
      byte [][] m_cols = new byte[colNames.length][];
      for (int i = 0; i < m_cols.length; i++) {
        m_cols[i] = Bytes.toBytes(colNames[i]);
      }
      setInputColumns(m_cols);
      Connection connection = ConnectionFactory.createConnection(job);
      initializeTable(connection, TableName.valueOf(tableNames[0].getName()));
    }
  
    public void validateInput(JobConf job) throws IOException {
      // expecting exactly one path
      Path [] tableNames = FileInputFormat.getInputPaths(job);
      if (tableNames == null || tableNames.length > 1) {
        throw new IOException("expecting one table name");
      }
  
      // connected to table?
      if (getHTable() == null) {
        throw new IOException("could not connect to table '" +
          tableNames[0].getName() + "'");
      }
  
      // expecting at least one column
      String colArg = job.get(COLUMN_LIST);
      if (colArg == null || colArg.length() == 0) {
        throw new IOException("expecting at least one column");
      }
    }
  }