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Simple Apache Accumulo examples.
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/*
 * 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.accumulo.examples.simple.mapreduce;

import java.io.IOException;
import java.util.AbstractMap.SimpleImmutableEntry;
import java.util.HashSet;
import java.util.Map;

import org.apache.accumulo.core.cli.MapReduceClientOnRequiredTable;
import org.apache.accumulo.core.client.AccumuloSecurityException;
import org.apache.accumulo.core.client.mapreduce.AccumuloInputFormat;
import org.apache.accumulo.core.data.Key;
import org.apache.accumulo.core.data.Value;
import org.apache.accumulo.core.util.Pair;
import org.apache.accumulo.core.util.format.DefaultFormatter;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

import com.beust.jcommander.Parameter;

/**
 * Takes a table and outputs the specified column to a set of part files on hdfs
 *
 * 
 * CLI options (in order):
 * 

 * username
 * 
password
 * 
tablename
 * 
column
 * 
hdfs-output-path
 * 
 */
public class TableToFile extends Configured implements Tool {

  static class Opts extends MapReduceClientOnRequiredTable {
    @Parameter(names = "--output", description = "output directory", required = true)
    String output;
    @Parameter(names = "--columns", description = "columns to extract, in cf:cq{,cf:cq,...} form")
    String columns = "";
  }

  /**
   * The Mapper class that given a row number, will generate the appropriate output line.
   */
  public static class TTFMapper extends Mapper {
    @Override
    public void map(Key row, Value data, Context context) throws IOException, InterruptedException {
      Map.Entry entry = new SimpleImmutableEntry<>(row, data);
      context.write(NullWritable.get(), new Text(DefaultFormatter.formatEntry(entry, false)));
      context.setStatus("Outputed Value");
    }
  }

  @Override
  public int run(String[] args)
      throws IOException, InterruptedException, ClassNotFoundException, AccumuloSecurityException {
    Job job = Job.getInstance(getConf());
    job.setJobName(this.getClass().getSimpleName() + "_" + System.currentTimeMillis());
    job.setJarByClass(this.getClass());
    Opts opts = new Opts();
    opts.parseArgs(getClass().getName(), args);

    job.setInputFormatClass(AccumuloInputFormat.class);
    opts.setAccumuloConfigs(job);

    HashSet> columnsToFetch = new HashSet<>();
    for (String col : opts.columns.split(",")) {
      int idx = col.indexOf(":");
      Text cf = new Text(idx < 0 ? col : col.substring(0, idx));
      Text cq = idx < 0 ? null : new Text(col.substring(idx + 1));
      if (cf.getLength() > 0)
        columnsToFetch.add(new Pair<>(cf, cq));
    }
    if (!columnsToFetch.isEmpty())
      AccumuloInputFormat.fetchColumns(job, columnsToFetch);

    job.setMapperClass(TTFMapper.class);
    job.setMapOutputKeyClass(NullWritable.class);
    job.setMapOutputValueClass(Text.class);

    job.setNumReduceTasks(0);

    job.setOutputFormatClass(TextOutputFormat.class);
    TextOutputFormat.setOutputPath(job, new Path(opts.output));

    job.waitForCompletion(true);
    return job.isSuccessful() ? 0 : 1;
  }

  /**
   *
   * @param args
   *          instanceName zookeepers username password table columns outputpath
   */
  public static void main(String[] args) throws Exception {
    ToolRunner.run(new Configuration(), new TableToFile(), args);
  }
}