Java tutorial
/** * Copyright 2009 The Apache Software Foundation * * 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 com.lakala.hbase; import java.io.ByteArrayOutputStream; import java.io.DataOutputStream; import java.io.IOException; import java.util.HashMap; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.hbase.HBaseConfiguration; import org.apache.hadoop.hbase.client.Put; import org.apache.hadoop.hbase.client.Result; import org.apache.hadoop.hbase.client.Scan; import org.apache.hadoop.hbase.io.ImmutableBytesWritable; import org.apache.hadoop.hbase.mapreduce.MultiTableOutputFormat; import org.apache.hadoop.hbase.mapreduce.TableInputFormat; import org.apache.hadoop.hbase.mapreduce.TableMapReduceUtil; import org.apache.hadoop.hbase.util.Base64; import org.apache.hadoop.hbase.util.Bytes; import org.apache.hadoop.io.Writable; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.Mapper; import org.apache.hadoop.util.GenericOptionsParser; /** * Example map/reduce job to construct index tables that can be used to quickly * find a row based on the value of a column. It demonstrates: * <ul> * <li>Using TableInputFormat and TableMapReduceUtil to use an HTable as input to a map/reduce job.</li> * <li>Passing values from main method to children via the configuration.</li> * <li>Using MultiTableOutputFormat to output to multiple tables from a map/reduce job.</li> * <li>A real use case of building a secondary index over a table.</li> * </ul> * * <h3>Usage</h3> * * <p> * Modify ${HADOOP_HOME}/conf/hadoop-env.sh to include the hbase jar, the zookeeper jar, the examples output directory, and the * hbase conf directory in HADOOP_CLASSPATH, and then run * <tt><strong>bin/hadoop org.apache.hadoop.hbase.mapreduce.IndexBuilder TABLE_NAME COLUMN_FAMILY ATTR [ATTR ...]</strong></tt> * </p> * * <p> * To run with the sample data provided in index-builder-setup.rb, use the arguments <strong> * <tt>people attributes name email phone</tt></strong>. * </p> * * <p> * This code was written against HBase 0.21 trunk. * </p> */ public class IndexBuilder2 { /** the column family containing the indexed row key */ public static final byte[] INDEX_COLUMN = Bytes.toBytes("INDEX"); /** the qualifier containing the indexed row key */ public static final byte[] INDEX_QUALIFIER = Bytes.toBytes("ROW"); /** * Internal Mapper to be run by Hadoop. */ public static class Map extends Mapper<ImmutableBytesWritable, Result, ImmutableBytesWritable, Writable> { private byte[] family; private HashMap<byte[], ImmutableBytesWritable> indexes; @Override protected void map(ImmutableBytesWritable rowKey, Result result, Context context) throws IOException, InterruptedException { for (java.util.Map.Entry<byte[], ImmutableBytesWritable> index : indexes.entrySet()) { byte[] qualifier = index.getKey(); ImmutableBytesWritable tableName = index.getValue(); byte[] value = result.getValue(family, qualifier); if (value != null) { // original: row 123 attribute:phone 555-1212 // index: row 555-1212 INDEX:ROW 123 Put put = new Put(value); put.add(INDEX_COLUMN, INDEX_QUALIFIER, rowKey.get()); context.write(tableName, put); } } } @Override protected void setup(Context context) throws IOException, InterruptedException { Configuration configuration = context.getConfiguration(); String tableName = configuration.get("index.tablename"); String[] fields = configuration.getStrings("index.fields"); String familyName = configuration.get("index.familyname"); family = Bytes.toBytes(familyName); indexes = new HashMap<byte[], ImmutableBytesWritable>(); for (String field : fields) { // if the table is "people" and the field to index is "email", then the // index table will be called "people-email" indexes.put(Bytes.toBytes(field), new ImmutableBytesWritable(Bytes.toBytes(tableName + "-" + field))); } } } static String convertScanToString(Scan scan) throws IOException { ByteArrayOutputStream out = new ByteArrayOutputStream(); DataOutputStream dos = new DataOutputStream(out); scan.write(dos); return Base64.encodeBytes(out.toByteArray()); } /** * Job configuration. */ public static Job configureJob(Configuration conf, String[] args) throws IOException { String tableName = args[0]; String columnFamily = args[1]; System.out.println("****" + tableName); conf.set(TableInputFormat.SCAN, convertScanToString(new Scan())); conf.set(TableInputFormat.INPUT_TABLE, tableName); conf.set("index.tablename", tableName); conf.set("index.familyname", columnFamily); String[] fields = new String[args.length - 2]; for (int i = 0; i < fields.length; i++) { fields[i] = args[i + 2]; } conf.setStrings("index.fields", fields); conf.set("index.familyname", "attributes"); Job job = new Job(conf, tableName); job.setJarByClass(IndexBuilder.class); job.setMapperClass(Map.class); job.setNumReduceTasks(0); job.setInputFormatClass(TableInputFormat.class); job.setOutputFormatClass(MultiTableOutputFormat.class); return job; } public static void main(String[] args) throws Exception { Configuration conf = HBaseConfiguration.create(); String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs(); if (otherArgs.length < 3) { System.err.println("Only " + otherArgs.length + " arguments supplied, required: 3"); System.err.println("Usage: IndexBuilder <TABLE_NAME> <COLUMN_FAMILY> <ATTR> [<ATTR> ...]"); System.exit(-1); } Job job = configureJob(conf, otherArgs); System.exit(job.waitForCompletion(true) ? 0 : 1); } }