版權聲明:本文為部落客原創文章,未經部落客允許不得轉載。 https://blog.csdn.net/SunnyYoona/article/details/53486203
FileOutputFormat及其子類産生的檔案放在輸出目錄下。每個reducer一個檔案并且檔案由分區号命名:part-r-00000,part-r-00001,等等。有時可能要對輸出的檔案名進行控制或讓每個reducer輸出多個檔案。MapReduce為此提供了MultipleOutputFormat類。
MultipleOutputFormat類可以将資料寫到多個檔案,這些檔案的名稱源于輸出的鍵和值或者任意字元串。這允許每個reducer(或者隻有map作業的mapper)建立多個檔案。采用name-r-nnnnn形式的檔案名用于map輸出,name-r-nnnnn形式的檔案名用于reduce輸出,其中name是由程式設定的任意名字,nnnnn是一個指名塊号的整數(從0開始)。塊号保證從不同塊(mapper或者reducer)寫的輸出在相同名字情況下不會沖突。
1. 重定義輸出檔案名
我們可以對輸出的檔案名進行控制。考慮這樣一個需求:按男女性别來區分度假訂單資料。這需要運作一個作業,作業的輸出是男女各一個檔案,此檔案包含男女性别的所有資料記錄。
這個需求可以使用MultipleOutputs來實作:
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package com.sjf.open.test;
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import java.io.IOException;
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import org.apache.commons.lang3.StringUtils;
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import org.apache.hadoop.conf.Configuration;
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import org.apache.hadoop.conf.Configured;
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import org.apache.hadoop.fs.Path;
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import org.apache.hadoop.io.LongWritable;
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import org.apache.hadoop.io.NullWritable;
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import org.apache.hadoop.io.Text;
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import org.apache.hadoop.io.compress.CompressionCodec;
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import org.apache.hadoop.io.compress.GzipCodec;
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import org.apache.hadoop.mapred.JobPriority;
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import org.apache.hadoop.mapreduce.Job;
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import org.apache.hadoop.mapreduce.Mapper;
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import org.apache.hadoop.mapreduce.Reducer;
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import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
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import org.apache.hadoop.mapreduce.lib.input.FileSplit;
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import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
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import org.apache.hadoop.mapreduce.lib.output.MultipleOutputs;
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import org.apache.hadoop.util.Tool;
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import org.apache.hadoop.util.ToolRunner;
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import com.sjf.open.utils.ConfigUtil;
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/**
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* Created by xiaosi on 16-11-7.
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*/
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public class VacationOrderBySex extends Configured implements Tool {
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public static void main(String[] args) throws Exception {
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int status = ToolRunner.run(new VacationOrderBySex(), args);
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System.exit(status);
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}
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public static class VacationOrderBySexMapper extends Mapper<LongWritable, Text, Text, Text> {
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public String fInputPath = "";
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@Override
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protected void setup(Context context) throws IOException, InterruptedException {
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super.setup(context);
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fInputPath = ((FileSplit) context.getInputSplit()).getPath().toString();
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}
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@Override
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protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
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String line = value.toString();
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if(fInputPath.contains("vacation_hot_country_order")){
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String[] params = line.split("\t");
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String sex = params[2];
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if(StringUtils.isBlank(sex)){
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return;
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}
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context.write(new Text(sex.toLowerCase()), value);
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}
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}
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}
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public static class VacationOrderBySexReducer extends Reducer<Text, Text, NullWritable, Text> {
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private MultipleOutputs<NullWritable, Text> multipleOutputs;
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@Override
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protected void setup(Context context) throws IOException, InterruptedException {
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multipleOutputs = new MultipleOutputs<NullWritable, Text>(context);
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}
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@Override
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protected void reduce(Text key, Iterable<Text> values, Context context)
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throws IOException, InterruptedException {
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for (Text value : values) {
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multipleOutputs.write(NullWritable.get(), value, key.toString());
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}
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}
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@Override
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protected void cleanup(Context context) throws IOException, InterruptedException {
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multipleOutputs.close();
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}
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}
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@Override
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public int run(String[] args) throws Exception {
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if (args.length != 2) {
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System.err.println("./run <input> <output>");
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System.exit(1);
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}
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String inputPath = args[0];
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String outputPath = args[1];
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int numReduceTasks = 16;
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Configuration conf = this.getConf();
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conf.setBoolean("mapred.output.compress", true);
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conf.setClass("mapred.output.compression.codec", GzipCodec.class, CompressionCodec.class);
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Job job = Job.getInstance(conf);
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job.setJobName("vacation_order_by_jifeng.si");
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job.setJarByClass(VacationOrderBySex.class);
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job.setMapperClass(VacationOrderBySexMapper.class);
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job.setReducerClass(VacationOrderBySexReducer.class);
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job.setMapOutputKeyClass(Text.class);
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job.setMapOutputValueClass(Text.class);
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job.setOutputKeyClass(NullWritable.class);
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job.setOutputValueClass(Text.class);
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FileInputFormat.setInputPaths(job, inputPath);
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FileOutputFormat.setOutputPath(job, new Path(outputPath));
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job.setNumReduceTasks(numReduceTasks);
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boolean success = job.waitForCompletion(true);
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return success ? 0 : 1;
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}
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}
在生成輸出的reduce中,在setup()方法中構造一個MultipleOutputs的執行個體并将它賦予一個執行個體變量。在reduce()方法中使用MultipleOutputs執行個體來寫輸出,而不是context。write()方法作用于鍵,值和名字。這裡使用的是性别作為名字,是以最後産生的輸出名稱的形式為sex-r-nnnnn:
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-rw-r--r-- 3 wirelessdev wirelessdev 0 2016-12-06 10:41 tmp/data_group/order/vacation_hot_country_order_by_sex/_SUCCESS
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-rw-r--r-- 3 wirelessdev wirelessdev 88574 2016-12-06 10:41 tmp/data_group/order/vacation_hot_country_order_by_sex/f-r-00005.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 60965 2016-12-06 10:41 tmp/data_group/order/vacation_hot_country_order_by_sex/m-r-00012.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 20 2016-12-06 10:41 tmp/data_group/order/vacation_hot_country_order_by_sex/part-r-00000.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 20 2016-12-06 10:41 tmp/data_group/order/vacation_hot_country_order_by_sex/part-r-00001.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 20 2016-12-06 10:41 tmp/data_group/order/vacation_hot_country_order_by_sex/part-r-00002.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 20 2016-12-06 10:41 tmp/data_group/order/vacation_hot_country_order_by_sex/part-r-00003.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 20 2016-12-06 10:41 tmp/data_group/order/vacation_hot_country_order_by_sex/part-r-00004.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 20 2016-12-06 10:41 tmp/data_group/order/vacation_hot_country_order_by_sex/part-r-00005.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 20 2016-12-06 10:41 tmp/data_group/order/vacation_hot_country_order_by_sex/part-r-00006.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 20 2016-12-06 10:41 tmp/data_group/order/vacation_hot_country_order_by_sex/part-r-00007.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 20 2016-12-06 10:41 tmp/data_group/order/vacation_hot_country_order_by_sex/part-r-00008.gz
我們可以看到在輸出檔案中不僅有我們想要的輸出檔案類型,還有part-r-nnnnn形式的檔案,但是檔案内沒有資訊,這是程式預設的輸出檔案。是以我們在指定輸出檔案名稱時(name-r-nnnnn),不要指定name為part,因為它已經被使用為預設值了。
2. 多目錄輸出
在MultipleOutputs的write()方法中指定的基本路徑相對于輸出路徑進行解釋,因為它可以包含檔案路徑分隔符(/),建立任意深度的子目錄。例如,我們改動上面的需求:按男女性别來區分度假訂單資料,不同性别資料位于不同子目錄(例如:sex=f/part-r-00000)。
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public static class VacationOrderBySexReducer extends Reducer<Text, Text, NullWritable, Text> {
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private MultipleOutputs<NullWritable, Text> multipleOutputs;
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@Override
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protected void setup(Context context) throws IOException, InterruptedException {
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multipleOutputs = new MultipleOutputs<NullWritable, Text>(context);
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}
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@Override
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protected void reduce(Text key, Iterable<Text> values, Context context)
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throws IOException, InterruptedException {
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for (Text value : values) {
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String basePath = String.format("sex=%s/part", key.toString());
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multipleOutputs.write(NullWritable.get(), value, basePath);
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}
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}
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@Override
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protected void cleanup(Context context) throws IOException, InterruptedException {
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multipleOutputs.close();
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}
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}
後産生的輸出名稱的形式為sex=f/part-r-nnnnn或者sex=m/part-r-nnnnn:
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-rw-r--r-- 3 wirelessdev wirelessdev 0 2016-12-06 12:26 tmp/data_group/order/vacation_hot_country_order_by_sex/_SUCCESS
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-rw-r--r-- 3 wirelessdev wirelessdev 20 2016-12-06 12:26 tmp/data_group/order/vacation_hot_country_order_by_sex/part-r-00000.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 20 2016-12-06 12:26 tmp/data_group/order/vacation_hot_country_order_by_sex/part-r-00001.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 20 2016-12-06 12:26 tmp/data_group/order/vacation_hot_country_order_by_sex/part-r-00002.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 20 2016-12-06 12:26 tmp/data_group/order/vacation_hot_country_order_by_sex/part-r-00003.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 20 2016-12-06 12:26 tmp/data_group/order/vacation_hot_country_order_by_sex/part-r-00004.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 20 2016-12-06 12:26 tmp/data_group/order/vacation_hot_country_order_by_sex/part-r-00005.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 20 2016-12-06 12:26 tmp/data_group/order/vacation_hot_country_order_by_sex/part-r-00006.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 20 2016-12-06 12:26 tmp/data_group/order/vacation_hot_country_order_by_sex/part-r-00007.gz
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drwxr-xr-x - wirelessdev wirelessdev 0 2016-12-06 12:26 tmp/data_group/order/vacation_hot_country_order_by_sex/sex=f
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drwxr-xr-x - wirelessdev wirelessdev 0 2016-12-06 12:26 tmp/data_group/order/vacation_hot_country_order_by_sex/sex=m
3. 延遲輸出
FileOutputFormat的子類會産生輸出檔案(part-r-nnnnn),即使檔案是空的,也會産生。我們有時候不想要這些空的檔案,我們可以使用LazyOutputFormat進行處理。它是一個封裝輸出格式,可以指定分區第一條記錄輸出時才真正建立檔案。要使用它,用JobConf和相關輸出格式作為參數來調用setOutputFormatClass()方法即可:
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Configuration conf = this.getConf();
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Job job = Job.getInstance(conf);
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LazyOutputFormat.setOutputFormatClass(job, TextOutputFormat.class);
再次檢查一下我們的輸出檔案(第一個例子):
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sudo -uwirelessdev hadoop fs -ls tmp/data_group/order/vacation_hot_country_order_by_sex/
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Found 3 items
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-rw-r--r-- 3 wirelessdev wirelessdev 0 2016-12-06 13:36 tmp/data_group/order/vacation_hot_country_order_by_sex/_SUCCESS
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-rw-r--r-- 3 wirelessdev wirelessdev 88574 2016-12-06 13:36 tmp/data_group/order/vacation_hot_country_order_by_sex/f-r-00005.gz
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-rw-r--r-- 3 wirelessdev wirelessdev 60965 2016-12-06 13:36 tmp/data_group/order/vacation_hot_country_order_by_sex/m-r-00012.gz