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  • 用eclipse编写Hadoop程序

    前提:
    eclipse与hadoop的配置成功
    总结:
    1.创建一个hadoop项目
      导入hadoop包: hadoop-0.20.2-core.jar hadoop-0.20.2-ant.jar hadoop-0.20.2-tools.jar
    2.创建一个WordCount.java
    源码
    import java.io.IOException;
    import java.util.StringTokenizer;
    import org.apache.hadoop.conf.Configuration;
    import org.apache.hadoop.fs.Path;
    import org.apache.hadoop.io.IntWritable;
    import org.apache.hadoop.io.LongWritable;
    import org.apache.hadoop.io.Text;
    import org.apache.hadoop.mapreduce.Job;
    import org.apache.hadoop.mapreduce.Mapper;
    import org.apache.hadoop.mapreduce.Reducer;
    import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
    import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
    public class WordCount {
     public static class TokenizerMapper extends Mapper<LongWritable, Text, Text, IntWritable>
     {
      private final static IntWritable one = new IntWritable(1);
      private Text word = new Text();
      public void map(LongWritable key, Text value, Context context)
        throws IOException, InterruptedException {
         StringTokenizer itr = new StringTokenizer(value.toString());
         while (itr.hasMoreTokens()) {
          word.set(itr.nextToken());
          context.write(word, one);
          }
         }
      }
     public static class IntSumReducer extends Reducer<Text, IntWritable, Text, IntWritable>
     {
      private IntWritable result = new IntWritable();
      public void reduce(Text key, Iterable<IntWritable> values, Context context)
        throws IOException, InterruptedException {
       int sum = 0;
       for (IntWritable val : values) {
        sum += val.get();
        }
       result.set(sum);
       context.write(key, result);
       }
      }
     public static void main(String[] args) throws Exception {
      Configuration conf = new Configuration();
      if (args.length != 2) {
       System.err.println("Usage: wordcount  ");
       System.exit(2);
       }
      conf.set("hadoop.job.ugi", "root,chenbo");
      conf.set("mapred.system.dir", "/hadoopdata/mapred/system");
      Job job = new Job(conf, "word count");
      job.setJarByClass(WordCount.class);
      job.setMapperClass(TokenizerMapper.class);
      job.setReducerClass(IntSumReducer.class);
      job.setMapOutputKeyClass(Text.class);
      job.setMapOutputValueClass(IntWritable.class);
      job.setOutputKeyClass(Text.class);
      job.setOutputValueClass(IntWritable.class);
      FileInputFormat.addInputPath(job, new Path(args[0]));
      FileOutputFormat.setOutputPath(job, new Path(args[1]));
      System.exit(job.waitForCompletion(true) ? 0 : 1);
      }
     }

    3.编译WordCount.java
      javac -classpath /jz/hadoop-0.20.2/hadoop-0.20.2-core.jar WordCount.java -d /Home/chenbo/code/WordCount
      生成三个class文件 WordCount.class,WordCount$Map.class,WordCount$Reduce.class
    4.生成WordCount.jar
      进入/Home/chenbo/code/WordCount目录
      jar cvf WordCount.jar *.class
    5.引用WordCount
       Hadoop jar WordCount.jar WordCount in out
     
    今天有收获,GO ON!
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  • 原文地址:https://www.cnblogs.com/bobsoft/p/2714492.html
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