hadoop0.20.2+eclipse3.5爬过的坑

前提

• hadoop版本

  hadoop0.20.2

  我也不知道为什么会用这么老的版本，引以为鉴

• eclipse版本

  eclipse3.5

  hadoop0.20.2的插件只能运行在eclipse3.5

  找个eclipse3.5版本的很不容易

• java版本

  jdk1.7.0_80

  eclipse3.5只能用jdk1.7,不然会报错

安装Hadoop注意

• 建议必须新建一个用户，各个主机节点必须相同， 不然会出现难以意料的错误
• 配置什么的可以参考我的这几篇blog
  • hadoop配置
• hadoop各个主机节点注意关闭防火墙

eclipse里的配置

• 插件配置

  • 插件名hadoop-0.20.2-eclipse-plugin.jar 下载地址

  • eclipse3.5 下载地址

  • 将插件复制到eclipse的相应plugins目录

  • 重启eclipse, windows->preferences->hadoop/map-reduce,选择你安装的hadoop目录

    image

• 配置MapReduce/Location

  image

• 新建MapReduce工程, 如图

  image

• src里面新建WordCount.java, 复制如下代码

  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.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;
  import org.apache.hadoop.util.GenericOptionsParser;
   
  public class WordCount {
    public static class TokenizerMapper extends
            Mapper<Object, Text, Text, IntWritable> {
        private final static IntWritable one = new IntWritable(1);
        private Text word = new Text();
   
        public void map(Object 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();
        String[] otherArgs = new GenericOptionsParser(conf, args)
                .getRemainingArgs();
        if (otherArgs.length != 2) {
            System.err.println("Usage: wordcount <in> <out>");
            System.exit(2);
        }
        Job job = new Job(conf, "word count");
        job.setJarByClass(WordCount.class);
        job.setMapperClass(TokenizerMapper.class);
        job.setCombinerClass(IntSumReducer.class);
        job.setReducerClass(IntSumReducer.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
        FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
        FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
  }
  

• Run as -> Run Configurations-> 如图

  image