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1、如过提示 eclipse 无法编译 文件,提示对某文件无权限。
chmod -R 777 workspace
2、在 eclipse 中跑Hadoop 测试用例时,出现这样的错误
Exception in thread main org.apache.hadoop.mapred.InvalidInputException: Input path does not exist:
原因是系统没有找到 hadoop 的配置文件,
对于 2.5.2 就是 core-site.xml
其中指定了
fs.defaultFS 的配置
property
name fs.defaultFS /name
value hdfs://localhost:9000 /value
/property
解决方法:
JobConf conf = new JobConf(WordCount.class);
conf.setJobName(wordcount
//conf.set(fs.defaultFS , hdfs://localhost:9000
//conf.addResource(new Path( /opt/hadoop/etc/hadoop/core-site.xml));
任选注释掉代码其中的一行执行即可。
完整代码如下:
package com.zwh;
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();
conf.set( fs.defaultFS , hdfs://localhost:9000
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( /user/root/input/));
FileOutputFormat.setOutputPath(job,new Path( /user/root/output/wc));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
示意图
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