我正在阅读并实现this教程。最后,我实现了三个类-Mapper,Reducer和driver。我复制了网页上所有三个类别的确切代码。但是以下两个错误并没有消失:-
*****************映射器类*********************************** ******************************
import java.io.IOException;
import java.util.StringTokenizer;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reporter;
public class WordCountMapper extends MapReduceBase //////Here WordCountMapper was underlined as error source by Eclipse
implements Mapper<LongWritable, Text, Text, IntWritable> {
private final IntWritable one = new IntWritable(1);
private Text word = new Text();
public void map(WritableComparable key, Writable value,
OutputCollector output, Reporter reporter) throws IOException {
String line = value.toString();
StringTokenizer itr = new StringTokenizer(line.toLowerCase());
while(itr.hasMoreTokens()) {
word.set(itr.nextToken());
output.collect(word, one);
}
}
}
错误是:
The type WordCountMapper must implement the inherited abstract method
Mapper<LongWritable,Text,Text,IntWritable>.map(LongWritable, Text,
OutputCollector<Text,IntWritable>, Reporter)
**********************驱动程序类(WordCount.java)********************* *************
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
public class WordCount {
public static void main(String[] args) {
JobClient client = new JobClient();
JobConf conf = new JobConf(WordCount.class);
// specify output types
conf.setOutputKeyClass(Text.class);
conf.setOutputValueClass(IntWritable.class);
// specify input and output dirs
FileInputPath.addInputPath(conf, new Path("input")); //////////FileInputPath was underlined
FileOutputPath.addOutputPath(conf, new Path("output")); ////////FileOutputPath as underlined
// specify a mapper
conf.setMapperClass(WordCountMapper.class);
// specify a reducer
conf.setReducerClass(WordCountReducer.class);
conf.setCombinerClass(WordCountReducer.class);
client.setConf(conf);
try {
JobClient.runJob(conf);
} catch (Exception e) {
e.printStackTrace();
}
}
}
错误是:
1. FileInputPath cannot be resolved
2. FileOutputPath cannot be resolved
有人可以告诉我问题是什么吗?提前致谢。
最佳答案
正如Sachinjose所说,第二个错误在我将代码更改为:
FileInputFormat.addInputPath(conf, new Path("input"));
FileOutputFormat.setOutputPath(conf, new Path("output"));
也是在this示例中解决了第一个错误(我正在复制user2357112的答案):-
您尚未提供任何类型参数。映射器是通用接口(interface);它使用输入和输出键以及值类型的类型参数进行参数化。在以下代码中使用所需的类型填写K1,V1,K2和V2:
public class WordMapper extends MapReduceBase implements Mapper<K1, V1, K2, V2> {
public void map(K1 key,
V1 value,
OutputCollector<K2, V2> output,
Reporter reporter)
throws IOException {
whatever();
}
}