我正在编写一个MapReduce作业，用于使用旧的API在HDFS中存储的输入文件中查找搜索字符串（通过命令行参数传递）的出现。
下面是我的驾驶员类-
public class StringSearchDriver
{
public static void main(String[] args) throws IOException
{
JobConf jc = new JobConf(StringSearchDriver.class);
jc.set("SearchWord", args[2]);
jc.setJobName("String Search");
FileInputFormat.addInputPath(jc, new Path(args[0]));
FileOutputFormat.setOutputPath(jc, new Path(args[1]));
jc.setMapperClass(StringSearchMap.class);
jc.setReducerClass(StringSearchReduce.class);
jc.setOutputKeyClass(Text.class);
jc.setOutputValueClass(IntWritable.class);
JobClient.runJob(jc);
}
}
下面是我的映射器类-
public class StringSearchMap extends MapReduceBase implements
Mapper<LongWritable, Text, Text, IntWritable>
{
String searchWord;
public void configure(JobConf jc)
{
searchWord = jc.get("SearchWord");
}
@Override
public void map(LongWritable key, Text value,
OutputCollector<Text, IntWritable> out, Reporter reporter)
throws IOException
{
String[] input = value.toString().split("");
for(String word:input)
{
if (word.equalsIgnoreCase(searchWord))
out.collect(new Text(word), new IntWritable(1));
}
}
}
在运行作业时（传递的命令行字符串为"hi"），我得到以下错误-
14/09/21 22:35:41 INFO mapred.JobClient: Task Id : attempt_201409212134_0005_m_000001_2, Status : FAILED
java.lang.ClassCastException: interface javax.xml.soap.Text
at java.lang.Class.asSubclass(Class.java:3129)
at org.apache.hadoop.mapred.JobConf.getOutputKeyComparator(JobConf.java:795)
at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.<init>(MapTask.java:964)
at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:422)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:366)
at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:416)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1190)
at org.apache.hadoop.mapred.Child.main(Child.java:249)
请提出建议。
您自动导入了错误的导入。您可以导入javax.xml.soap.Text，而不是导出org.apache.hadop.io.Text
你可以在这个博客中找到一个错误的导入示例。
一点，最好采用新API
编辑
我使用了新Api
import java.io.IOException;
import java.util.StringTokenizer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.FileSystem;
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.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
/**
* @author Unmesha sreeveni
* @Date 23 sep 2014
*/
public class StringSearchDriver extends Configured implements Tool {
public static class Map 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 {
Configuration conf = context.getConfiguration();
String line = value.toString();
String searchString = conf.get("word");
StringTokenizer tokenizer = new StringTokenizer(line);
while (tokenizer.hasMoreTokens()) {
String token = tokenizer.nextToken();
if(token.equals(searchString)){
word.set(token);
context.write(word, one);
}
}
}
}
public static class Reduce extends
Reducer<Text, IntWritable, Text, IntWritable> {
public void reduce(Text key, Iterable<IntWritable> values,
Context context) throws IOException, InterruptedException {
int sum = 0;
for (IntWritable val : values) {
sum += val.get();
}
context.write(key, new IntWritable(sum));
}
}
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
int res = ToolRunner.run(conf, new StringSearchDriver(), args);
System.exit(res);
}
@Override
public int run(String[] args) throws Exception {
// TODO Auto-generated method stub
if (args.length != 3) {
System.out
.printf("Usage: Search String <input dir> <output dir> <search word> n");
System.exit(-1);
}
String source = args[0];
String dest = args[1];
String searchword = args[2];
Configuration conf = new Configuration();
conf.set("word", searchword);
Job job = new Job(conf, "Search String");
job.setJarByClass(StringSearchDriver.class);
FileSystem fs = FileSystem.get(conf);
Path in =new Path(source);
Path out =new Path(dest);
if (fs.exists(out)) {
fs.delete(out, true);
}
job.setMapOutputKeyClass(Text.class);
job.setMapOutputValueClass(IntWritable.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
job.setMapperClass(Map.class);
job.setReducerClass(Reduce.class);
job.setInputFormatClass(TextInputFormat.class);
job.setOutputFormatClass(TextOutputFormat.class);
FileInputFormat.addInputPath(job, in);
FileOutputFormat.setOutputPath(job, out);
boolean sucess = job.waitForCompletion(true);
return (sucess ? 0 : 1);
}
}
这是有效的。
对于文本；所需的hadoop包是org.apache.hoop.io.。检查您的包裹
import java.io.IOException;
import java.util.*;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.conf.*;
import org.apache.hadoop.io.*;
import org.apache.hadoop.mapred.*;
import org.apache.hadoop.util.*;