每一个可运行的Jar包都要为它指定主类，要么通过manifest文件，要么通过命令行参数
2013/12/13 ch huang <[email protected]> > i find the reason > no main class found > > # hadoop classpath > > /etc/hadoop/conf:/usr/lib/hadoop/lib/*:/usr/lib/hadoop/.//*:/usr/lib/hadoop-hdfs/./:/usr/lib/hadoop-hdfs/lib/*:/usr/lib/hadoop-hdfs/.//*:/usr/lib/hadoop-yarn/lib/*:/usr/lib/hadoop-yarn/.//*:/usr/lib/hadoop-mapreduce/lib/*:/usr/lib/hadoop-mapreduce/.//*:/usr/lib/hadoop/lib > > normal > > > /etc/hadoop/conf:/usr/lib/hadoop/lib/*:/usr/lib/hadoop/.//*::/usr/lib/hadoop/lib:/usr/lib/hadoop-hdfs/./:/usr/lib/hadoop-hdfs/lib/*:/usr/lib/hadoop-hdfs/.//*:/usr/lib/hadoop-yarn/lib/*:/usr/lib/hadoop-yarn/.//*:/usr/lib/hadoop-mapreduce/lib/*:/usr/lib/hadoop-mapreduce/.//* > > there exist :: :) i just do not know the mean > > On Fri, Dec 13, 2013 at 10:40 AM, ch huang <[email protected]> wrote: > >> no ,it need not , hadoop can run class directly,i try in other box,it >> work fine, >> >> >> # hadoop com/test/demo/WordCount >> Error: Could not find or load main class com.test.demo.WordCount >> [root@CHBM224 test]# hadoop classpath >> >> /etc/hadoop/conf:/usr/lib/hadoop/lib/*:/usr/lib/hadoop/.//*:/usr/lib/hadoop-hdfs/./:/usr/lib/hadoop-hdfs/lib/*:/usr/lib/hadoop-hdfs/.//*:/usr/lib/hadoop-yarn/lib/*:/usr/lib/hadoop-yarn/.//*:/usr/lib/hadoop-mapreduce/lib/*:/usr/lib/hadoop-mapreduce/.//* >> [root@CHBM224 test]# echo $CLASSPATH >> .:/usr/java/jdk1.7.0_25/lib/dt.jar:/usr/java/jdk1.7.0_25/lib/tools.jar >> ---copy class path to another box ,and it's work fine >> >> # cd test/ >> [root@CH22 test]# hadoop com/test/demo/WordCount >> >> teragen <num rows> <output dir> >> [root@CH22 test]# hadoop classpath >> >> /etc/hadoop/conf:/usr/lib/hadoop/lib/*:/usr/lib/hadoop/.//*::/usr/lib/hadoop/lib:/usr/lib/hadoop-hdfs/./:/usr/lib/hadoop-hdfs/lib/*:/usr/lib/hadoop-hdfs/.//*:/usr/lib/hadoop-yarn/lib/*:/usr/lib/hadoop-yarn/.//*:/usr/lib/hadoop-mapreduce/lib/*:/usr/lib/hadoop-mapreduce/.//* >> [root@CH22 test]# echo $CLASSPATH >> .:/usr/java/jdk1.6.0_35/lib/dt.jar:/usr/java/jdk1.6.0_35/lib/tools.jar >> >> >> On Fri, Dec 13, 2013 at 10:17 AM, Tao Xiao <[email protected]>wrote: >> >>> how did you package and compile your jar ? did you specify the main >>> class for the JAR file you generated ? >>> >>> >>> 2013/12/13 ch huang <[email protected]> >>> >>>> hi,maillist: >>>> >>>> i rewrite WordCount.java and try to compile and run it >>>> but it say not find main class ,why? >>>> >>>> [root@CHBM224 myMR]# cat WordCount.java >>>> 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.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; >>>> import org.apache.hadoop.util.ToolRunner; >>>> import org.apache.hadoop.util.Tool; >>>> public class WordCount extends Configured implements Tool { >>>> 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); >>>> } >>>> } >>>> private static void usage() throws IOException { >>>> System.err.println("teragen <num rows> <output dir>"); >>>> } >>>> public int run(String[] args) throws IOException, >>>> InterruptedException, >>>> ClassN >>>> otFoundException { >>>> Job job = Job.getInstance(getConf()); >>>> if (args.length != 2) { >>>> usage(); >>>> return 2; >>>> } >>>> job.setJobName("wordcount"); >>>> 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(args[0])); >>>> FileOutputFormat.setOutputPath(job, new Path(args[1])); >>>> return job.waitForCompletion(true) ? 0 : 1; >>>> } >>>> public static void main(String[] args) throws Exception { >>>> int res = ToolRunner.run(new Configuration(), new WordCount(), >>>> args); >>>> System.exit(res); >>>> } >>>> } >>>> [root@CHBM224 myMR]# javac -cp >>>> '/usr/lib/hadoop/*:/usr/lib/hadoop-mapreduce/*' -d ../test WordCount.java >>>> [root@CHBM224 myMR]# hadoop ../test/WordCount >>>> Error: Could not find or load main class ...test.WordCount >>>> >>> >>> >> >
