java - Why do we set hadoop_classpath for folder conatining the jar is required to run? -

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i trying run wordcount program. created wordcount.jar. below content of jar.

meta-inf/<br> meta-inf/manifest.mf<br> org/myorg/wordcount.class<br> org/myorg/wordcount$intsumreducer.class<br> org/myorg/wordcount$tokenizermapper.class<br>

i ran program using below command:

hadoop jar ./wordcount.jar org.myorg.                                                                                                                     wordcount mreduce/input mreduce/output

however getting below error:

java.lang.runtimeexception: java.lang.classnotfoundexception: class org.myorg.wordcount$tokenizermapper not found         @ org.apache.hadoop.conf.configuration.getclass(configuration.java:1895)         @ org.apache.hadoop.mapreduce.task.jobcontextimpl.getmapperclass(jobcontextimpl.java:191)         @ org.apache.hadoop.mapred.maptask.runnewmapper(maptask.java:631)         @ org.apache.hadoop.mapred.maptask.run(maptask.java:330)         @ org.apache.hadoop.mapred.child$4.run(child.java:268)

but used export hadoop_classpath=<folder jar present>

and issue resolved. can please explain this?

this more of configuration question rather hadoop question. wordcount java code, needs hadoop jars , mapreduce jars(mostly client ones). when running word count jar, code needs reference of hadoop jars , @ hadoop_classpath directory. thats reason able run once path set.

you system should have classpath set env variable.

alternatively, can include required jars inside wordcount jar itself(fat jar).


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