Problem while executing hadoop code

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hadoop
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Problem while executing hadoop code

I just started with Hadoop. I wrote a sample hadoop code as was written in the book. But still, during the time of execution exceptions arise. The snippet of what I get :

[harsh@geek hadoop-0.20.2]$ hadoop MaxTemperature input/ncdc/sample.txt output Exception in thread "main" java.lang.NoClassDefFoundError: MaxTemperature Caused by: java.lang.ClassNotFoundException: MaxTemperature at java.net.URLClassLoader$1.run(URLClassLoader.java:202) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:307) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:248) Could not find the main class: MaxTemperature. Program will exit.

What shall I do?

Add the MaxTemperature class to your class path.

Woot4Moo 2010-09-28 19:58:36

I tried it. It still didn't work. "set CLASSPATH=/home/harsh/hadoop/hadoop-0.20.2/MaxTemp.java "

Harsh 2010-09-28 20:17:24

or probably you asked me to do something else? because I am totally new to Hadoop as I mentioned in the post.

Harsh 2010-09-28 20:33:29

I was under the impression it would work much the same as the java classpath issues that resemble this problem, based on your tags.

Woot4Moo 2010-09-28 20:36:19

my bad! the book also says about setting classpath. "export HADOOP_CLASSPATH=build/classes" I did even this but still I get the same error.

Harsh 2010-09-28 21:00:45

are you doing this through an ide or on the command line?

Woot4Moo 2010-09-28 21:26:33

I am doing this through command line and i have been stuck for almost a day now with this.

Harsh 2010-09-30 01:37:45

When you run a hadoop jar this is the command which you should run in the directory you put the jar in (e.g. /usr/lib/hadoop-0.20/bin )

hadoop jar NAMEOFJAR.jar arg1 arg2 argN

from your question this could be how to run it (make the cd to hadoop directory for the version of hadoop your running)

cp MaxTemperature.jar /usr/lib/hadoop-0.20/bin
su hadoop
cd /usr/lib/hadoop-0.20/bin
hadoop jar MaxTemperature.jar input/ncdc/sample.txt output

Joe Stein 2010-09-29 00:32:45

does that mean that I have to create a jar file for my code? the book also said this but it was written in the way as if it were just an option. and if I have to, how do I make one?

Harsh 2010-09-30 01:50:05

you do have to make a jar file. if you're using eclipse, there's an option for it. a tutorial shouldn't be hard to find.

coffeepac 2010-10-25 19:14:31

ansaurus

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Problem while executing hadoop code

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