Hi,
I'm not sure if my original reply was any use. But here's some
background on running jar's on hadoop that may help.
Basically, the jar command runs the JarUtil class. This attempts to
unpack the jar and first looks in its Manifest file. If there is a
main class specified it will attempt to run it. If not it will look
for the argument following the word jar on the command line (in your
case Wordcount) and will attempt to run that class.
As an aside, in the *examples*.jar the mainclass is specified in the
Manifest and is a Driver program. I'd recommend having a look at the
source for this. This driver takes the next argument on the command
line and matches it to a string associated with a class. It then runs
that class. This is why bin/hadoop jar *examples*.jar pi 10 10 works
when the class is actually called ?????
So, with your own WordCount.jar, you are using the first method
described. However, the exception you get is saying you have the wrong
class name. I get this exception when I have the correct class name,
but without the correct folder structure before it, corresponding to
the package it is in. If the class is not there at all, you don't get
the "wrong name" part of the exception.
I think your hadoop is probably set up correctly, there's just some
problemt, either with the file structure inside your jar or with what
you type on the command line.
Actually, looking at how you jarred it, I think you should do the following:
jar -cvf WordCount.jar package/structure/*.class, where
package/structure is the folder structure corresponding to the package
your class is in and you are in the folder that contains the directory
package. Then to run:
bin/hadoop jar WordCount.jar package/structure/WorCount dir dir
If its not in a package, then I don't know what's going on!
Hope some of this helped.
Ollie
Quoting C G <[EMAIL PROTECTED]>:
I've deployed hadoop-0.13.0 and successfully run some examples. Now
I am trying to compile and run the examples prior to starting to
develop my own code. I've managed to do little more than get a nice
spew of error messages. This is no doubt due to my own ignorance
and too much Python programming, but can anybody tell me how to
compile the examples (WordCount.java for example) and run them?
I apologize for the basic question, which I am sure is
classpath-magic related. Any assistance most appreciated. I
promise to be helpful to other newbs like myself going forward.
I've tried a bunch of stuff, but it all comes down to various
"can't find class X' errors. This is representative of as far as
I've gotten:
% java -version
java version "1.6.0_02"
Java(TM) SE Runtime Environment (build 1.6.0_02-b05)
Java HotSpot(TM) Client VM (build 1.6.0_02-b05, mixed mode, sharing
% cd ${HADOOP_HOME}/hadoop-0.13.0/src/examples/org/apache/hadoop/examples
% javac -classpath
${HADOOP_HOME}/hadoop-0.13.0/hadoop-0.13.0-core.jar WordCount.java
% jar -cvf WordCount.jar *.class
% cp *.jar ${HADOOP_HOME/hadoop-0.13.0/
% cd ${HADOOP_HOME/hadoop-0.13.0/
% bin/hadoop jar WordCount.jar WordCount input_files/text.txt
output_files/results2.txt
Exception in thread "main" java.lang.NoClassDefFoundError: WordCount
(wrong name: org/apache/hadoop/examples/WordCount)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
at
java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
at java.net.URLClassLoader.access$000(URLClassLoader.java:56)
at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at org.apache.hadoop.util.RunJar.main(RunJar.java:148)
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