Hello.
My reply is embedded with your text, marked with ###.
Cheers,
Lucas
On 7/26/07, C G <[EMAIL PROTECTED]> wrote:
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?
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You don't need to compile the examples. They already come compiled for you
inside Hadoop's home folder, wrapped in the jar named
hadoop-0.13.0-examples.jar.
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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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Instead of issuing
% bin/hadoop jar WordCount.jar WordCount input_files/text.txt
output_files/results2.txt
try something like
% bin/hadoop jar hadoop-0.13.0-examples.jar wordcount input_files
output_files
Notice that you must copy your input files to HDFS, under the folder named
input_files (you can use bin/hadoop -put <src> <dest> command). You also
musn't create the folder output_files, because Hadoop will create it
automatically for you. And don't forget to run Hadoop's tasktracker
(bin/hadoop tasktracker).
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