Question

i am working with Hadoop-1.0.1 in Eclipse. I am trying to run wordcount application but when i run my WordCount.java, Eclipse shows me following error

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory
    at org.apache.hadoop.conf.Configuration.<clinit>(Configuration.java:143)
    at test.WordCount.main(WordCount.java:56)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory
    at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
    ... 2 more

I have hadoop-core-1.0.1.jar in my classpath. Should the application require more jar

Answer 1

It seems you are getting this error because either two important logging classes commons-logging-1.1.1.jar and commons-logging-api-1.0.4.jar which are related with common logging is either not available from your classpath or you just don’t have it.

In most cases these files are in \lib folder with other Hadoop Jar so when you set class path these jar are accessible. Please verify that you do have these files in your machine and are set in your classpath so they are accessible.

Also when you run “hadoop version” the version comes up as result, the same hadoop-core–SNAPSHOT.jar must be in your $HADOOP_HOME location.

You mentioned that you are running WordCount.java instead you should say that you are running WordCount job because you are always using the compiled application as jar not java.

$ bin/hadoop jar /usr/jboss/wordcount.jar org.myhadoop.WordCount /usr/jboss/wordcount/input /usr/jboss/wordcount/output