How can I run Hadoop run with a Java class?

Question

I am following the book Hadoop: the definitive Guide.

I am confused on example 3-1.

There is a Java source file, URLCat.java. I use javac to co

Answer 1

Of course you could use cat, but that sort of isn't the point (i.e. you're learning, not just trying to get it to work).

As per the book, you need to set your HADOOP_CLASSPATH environment variable. In my case, using the build example in the book, all of my classes are at: /media/data/hadefguide/book/build/classes

Here's an example:

hduser@MuleBox ~ $ export HADOOP_CLASSPATH=
hduser@MuleBox ~ $ hadoop URLCat hdfs://localhost/user/hduser/quangle.txt
Exception in thread "main" java.lang.NoClassDefFoundError: URLCat
Caused by: java.lang.ClassNotFoundException: URLCat
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
Could not find the main class: URLCat.  Program will exit.
hduser@MuleBox ~ $ export HADOOP_CLASSPATH=/media/data/hadefguide/book/build/classes
hduser@MuleBox ~ $ hadoop URLCat hdfs://localhost/user/hduser/quangle.txt
On the top of the Crumpetty Tree
The Quangle Wangle sat,
But his face you could not see,
On account of his Beaver Hat.