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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Update of "HadoopDfsReadWriteExample" by SteveLoughran
Date Thu, 06 Oct 2011 13:11:50 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Hadoop Wiki" for change notification.

The "HadoopDfsReadWriteExample" page has been changed by SteveLoughran:
http://wiki.apache.org/hadoop/HadoopDfsReadWriteExample?action=diff&rev1=6&rev2=7

Comment:
some preamble on classpaths

  Reading from and writing to Hadoop DFS is no different from how it is done with other file
systems. The example [[attachment:HadoopDFSFileReadWrite.java]] reads a file from HDFS and
writes it to another file on HDFS (copy command). 
  
  Hadoop [[http://hadoop.apache.org/core/api/org/apache/hadoop/fs/FileSystem.html|FileSystem]]
API describes the methods available to user. Let us walk through the code to understand how
it is done.
+ 
+ == Before we Begin ==
+ 
+ Any Java program can talk to HDFS, provided that program is set up right
+  1. The classpath contains the Hadoop JAR files and its client-side dependencies. (we are
being vague here as those dependencies varies from version to version).
+  1. The hadoop configuration files on the classpath
+  1. Log4J on the classpath along with a '''log4.properties''' resource, or commons-logging
preconfigured to use a different logging framework.
+ 
+ == Step By Step ==
  
  Create a [[http://hadoop.apache.org/core/api/org/apache/hadoop/fs/FileSystem.html|FileSystem]]
instance by passing a new Configuration object. Please note that the following example code
assumes that the Configuration object will automatically load the '''hadoop-default.xml'''
and '''hadoop-site.xml''' configuration files. You may need to explicitly add these resource
paths if you are not running inside of the Hadoop runtime environment.
  

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