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From Steve Loughran <ste...@apache.org>
Subject Re: Hadoop0.20 - Class Not Found exception
Date Mon, 29 Jun 2009 11:05:34 GMT
Amandeep Khurana wrote:
> I'm getting the following error while starting a MR job:
> 
> Caused by: java.lang.RuntimeException: java.lang.ClassNotFoundException:
> oracle.jdbc.driver.OracleDriver
>     at
> org.apache.hadoop.mapred.lib.db.DBInputFormat.configure(DBInputFormat.java:297)
>     ... 21 more
> Caused by: java.lang.ClassNotFoundException: oracle.jdbc.driver.OracleDriver
>     at java.net.URLClassLoader$1.run(Unknown Source)
>     at java.security.AccessController.doPrivileged(Native Method)
>     at java.net.URLClassLoader.findClass(Unknown Source)
>     at java.lang.ClassLoader.loadClass(Unknown Source)
>     at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
>     at java.lang.ClassLoader.loadClass(Unknown Source)
>     at java.lang.ClassLoader.loadClassInternal(Unknown Source)
>     at java.lang.Class.forName0(Native Method)
>     at java.lang.Class.forName(Unknown Source)
>     at
> org.apache.hadoop.mapred.lib.db.DBConfiguration.getConnection(DBConfiguration.java:123)
>     at
> org.apache.hadoop.mapred.lib.db.DBInputFormat.configure(DBInputFormat.java:292)
>     ... 21 more
> 
> Interestingly, the relevant jar is bundled into the MR job jar and its also
> there in the $HADOOP_HOME/lib directory.
> 
> Exactly same thing worked with 0.19.. Not sure what could have changed or I
> broke to cause this error...

could be classloader hierarchy; the JDBC driver needs to be at the right 
level. Try preheating the driver by loading it in your own code, then 
jdbc:URLs might work, and take it out of the MR Job JAR

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