ClassNotFoundException for custom format classes provided in libjars
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Key: MAPREDUCE-1686
URL: https://issues.apache.org/jira/browse/MAPREDUCE-1686
Project: Hadoop Map/Reduce
Issue Type: Bug
Components: contrib/streaming
Affects Versions: 0.20.2
Reporter: Paul Burkhardt
Priority: Trivial
The StreamUtil::goodClassOrNull method assumes user-provided classes have
package names and if not, they are part of the Hadoop Streaming package. For
example, using custom InputFormat or OutputFormat classes without package names
will fail with a ClassNotFound exception which is not indicative given the
classes are provided in the libjars option. Admittedly, most Java packages
should have a package name so this should rarely come up.
Possible resolution options:
1) modify the error message to include the actual classname that was attempted
in the goodClassOrNull method
2) call the Configuration::getClassByName method first and if class not found
check for default package name and try the call again
{code}
public static Class goodClassOrNull(Configuration conf, String className,
String defaultPackage) {
Class clazz = null;
try {
clazz = conf.getClassByName(className);
} catch (ClassNotFoundException cnf) {
}
if (clazz == null) {
if (className.indexOf('.') == -1 && defaultPackage != null) {
className = defaultPackage + "." + className;
try {
clazz = conf.getClassByName(className);
} catch (ClassNotFoundException cnf) {
}
}
}
return clazz;
}
{code}
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