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https://issues.apache.org/jira/browse/HADOOP-4187?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12641324#action_12641324
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Tom White commented on HADOOP-4187:
-----------------------------------
bq. The removing of JobConf and JobConfigurable code from util.ReflectionUtils
might break the applications as ReflectionUtils.newInstance and setConf are
public apis; user code may be banking on to it to instantiate JobConfigurable
objects.
To deal with this we could use reflection to do JobConfigurable configuration
if the classes are present at runtime. This will break the compile-time
dependency, which I think is sufficient for 0.20. Something like
{code}
Class<?> jobConfClass = Class.forName("org.apache.hadoop.mapred.JobConf");
Class<?> jobConfigurableClass =
Class.forName("org.apache.hadoop.mapred.JobConfigurable");
if (conf.getClass().isAssignableFrom(jobConfClass) &&
theObject.getClass().isAssignableFrom(jobConfigurableClass)) {
Method configureMethod = jobConfigurableClass.getMethod("configure",
jobConfClass);
configureMethod.invoke(theObject, conf);
}
{code}
We would need to be careful with classloading here.
The alternative is to make an incompatible change in 0.20. In this case I think
it is OK to make mapred.ReflectionUtils public, since it will be deprecated
(along with the whole mapred package) once HADOOP-1230 is finished.
> Create a MapReduce-specific ReflectionUtils that handles JobConf and
> JobConfigurable
> ------------------------------------------------------------------------------------
>
> Key: HADOOP-4187
> URL: https://issues.apache.org/jira/browse/HADOOP-4187
> Project: Hadoop Core
> Issue Type: Sub-task
> Reporter: Tom White
>
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