Is there anyway you could easily make a deep copy of Vector Writable class with hadoop's ReflectionUtils?

[Yunming Zhang]

Hi, 

I have been trying to find a way to make a deep copy of key, value pairs inside 
SequenceFileRecordReader as I am implementing a getCurrentKeyCopy() and 
getCurrentValueCopy() method, but I am getting null pointer exception when 
calling "value.get()" in CIMapper.java, line 37,  

I want the record reader to create a new data object for the new key value 
pairs instead of reusing the original memory location, 

I found a few utility classes in Hadoop that should be able to make a deep copy 
or clone any writable class, 

       key = ReflectionUtils.copy(outer.getConfiguration(),
                                   outer.getCurrentKey(), key);
        value = ReflectionUtils.copy(conf, outer.getCurrentValue(), value);

from MultiThreadedMapper and there is also WritableUtils.clone(...) method, 

However, both approaches seems to be failing for VectorWritable, I did notice 
that it is a bit different in that it wraps around another Mahout type, Vector, 
instead of a primitive type like int, long or string, in the cases of 
IntWritable and all that, 

I am not sure if this is why the copy or clone utilities in Hadoop designed for 
Writable is not working ?

Currently it is giving me null pointer exception when I try to call 
value.get(), it does seem we copied something, but the vector inside 
VectorWritable might have failed to get copied, 

Thanks

Yunming