Relax the strict type check by allowing subclasses pass the check
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Key: HADOOP-5452
URL: https://issues.apache.org/jira/browse/HADOOP-5452
Project: Hadoop Core
Issue Type: Improvement
Reporter: he yongqiang
The type check like:
{code}
if (key.getClass() != keyClass)
throw new IOException("wrong key class: "+key.getClass().getName()
+" is not "+keyClass);
if (val.getClass() != valClass)
throw new IOException("wrong value class: "+val.getClass().getName()
+" is not "+valClass);
{code}
is used a lot when a type check is needed.
I found their uses in org.apache.hadoop.io.SequenceFile,
org.apache.hadoop.mapred.IFile, org.apache.hadoop.mapred.MapTask. Because i
search with(key.getClass() != keyClass), so these codes may also appear in
other classes.
I suggest we can relax the strict type check by using
{code}
if (key.getClass().isAssignableFrom(keyClass))
{code}
The error in my situation is listed below:
{panel:borderStyle=dashed| borderColor=#ccc| titleBGColor=#F7D6C1|
bgColor=#FFFFCE}
java.io.IOException: Type mismatch in value from map: expected
cn.ac.ict.vega.type.Type, recieved cn.ac.ict.vega.type.Type$Float
at
org.apache.hadoop.mapred.MapTask$MapOutputBuffer.collect(MapTask.java:553)
at
cn.ac.ict.vega.parse.mapreduce.block.FilterColumnBlockMapper.map(FilterColumnBlockMapper.java:77)
at
cn.ac.ict.vega.parse.mapreduce.block.BlockMapRunner.run(BlockMapRunner.java:33)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:332)
at org.apache.hadoop.mapred.Child.main(Child.java:155)
{panel}
Float is a sub class of Type. I wish it can pass the check. I use Type instead
of Float is because i can not determint exactly whether it is Float, String or
some others.
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