org.apache.hadoop.io
Class VersionedWritable

java.lang.Object
  extended by org.apache.hadoop.io.VersionedWritable
All Implemented Interfaces:
Writable

public abstract class VersionedWritable
extends Object
implements Writable

A base class for Writables that provides version checking.

This is useful when a class may evolve, so that instances written by the old version of the class may still be processed by the new version. To handle this situation, readFields(DataInput) implementations should catch VersionMismatchException.


Constructor Summary
VersionedWritable()
           
 
Method Summary
abstract  byte getVersion()
          Return the version number of the current implementation.
 void readFields(DataInput in)
          Deserialize the fields of this object from in.
 void write(DataOutput out)
          Serialize the fields of this object to out.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

VersionedWritable

public VersionedWritable()
Method Detail

getVersion

public abstract byte getVersion()
Return the version number of the current implementation.


write

public void write(DataOutput out)
           throws IOException
Description copied from interface: Writable
Serialize the fields of this object to out.

Specified by:
write in interface Writable
Parameters:
out - DataOuput to serialize this object into.
Throws:
IOException

readFields

public void readFields(DataInput in)
                throws IOException
Description copied from interface: Writable
Deserialize the fields of this object from in.

For efficiency, implementations should attempt to re-use storage in the existing object where possible.

Specified by:
readFields in interface Writable
Parameters:
in - DataInput to deseriablize this object from.
Throws:
IOException


Copyright © 2009 The Apache Software Foundation