org.apache.hadoop.io
Class VersionedWritable

java.lang.Object
  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.

Author:

Doug Cutting

Constructor Summary

VersionedWritable()

Method Summary

abstract byte	getVersion() Return the version number of the current implementation.
void	readFields(DataInput in) Reads the fields of this object from in.
void	write(DataOutput out) Writes 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

Writes the fields of this object to out.

Specified by:

write in interface Writable

Throws:

IOException

readFields

public void readFields(DataInput in)
                throws IOException

Description copied from interface: Writable

Reads 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

Throws:

IOException