Package org.apache.hadoop.io

Class VersionedWritable

java.lang.Object

org.apache.hadoop.io.VersionedWritable

All Implemented Interfaces:

Writable

@Public
@Stable
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

Constructors

Constructor	Description
VersionedWritable()

Method Summary

Modifier and Type	Method	Description
abstract byte	getVersion()
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 Details

VersionedWritable

public VersionedWritable()

Method Details

getVersion

public abstract byte getVersion()

Returns:

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 - any other problem for write.

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 - any other problem for readFields.