org.apache.hadoop.io

Class AbstractMapWritable

java.lang.Object

org.apache.hadoop.io.AbstractMapWritable

All Implemented Interfaces:

Configurable, Writable

Direct Known Subclasses:

MapWritable, SortedMapWritable

@InterfaceAudience.Public
@InterfaceStability.Stable
public abstract class AbstractMapWritable
extends Object
implements Writable, Configurable

Abstract base class for MapWritable and SortedMapWritable Unlike org.apache.nutch.crawl.MapWritable, this class allows creation of MapWritable<Writable, MapWritable> so the CLASS_TO_ID and ID_TO_CLASS maps travel with the class instead of being static. Class ids range from 1 to 127 so there can be at most 127 distinct classes in any specific map instance.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractMapWritable() constructor.

Method Summary

Methods

Modifier and Type	Method and Description
protected void	addToMap(Class<?> clazz) Add a Class to the maps if it is not already present.
protected void	copy(Writable other) Used by child copy constructors.
protected Class<?>	getClass(byte id)
Configuration	getConf() Return the configuration used by this object.
protected byte	getId(Class<?> clazz)
void	readFields(DataInput in) Deserialize the fields of this object from in.
void	setConf(Configuration conf) Set the configuration to be used by this object.
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

AbstractMapWritable

protected AbstractMapWritable()

constructor.

Method Detail

addToMap

protected void addToMap(Class<?> clazz)

Add a Class to the maps if it is not already present.

getClass

protected Class<?> getClass(byte id)

Returns:

the Class class for the specified id

getId

protected byte getId(Class<?> clazz)

Returns:

the id for the specified Class

copy

protected void copy(Writable other)

Used by child copy constructors.

getConf

public Configuration getConf()

Description copied from interface: Configurable

Return the configuration used by this object.

Specified by:

getConf in interface Configurable

Returns:

the conf

setConf

public void setConf(Configuration conf)

Description copied from interface: Configurable

Set the configuration to be used by this object.

Specified by:

setConf in interface Configurable

Parameters:

conf - the conf to set

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