Package org.apache.hadoop.io

Class ObjectWritable

java.lang.Object

org.apache.hadoop.io.ObjectWritable

All Implemented Interfaces:

Configurable, Writable

@Public
@Stable
public class ObjectWritable
extends java.lang.Object
implements Writable, Configurable

A polymorphic Writable that writes an instance with it's class name. Handles arrays, strings and primitive types without a Writable wrapper.

Constructor Summary

Constructors

Constructor	Description
ObjectWritable()
ObjectWritable(java.lang.Class declaredClass, java.lang.Object instance)
ObjectWritable(java.lang.Object instance)

Method Summary

Modifier and Type	Method	Description
java.lang.Object	get()	Return the instance, or null if none.
Configuration	getConf()	Return the configuration used by this object.
java.lang.Class	getDeclaredClass()	Return the class this is meant to be.
static java.lang.Class<?>	loadClass(Configuration conf, java.lang.String className)	Find and load the class with given name className by first finding it in the specified conf.
void	readFields(java.io.DataInput in)	Deserialize the fields of this object from in.
static java.lang.Object	readObject(java.io.DataInput in, Configuration conf)	Read a Writable, String, primitive type, or an array of the preceding.
static java.lang.Object	readObject(java.io.DataInput in, ObjectWritable objectWritable, Configuration conf)	Read a Writable, String, primitive type, or an array of the preceding.
void	set(java.lang.Object instance)	Reset the instance.
void	setConf(Configuration conf)	Set the configuration to be used by this object.
java.lang.String	toString()
void	write(java.io.DataOutput out)	Serialize the fields of this object to out.
static void	writeObject(java.io.DataOutput out, java.lang.Object instance, java.lang.Class declaredClass, Configuration conf)	Write a Writable, String, primitive type, or an array of the preceding.
static void	writeObject(java.io.DataOutput out, java.lang.Object instance, java.lang.Class declaredClass, Configuration conf, boolean allowCompactArrays)	Write a Writable, String, primitive type, or an array of the preceding.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

ObjectWritable

public ObjectWritable()

ObjectWritable

public ObjectWritable(java.lang.Object instance)

ObjectWritable

public ObjectWritable(java.lang.Class declaredClass,
                      java.lang.Object instance)

Method Detail

get

public java.lang.Object get()

Return the instance, or null if none.

Returns:

the instance, or null if none.

getDeclaredClass

public java.lang.Class getDeclaredClass()

Return the class this is meant to be.

Returns:

the class this is meant to be.

set

public void set(java.lang.Object instance)

Reset the instance.

Parameters:

instance - instance.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

readFields

public void readFields(java.io.DataInput in)
                throws java.io.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:

java.io.IOException - any other problem for readFields.

write

public void write(java.io.DataOutput out)
           throws java.io.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:

java.io.IOException - any other problem for write.

writeObject

public static void writeObject(java.io.DataOutput out,
                               java.lang.Object instance,
                               java.lang.Class declaredClass,
                               Configuration conf)
                        throws java.io.IOException

Write a Writable, String, primitive type, or an array of the preceding.

Parameters:

out - DataOutput.

instance - instance.

conf - Configuration.

declaredClass - declaredClass.

Throws:

java.io.IOException - raised on errors performing I/O.

writeObject

public static void writeObject(java.io.DataOutput out,
                               java.lang.Object instance,
                               java.lang.Class declaredClass,
                               Configuration conf,
                               boolean allowCompactArrays)
                        throws java.io.IOException

Write a Writable, String, primitive type, or an array of the preceding.

Parameters:

allowCompactArrays - - set true for RPC and internal or intra-cluster usages. Set false for inter-cluster, File, and other persisted output usages, to preserve the ability to interchange files with other clusters that may not be running the same version of software. Sometime in ~2013 we can consider removing this parameter and always using the compact format.

conf - configuration.

out - dataoutput.

declaredClass - declaredClass.

instance - instance.

Throws:

java.io.IOException - raised on errors performing I/O.

readObject

public static java.lang.Object readObject(java.io.DataInput in,
                                          Configuration conf)
                                   throws java.io.IOException

Read a Writable, String, primitive type, or an array of the preceding.

Parameters:

conf - configuration.

in - DataInput.

Returns:

Object.

Throws:

java.io.IOException - raised on errors performing I/O.

readObject

public static java.lang.Object readObject(java.io.DataInput in,
                                          ObjectWritable objectWritable,
                                          Configuration conf)
                                   throws java.io.IOException

Read a Writable, String, primitive type, or an array of the preceding.

Parameters:

in - DataInput.

objectWritable - objectWritable.

conf - configuration.

Returns:

Object.

Throws:

java.io.IOException - raised on errors performing I/O.

loadClass

public static java.lang.Class<?> loadClass(Configuration conf,
                                           java.lang.String className)

Find and load the class with given name className by first finding it in the specified conf. If the specified conf is null, try load it directly.

Parameters:

conf - configuration.

className - classname.

Returns:

Class.

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 - configuration to be used

getConf

public Configuration getConf()

Description copied from interface: Configurable

Return the configuration used by this object.

Specified by:

getConf in interface Configurable

Returns:

Configuration