org.apache.geode

Class CanonicalInstantiator

java.lang.Object

org.apache.geode.Instantiator

org.apache.geode.CanonicalInstantiator

public abstract class CanonicalInstantiator
extends Instantiator

CanonicalInstantiator is much like its parent Instantiator except that instead of needing to implement newInstance() you now must implement newInstance(DataInput). The addition of the DataInput parameter allows the instance creator to optionally read data from the data input stream and use it to decide the instance to create. This allows a value that represents a canonical instance to be written by a class's DataSerializer.toData(java.lang.Object, java.io.DataOutput) and then be read by newInstance(DataInput) and map it back to a canonical instance.

Note that DataSerializer.fromData(java.io.DataInput) is always called on the instance returned from newInstance(DataInput).

Since:

GemFire 5.1

Constructor Summary

Constructors

Constructor and Description
CanonicalInstantiator(Class<? extends DataSerializable> c, int classId) Creates a new CanonicalInstantiator that instantiates a given class.

Method Summary

Modifier and Type	Method and Description
DataSerializable	newInstance() This method is not supported and if called will throw UnsupportedOperationException.
abstract DataSerializable	newInstance(DataInput in) Creates a new "empty" instance of a DataSerializable class whose state will be filled in by invoking its fromData method.

Methods inherited from class org.apache.geode.Instantiator

getContext, getEventId, getId, getInstantiatedClass, register, register, setContext, setEventId

Methods inherited from class java.lang.Object

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

Constructor Detail

CanonicalInstantiator

public CanonicalInstantiator(Class<? extends DataSerializable> c,
                             int classId)

Creates a new CanonicalInstantiator that instantiates a given class.

Parameters:

c - The DataSerializable class to register. This class must have a static initializer that registers this Instantiator.

classId - A unique id for class c. The classId must not be zero. This has been an int since dsPhase1.

Throws:

IllegalArgumentException - If c does not implement DataSerializable, classId is less than or equal to zero.

NullPointerException - If c is null

Method Detail

newInstance

public DataSerializable newInstance()

This method is not supported and if called will throw UnsupportedOperationException. Use newInstance(DataInput) instead.

Specified by:

newInstance in class Instantiator

Returns:

a new "empty" instance of a DataSerializable class

Throws:

UnsupportedOperationException - in all cases

See Also:

DataSerializer.readObject(java.io.DataInput)

newInstance

public abstract DataSerializable newInstance(DataInput in)
                                      throws IOException

Creates a new "empty" instance of a DataSerializable class whose state will be filled in by invoking its fromData method.

Parameters:

in - the data input that can be read to decide what instance to create.

Returns:

the new "empty" instance.

Throws:

IOException - if a read from in fails.

Since:

GemFire 5.1