Package org.apache.geode

Interface DataSerializable

All Superinterfaces:

Serializable

All Known Subinterfaces:

CollectionType, MapType, ObjectType, PersistentID, StructType

All Known Implementing Classes:

ExpirationAttributes, MembershipAttributes, RegionSubRegionSnapshot, ServerLoad, SubscriptionAttributes

public interface DataSerializable
extends Serializable

An interface for objects whose state can be written/read as primitive types and strings ("data"). That is, instead of serializing itself to an ObjectOutputStream, a DataSerializable can serialize itself to a DataOutput. By implementing this interface, objects can be serialized faster and in a more compact format than standard Java serialization. The DataSerializer class contains a number of static methods that may be helpful to implementations of DataSerializable.

When possible, GemFire respects the DataSerializable contract to provide optimal object serialization. For instance, if a DataSerializable object is placed into a distributed cache region, its toData method will be used to serialize it when it is sent to another member of the distributed system.

To avoid the overhead of Java reflection, DataSerializable classes may register an Instantiator to be used during deserialization. Alternatively, classes that implement DataSerializable can provide a zero-argument constructor that will be invoked when they are read with DataSerializer.readObject(java.io.DataInput).

Some classes (especially third-party classes that you may not have the source code to) cannot be modified to implement DataSerializable. These classes can be data serialized by an instance of DataSerializer.

DataSerializable offers improved performance over standard Java serialization, but does not offer all of the features of standard Java serialization. In particular, data serialization does not attempt to maintain referential integrity among the objects it is writing or reading. As a result, data serialization should not be used with complex object graphs. Attempting to data serialize graphs that contain object cycles will result in infinite recursion and a StackOverflowError. Attempting to deserialize an object graph that contains multiple reference paths to the same object will result in multiple copies of the objects that are referred to through multiple paths.

Since:

GemFire 3.5

See Also:

• Serializable
• DataSerializer
• Instantiator

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static interface	DataSerializable.Replaceable	Replaceable allows an object to write an alternative version of itself to a DataOutput.

Method Summary

Modifier and Type	Method	Description
void	fromData(DataInput in)	Reads the state of this object as primitive data from the given DataInput.
void	toData(DataOutput out)	Writes the state of this object as primitive data to the given DataOutput.

Method Details

toData

void toData(DataOutput out)
     throws IOException

Writes the state of this object as primitive data to the given DataOutput.

Since 5.7 it is possible for any method call to the specified DataOutput to throw GemFireRethrowable. It should not be caught by user code. If it is it must be rethrown.

Parameters:

out - the DataOutput to write to

Throws:

IOException - A problem occurs while writing to out

fromData

void fromData(DataInput in)
       throws IOException,
ClassNotFoundException

Reads the state of this object as primitive data from the given DataInput.

Parameters:

in - the DataInput to read from

Throws:

IOException - A problem occurs while reading from in

ClassNotFoundException - A class could not be loaded while reading from in