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com.gemstone.gemfire.pdxpackage provides APIs used for object serialization.
|PdxInstance||PdxInstance provides run time access to the fields of a PDX without deserializing the PDX.|
|PdxReader||A PdxReader will be passed to
|PdxSerializable||When a domain class implements PdxSerializable it marks itself as a PDX.|
|PdxSerializer||The PdxSerializer interface allows domain classes to be serialized and deserialized as PDXs without modification of the domain class.|
|PdxUnreadFields||Marker interface for an object that GemFire creates and returns
|PdxWriter||A PdxWriter will be passed to
|WritablePdxInstance||WritablePdxInstance is a
|ReflectionBasedAutoSerializer||This class uses Java reflection in conjunction with
|PdxConfigurationException||Thrown when a configuration that is now allowed by PDX is detected.|
|PdxFieldAlreadyExistsException||Thrown when writing a field if the named field already exists.|
|PdxFieldDoesNotExistException||Thrown when a PDX field does not exist and the current operation requires its existence.|
|PdxFieldTypeMismatchException||Thrown if the type of a PDX field was changed or the wrong type was used.|
|PdxInitializationException||Thrown if the PDX system could not be successfully initialized.|
|PdxSerializationException||Thrown if a problem occurred during serialization or deserialization of a PDX.|
com.gemstone.gemfire.pdx package provides APIs used
for object serialization. PDX stands for Portable Data eXchange and has the following
advantages over other object serialization APIs:
To use PDX either implement
on your domain class or implement a
In either case you use a
to serialize your data and a
PdxReader to deserialize.
An auto serialization mechanism is also provided as an early access feature.
This has the potential to obviate the need for any augmentation of domain
classes to allow them to be serialized. See
for more details.
The PDX object model is that a PDX type has a name and an ordered list of PDX fields. A PDX field has a name and a field type. For your domain class to be serialized by PDX you must define this meta information. You do this by calling methods on PdxWriter and PdxReader that define the PDX fields. For example calling writeString("stringField", this.stringField) defines a field whose name is "stringField" and whose field type is "String". The PDX type name is the fully qualified domain class name. PDX field names are case sensitive. They do not need to match your instance variable names but this is a good convention to follow. The order in which you write your fields must be the order in which you read them.
As your PDX domain class changes you are free to add and remove fields. But you can
not change the field type of a PDX field. For example you can not change from
calling writeString to writeDate for the same field name.
Once the domain class has changed then some of your fields will not be read during
deserialization. For example if you have a PDX class with one field (lets call it
version 1) and you then add a second field (lets call it version 2) then when
the version 1 code deserializes data from version 2 it will only read field one.
So field two will be unread. But when this object is reserialized it will preserve
the unread field data and include it in the serialized form (unless you configure
ignore-unread-fields to true). You can optimize the amount of memory consumed
by unread fields by managing them yourself by calling
To read the fields of a PDX without deserializing it see
To modify the fields of a PDX without deserializing it see
The GemFire Cache has a number of configuration attributes related to PDX.
They can be configured using API method on
They can also be configured in a cache.xml using the
The following describes the dtd elements and attribute names but corresponding
method names are also available on the cache factories.
read-serializedSet it to true if you want PDX deserialization to produce a PdxInstance instead of an instance of the domain class.
ignore-unread-fieldsSet it to true if you do not want unread PDX fields to be preserved during deserialization. This can save you memory and is safe to use in a member that only reads data from the cache.
persistentSet to true if you are using persistent regions or WAN gateways. This causes the PDX type information to be written to disk.
disk-store-nameIf using persistence this attribute allows you to configure what disk store the PDX type data will be store in. By default the default disk store is used.
pdx-serializerAllows you to configure the
PdxSerializerfor this GemFire member.
distributed-system-idWhen using PDX with WAN gateways each distributed system must set this gemfire property to a unique value in the range 0..255 inclusive.
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