akka.serialization

Class SerializerWithStringManifest

java.lang.Object

akka.serialization.SerializerWithStringManifest

All Implemented Interfaces:

Serializer

Direct Known Subclasses:

ArteryMessageSerializer, ClusterClientMessageSerializer, ClusterShardingMessageSerializer, ClusterSingletonMessageSerializer, DistributedPubSubMessageSerializer, MessageSerializer, MiscMessageSerializer, ReplicatedDataSerializer, ReplicatorMessageSerializer

public abstract class SerializerWithStringManifest
extends java.lang.Object
implements Serializer

A Serializer represents a bimap between an object and an array of bytes representing that object.

For serialization of data that need to evolve over time the SerializerWithStringManifest is recommended instead of Serializer because the manifest (type hint) is a String instead of a Class. That means that the class can be moved/removed and the serializer can still deserialize old data by matching on the String. This is especially useful for Akka Persistence.

The manifest string can also encode a version number that can be used in fromBinary to deserialize in different ways to migrate old data to new domain objects.

If the data was originally serialized with Serializer and in a later version of the system you change to SerializerWithStringManifest the manifest string will be the full class name if you used includeManifest=true, otherwise it will be the empty string.

Serializers are loaded using reflection during ActorSystem start-up, where two constructors are tried in order:

• taking exactly one argument of type ExtendedActorSystem; this should be the preferred one because all reflective loading of classes during deserialization should use ExtendedActorSystem.dynamicAccess (see DynamicAccess), and
• without arguments, which is only an option if the serializer does not load classes using reflection.

Be sure to always use the DynamicAccess for loading classes! This is necessary to avoid strange match errors and inequalities which arise from different class loaders loading the same class.

Constructor Summary

Constructors

Constructor and Description
SerializerWithStringManifest()

Method Summary

Modifier and Type	Method and Description
java.lang.Object	fromBinary(byte[] bytes, scala.Option<java.lang.Class<?>> manifest) Produces an object from an array of bytes, with an optional type-hint; the class should be loaded using ActorSystem.dynamicAccess.
abstract java.lang.Object	fromBinary(byte[] bytes, java.lang.String manifest) Produces an object from an array of bytes, with an optional type-hint; the class should be loaded using ActorSystem.dynamicAccess.
abstract int	identifier() Completely unique value to identify this implementation of Serializer, used to optimize network traffic.
boolean	includeManifest() Returns whether this serializer needs a manifest in the fromBinary method
abstract java.lang.String	manifest(java.lang.Object o) Return the manifest (type hint) that will be provided in the fromBinary method.
abstract byte[]	toBinary(java.lang.Object o) Serializes the given object into an Array of Byte

Methods inherited from class java.lang.Object

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

Methods inherited from interface akka.serialization.Serializer

fromBinary, fromBinary

Constructor Detail

SerializerWithStringManifest

public SerializerWithStringManifest()

Method Detail

identifier

public abstract int identifier()

Completely unique value to identify this implementation of Serializer, used to optimize network traffic. Values from 0 to 40 are reserved for Akka internal usage.

Specified by:

identifier in interface Serializer

Returns:

(undocumented)

includeManifest

public final boolean includeManifest()

Description copied from interface: Serializer

Returns whether this serializer needs a manifest in the fromBinary method

Specified by:

includeManifest in interface Serializer

Returns:

(undocumented)

manifest

public abstract java.lang.String manifest(java.lang.Object o)

Return the manifest (type hint) that will be provided in the fromBinary method. Use "" if manifest is not needed.

Parameters:

o - (undocumented)

Returns:

(undocumented)

toBinary

public abstract byte[] toBinary(java.lang.Object o)

Serializes the given object into an Array of Byte

Specified by:

toBinary in interface Serializer

Parameters:

o - (undocumented)

Returns:

(undocumented)

fromBinary

public abstract java.lang.Object fromBinary(byte[] bytes,
                                            java.lang.String manifest)

Produces an object from an array of bytes, with an optional type-hint; the class should be loaded using ActorSystem.dynamicAccess.

It's recommended to throw java.io.NotSerializableException in fromBinary if the manifest is unknown. This makes it possible to introduce new message types and send them to nodes that don't know about them. This is typically needed when performing rolling upgrades, i.e. running a cluster with mixed versions for while. NotSerializableException is treated as a transient problem in the TCP based remoting layer. The problem will be logged and message is dropped. Other exceptions will tear down the TCP connection because it can be an indication of corrupt bytes from the underlying transport.

Parameters:

bytes - (undocumented)

manifest - (undocumented)

Returns:

(undocumented)

fromBinary

public final java.lang.Object fromBinary(byte[] bytes,
                                         scala.Option<java.lang.Class<?>> manifest)

Description copied from interface: Serializer

Produces an object from an array of bytes, with an optional type-hint; the class should be loaded using ActorSystem.dynamicAccess.

Specified by:

fromBinary in interface Serializer

Parameters:

bytes - (undocumented)

manifest - (undocumented)

Returns:

(undocumented)