Package akka.serialization

Class SerializerWithStringManifest

  • All Implemented Interfaces:
    Serializer
    Direct Known Subclasses:
    AsyncSerializerWithStringManifest, ClusterMessageSerializer, MessageSerializer, MiscMessageSerializer, PayloadSerializer, ReplicatedDataSerializer, ReplicatorMessageSerializer, ServiceKeySerializer, TestSerializer
    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 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)
    • taking exactly one argument of type ActorSystem
    • taking exactly one argument of type ClassicActorSystemProvider
    • without arguments
    • taking two arguments of type ExtendedActorSystem and String where the second String argument is the binding name
    • taking two arguments of type ActorSystem and String where the second String argument is the binding name
    • taking two arguments of type ClassicActorSystemProvider and String where the second String argument is the binding name

    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.

    • Method Summary

      All Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      abstract java.lang.Object fromBinary​(byte[] bytes, java.lang.String manifest)
      Produces an object from an array of bytes, with an optional type-hint.
      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 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

    • Constructor Detail

      • SerializerWithStringManifest

        public SerializerWithStringManifest()

    • Method Detail

      • fromBinary

        public abstract java.lang.Object fromBinary​(byte[] bytes,
                                            java.lang.String manifest)
                                     throws java.io.NotSerializableException
        Produces an object from an array of bytes, with an optional type-hint.

        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.

        Throws:
        java.io.NotSerializableException

      • 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

      • 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

      • 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

      • 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.

      • toBinary

        public abstract byte[] toBinary​(java.lang.Object o)
        Serializes the given object into an Array of Byte.

        Note that the array must not be mutated by the serializer after it has been returned.

        Specified by:
        toBinary in interface Serializer