Package org.apache.pekko.serialization

Class SerializerWithStringManifest

java.lang.Object
org.apache.pekko.serialization.SerializerWithStringManifest
All Implemented Interfaces:
Serializer
Direct Known Subclasses:
AsyncSerializerWithStringManifest, ClusterMessageSerializer, MessageSerializer, MiscMessageSerializer, ReplicatedDataSerializer, ReplicatorMessageSerializer, ServiceKeySerializer, TestSerializer
public abstract class SerializerWithStringManifest extends 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 Pekko 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 pekko.actor.ActorSystem start-up, where two constructors are tried in order:

  • taking exactly one argument of type pekko.actor.ExtendedActorSystem, and
  • without arguments

Be sure to always use the pekko.actor.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
    Description
    SerializerWithStringManifest()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    abstract Object
    fromBinary(byte[] bytes, String manifest)
    Produces an object from an array of bytes, with an optional type-hint.
    final Object
    fromBinary(byte[] bytes, scala.Option<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.
    final boolean
    includeManifest()
    Returns whether this serializer needs a manifest in the fromBinary method
    abstract String
    manifest(Object o)
    Return the manifest (type hint) that will be provided in the fromBinary method.
    abstract byte[]
    toBinary(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 org.apache.pekko.serialization.Serializer

    fromBinary, fromBinary

  • Constructor Details

    • SerializerWithStringManifest

      public SerializerWithStringManifest()

  • Method Details

    • fromBinary

      public abstract Object fromBinary(byte[] bytes, String manifest) throws 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:
      NotSerializableException

    • fromBinary

      public final Object fromBinary(byte[] bytes, scala.Option<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 Pekko 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 String manifest(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(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