Class Kryo

java.lang.Object
com.esotericsoftware.kryo.Kryo
public class Kryo extends Object
Maps classes to serializers so object graphs can be serialized automatically.

  • Field Details

    • NULL

      public static final byte NULL
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    • NOT_NULL

      public static final byte NOT_NULL
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    • REF

      private static final int REF
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    • NO_REF

      private static final int NO_REF
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    • defaultSerializer

      private SerializerFactory defaultSerializer

    • defaultSerializers

      private final ArrayList<Kryo.DefaultSerializerEntry> defaultSerializers

    • lowPriorityDefaultSerializerCount

      private final int lowPriorityDefaultSerializerCount

    • classResolver

      private final ClassResolver classResolver

    • nextRegisterID

      private int nextRegisterID

    • classLoader

      private ClassLoader classLoader

    • strategy

      private org.objenesis.strategy.InstantiatorStrategy strategy

    • registrationRequired

      private boolean registrationRequired

    • warnUnregisteredClasses

      private boolean warnUnregisteredClasses

    • depth

      private int depth

    • maxDepth

      private int maxDepth

    • autoReset

      private boolean autoReset

    • thread

      private volatile Thread thread

    • context

      private ObjectMap context

    • graphContext

      private ObjectMap graphContext

    • referenceResolver

      private ReferenceResolver referenceResolver

    • readReferenceIds

      private final IntArray readReferenceIds

    • references

      private boolean references

    • copyReferences

      private boolean copyReferences

    • readObject

      private Object readObject

    • copyDepth

      private int copyDepth

    • copyShallow

      private boolean copyShallow

    • originalToCopy

      private IdentityMap originalToCopy

    • needsCopyReference

      private Object needsCopyReference

    • genericsResolver

      private GenericsResolver genericsResolver

  • Constructor Details

  • Method Details

    • setDefaultSerializer

      public void setDefaultSerializer(SerializerFactory serializer)
      Sets the serializer factory to use when no default serializers match an object's type. Default is SerializerFactory.ReflectionSerializerFactory with FieldSerializer.
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    • setDefaultSerializer

      public void setDefaultSerializer(Class<? extends Serializer> serializer)
      Sets the serializer to use when no default serializers match an object's type. Default is FieldSerializer.
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    • addDefaultSerializer

      public void addDefaultSerializer(Class type, Serializer serializer)
      Instances of the specified class will use the specified serializer when register(Class) or register(Class, int) are called.
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    • addDefaultSerializer

      public void addDefaultSerializer(Class type, SerializerFactory serializerFactory)
      Instances of the specified class will use the specified factory to create a serializer when register(Class) or register(Class, int) are called.
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    • addDefaultSerializer

      public void addDefaultSerializer(Class type, Class<? extends Serializer> serializerClass)
      Instances of the specified class will use the specified serializer when register(Class) or register(Class, int) are called. Serializer instances are created as needed via SerializerFactory.ReflectionSerializerFactory.newSerializer(Kryo, Class, Class). By default, the following classes have a default serializer set:

      boolean Boolean byte Byte char
      Character short Short int Integer
      long Long float Float double
      Double String byte[] char[] short[]
      int[] long[] float[] double[] String[]
      Object[] Map BigInteger BigDecimal KryoSerializable
      Collection Date Collections.emptyList Collections.singleton Currency
      StringBuilder Enum Collections.emptyMap Collections.emptySet Calendar
      StringBuffer Class Collections.singletonList Collections.singletonMap TimeZone
      TreeMap EnumSet

      Note that the order default serializers are added is important for a class that may match multiple types. The above default serializers always have a lower priority than subsequent default serializers that are added.

    • getDefaultSerializer

      public Serializer getDefaultSerializer(Class type)
      Returns the best matching serializer for a class. This method can be overridden to implement custom logic to choose a serializer.

    • getDefaultSerializerForAnnotatedType

      protected Serializer getDefaultSerializerForAnnotatedType(Class type)

    • newDefaultSerializer

      protected Serializer newDefaultSerializer(Class type)
      Called by getDefaultSerializer(Class) when no default serializers matched the type. Subclasses can override this method to customize behavior. The default implementation calls SerializerFactory.newSerializer(Kryo, Class) using the default serializer.

    • register

      public Registration register(Class type)
      Registers the class using the lowest, next available integer ID and the default serializer. If the class is already registered, no change will be made and the existing registration will be returned. Registering a primitive also affects the corresponding primitive wrapper.

      Because the ID assigned is affected by the IDs registered before it, the order classes are registered is important when using this method. The order must be the same at deserialization as it was for serialization.

    • register

      public Registration register(Class type, int id)
      Registers the class using the specified ID and the default serializer. If the class is already registered this has no effect and the existing registration is returned. Registering a primitive also affects the corresponding primitive wrapper.

      IDs must be the same at deserialization as they were for serialization.

      Parameters:
      id - Must be >= 0. Smaller IDs are serialized more efficiently. IDs 0-8 are used by default for primitive types and String, but these IDs can be repurposed.

    • register

      public Registration register(Class type, Serializer serializer)
      Registers the class using the lowest, next available integer ID and the specified serializer. If the class is already registered, the existing entry is updated with the new serializer. Registering a primitive also affects the corresponding primitive wrapper.

      Because the ID assigned is affected by the IDs registered before it, the order classes are registered is important when using this method. The order must be the same at deserialization as it was for serialization.

    • register

      public Registration register(Class type, Serializer serializer, int id)
      Registers the class using the specified ID and serializer. Providing an ID that is already in use by the same type will cause the old entry to be overwritten. Registering a primitive also affects the corresponding primitive wrapper.

      IDs must be the same at deserialization as they were for serialization.

      Parameters:
      id - Must be >= 0. Smaller IDs are serialized more efficiently. IDs 0-9 are used by default for primitive types and their wrappers, String, and void, but these IDs can be repurposed.

    • register

      public Registration register(Registration registration)
      Stores the specified registration. If the ID is already in use by the same type, the old entry is overwritten. Registering a primitive also affects the corresponding primitive wrapper.

      IDs must be the same at deserialization as they were for serialization.

      Registration can be suclassed to efficiently store per type information, accessible in serializers via getRegistration(Class).

    • getNextRegistrationId

      public int getNextRegistrationId()
      Returns the lowest, next available integer ID.

    • getRegistration

      public Registration getRegistration(Class type)
      If the class is not registered and setRegistrationRequired(boolean) is false, it is automatically registered using the default serializer.
      Throws:
      IllegalArgumentException - if the class is not registered and setRegistrationRequired(boolean) is true.
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    • unregisteredClassMessage

      protected String unregisteredClassMessage(Class type)

    • getRegistration

      public Registration getRegistration(int classID)
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    • getSerializer

      public Serializer getSerializer(Class type)
      Returns the serializer for the registration for the specified class.
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    • writeClass

      public Registration writeClass(Output output, Class type)
      Writes a class and returns its registration.
      Parameters:
      type - May be null.
      Returns:
      Will be null if type is null.
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    • writeObject

      public void writeObject(Output output, Object object)
      Writes an object using the registered serializer.

    • writeObject

      public void writeObject(Output output, Object object, Serializer serializer)
      Writes an object using the specified serializer. The registered serializer is ignored.

    • writeObjectOrNull

      public void writeObjectOrNull(Output output, Object object, Class type)
      Writes an object or null using the registered serializer for the specified type.
      Parameters:
      object - May be null.

    • writeObjectOrNull

      public void writeObjectOrNull(Output output, Object object, Serializer serializer)
      Writes an object or null using the specified serializer. The registered serializer is ignored.
      Parameters:
      object - May be null.

    • writeClassAndObject

      public void writeClassAndObject(Output output, Object object)
      Writes the class and object or null using the registered serializer.
      Parameters:
      object - May be null.

    • writeReferenceOrNull

      boolean writeReferenceOrNull(Output output, Object object, boolean mayBeNull)
      Parameters:
      object - May be null if mayBeNull is true.
      Returns:
      true if no bytes need to be written for the object.

    • readClass

      public Registration readClass(Input input)
      Reads a class and returns its registration.
      Returns:
      May be null.
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    • readObject

      public <T> T readObject(Input input, Class<T> type)
      Reads an object using the registered serializer.

    • readObject

      public <T> T readObject(Input input, Class<T> type, Serializer serializer)
      Reads an object using the specified serializer. The registered serializer is ignored.

    • readObjectOrNull

      public <T> T readObjectOrNull(Input input, Class<T> type)
      Reads an object or null using the registered serializer.
      Returns:
      May be null.

    • readObjectOrNull

      public <T> T readObjectOrNull(Input input, Class<T> type, Serializer serializer)
      Reads an object or null using the specified serializer. The registered serializer is ignored.
      Returns:
      May be null.

    • readClassAndObject

      public Object readClassAndObject(Input input)
      Reads the class and object or null using the registered serializer.
      Returns:
      May be null.

    • readReferenceOrNull

      int readReferenceOrNull(Input input, Class type, boolean mayBeNull)
      Returns REF if a reference to a previously read object was read, which is stored in readObject. Returns a stack size (> 0) if a reference ID has been put on the stack.

    • reference

      public void reference(Object object)
      Called by Serializer.read(Kryo, Input, Class) and Serializer.copy(Kryo, Object) before Kryo can be used to deserialize or copy child objects. Calling this method is unnecessary if Kryo is not used to deserialize or copy child objects.
      Parameters:
      object - May be null, unless calling this method from Serializer.copy(Kryo, Object).

    • reset

      public void reset()
      Resets unregistered class names, references to previously serialized or deserialized objects, and the graph context. If auto reset is true, this method is called automatically when an object graph has been completely serialized or deserialized. If overridden, the super method must be called.

    • copy

      public <T> T copy(T object)
      Returns a deep copy of the object. Serializers for the classes involved must support Serializer.copy(Kryo, Object).
      Parameters:
      object - May be null.

    • copy

      public <T> T copy(T object, Serializer serializer)
      Returns a deep copy of the object using the specified serializer. Serializers for the classes involved must support Serializer.copy(Kryo, Object).
      Parameters:
      object - May be null.

    • copyShallow

      public <T> T copyShallow(T object)
      Returns a shallow copy of the object. Serializers for the classes involved must support Serializer.copy(Kryo, Object).
      Parameters:
      object - May be null.

    • copyShallow

      public <T> T copyShallow(T object, Serializer serializer)
      Returns a shallow copy of the object using the specified serializer. Serializers for the classes involved must support Serializer.copy(Kryo, Object).
      Parameters:
      object - May be null.

    • beginObject

      private void beginObject()

    • getClassResolver

      public ClassResolver getClassResolver()

    • getReferenceResolver

      public ReferenceResolver getReferenceResolver()
      Returns:
      May be null.

    • setClassLoader

      public void setClassLoader(ClassLoader classLoader)
      Sets the classloader to resolve unregistered class names to classes. The default is the loader that loaded the Kryo class.

    • getClassLoader

      public ClassLoader getClassLoader()

    • setRegistrationRequired

      public void setRegistrationRequired(boolean registrationRequired)
      If true, an exception is thrown when an unregistered class is encountered. Default is false.

      If false, when an unregistered class is encountered, its fully qualified class name will be serialized and the default serializer for the class used to serialize the object. Subsequent appearances of the class within the same object graph are serialized as an int id.

      Registered classes are serialized as an int id, avoiding the overhead of serializing the class name, but have the drawback of needing to know the classes to be serialized up front.

    • isRegistrationRequired

      public boolean isRegistrationRequired()

    • setWarnUnregisteredClasses

      public void setWarnUnregisteredClasses(boolean warnUnregisteredClasses)
      If true, kryo writes a warn log telling about the classes unregistered. Default is false.

      If false, no log are written when unregistered classes are encountered.

    • isWarnUnregisteredClasses

      public boolean isWarnUnregisteredClasses()

    • setReferences

      public boolean setReferences(boolean references)
      If true, each appearance of an object in the graph after the first is stored as an integer ordinal. When set to true, MapReferenceResolver is used. This enables references to the same object and cyclic graphs to be serialized, but typically adds overhead of one byte per object. Default is true.
      Returns:
      The previous value.

    • setCopyReferences

      public void setCopyReferences(boolean copyReferences)
      If true, when copy(Object) and other copy methods encounter an object for the first time the object is copied and on subsequent encounters the copied object is used. If false, the overhead of tracking which objects have already been copied is avoided because each object is copied every time it is encountered, however a stack overflow will occur if an object graph is copied that contains a circular reference. Default is true.

    • setReferenceResolver

      public void setReferenceResolver(ReferenceResolver referenceResolver)
      Sets the reference resolver and enables references.

    • getReferences

      public boolean getReferences()

    • setInstantiatorStrategy

      public void setInstantiatorStrategy(org.objenesis.strategy.InstantiatorStrategy strategy)
      Sets the strategy used by newInstantiator(Class) for creating objects. See StdInstantiatorStrategy to create objects via without calling any constructor. See SerializingInstantiatorStrategy to mimic Java's built-in serialization.
      Parameters:
      strategy - May be null.

    • getInstantiatorStrategy

      public org.objenesis.strategy.InstantiatorStrategy getInstantiatorStrategy()

    • newInstantiator

      protected org.objenesis.instantiator.ObjectInstantiator newInstantiator(Class type)
      Returns a new instantiator for creating new instances of the specified type. By default, an instantiator is returned that uses reflection if the class has a zero argument constructor, an exception is thrown. If a strategy is set, it will be used instead of throwing an exception.

    • newInstance

      public <T> T newInstance(Class<T> type)
      Creates a new instance of a class using Registration.getInstantiator(). If the registration's instantiator is null, a new one is set using newInstantiator(Class).

    • getContext

      public ObjectMap getContext()
      Name/value pairs that are available to all serializers.

    • getGraphContext

      public ObjectMap getGraphContext()
      Name/value pairs that are available to all serializers and are cleared after each object graph is serialized or deserialized.

    • getDepth

      public int getDepth()
      Returns the number of child objects away from the object graph root.

    • getOriginalToCopyMap

      public IdentityMap getOriginalToCopyMap()
      Returns the internal map of original to copy objects when a copy method is used. This can be used after a copy to map old objects to the copies, however it is cleared automatically by reset() so this is only useful when setAutoReset(boolean) is false.

    • setAutoReset

      public void setAutoReset(boolean autoReset)
      If true (the default), reset() is called automatically after an entire object graph has been read or written. If false, reset() must be called manually, which allows unregistered class names, references, and other information to span multiple object graphs.

    • setMaxDepth

      public void setMaxDepth(int maxDepth)
      Sets the maxiumum depth of an object graph. This can be used to prevent malicious data from causing a stack overflow. Default is Integer.MAX_VALUE.

    • isFinal

      public boolean isFinal(Class type)
      Returns true if the specified type is final. Final types can be serialized more efficiently because they are non-polymorphic.

      This can be overridden to force non-final classes to be treated as final. Eg, if an application uses ArrayList extensively but never uses an ArrayList subclass, treating ArrayList as final could allow FieldSerializer to save 1-2 bytes per ArrayList field.

    • isClosure

      protected boolean isClosure(Class type)
      Returns true if the specified type is a closure.

      This can be overridden to support alternative implementations of clousres. Current version supports Oracle's Java8 only

    • getGenericsResolver

      public GenericsResolver getGenericsResolver()