com.esotericsoftware.kryo

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.

Author:

Nathan Sweet

Field Summary

Fields

Modifier and Type	Field and Description
static byte	NOT_NULL
static byte	NULL

Constructor Summary

Constructors

Constructor and Description
Kryo() Creates a new Kryo with a DefaultClassResolver and a MapReferenceResolver.
Kryo(ClassResolver classResolver, ReferenceResolver referenceResolver)
Kryo(ReferenceResolver referenceResolver) Creates a new Kryo with a DefaultClassResolver.

Method Summary

Methods

Modifier and Type	Method and Description
void	addDefaultSerializer(Class type, Class<? extends Serializer> serializerClass) Instances of the specified class will use the specified serializer.
void	addDefaultSerializer(Class type, Serializer serializer) Instances of the specified class will use the specified serializer.
<T> T	copy(T object) Returns a deep copy of the object.
<T> T	copy(T object, Serializer serializer) Returns a deep copy of the object using the specified serializer.
<T> T	copyShallow(T object) Returns a shallow copy of the object.
<T> T	copyShallow(T object, Serializer serializer) Returns a shallow copy of the object using the specified serializer.
ClassLoader	getClassLoader()
ClassResolver	getClassResolver()
ObjectMap	getContext() Name/value pairs that are available to all serializers.
Serializer	getDefaultSerializer(Class type) Returns the best matching serializer for a class.
int	getDepth() Returns the number of child objects away from the object graph root.
static Class[]	getGenerics(Type genericType) Returns the first level of classes or interfaces for a generic type.
ObjectMap	getGraphContext() Name/value pairs that are available to all serializers and are cleared after each object graph is serialized or deserialized.
int	getNextRegistrationId() Returns the lowest, next available integer ID.
ReferenceResolver	getReferenceResolver()
boolean	getReferences()
Registration	getRegistration(Class type)
Registration	getRegistration(int classID)
Serializer	getSerializer(Class type) Returns the serializer for the registration for the specified class.
boolean	isFinal(Class type) Returns true if the specified type is final.
boolean	isRegistrationRequired()
protected Serializer	newDefaultSerializer(Class type) Called by getDefaultSerializer(Class) when no default serializers matched the type.
<T> T	newInstance(Class<T> type) Creates a new instance of a class using Registration.getInstantiator().
protected org.objenesis.instantiator.ObjectInstantiator	newInstantiator(Class type) Returns a new instantiator for creating new instances of the specified type.
Serializer	newSerializer(Class<? extends Serializer> serializerClass, Class type) Creates a new instance of the specified serializer for serializing the specified class.
Registration	readClass(Input input) Reads a class and returns its registration.
Object	readClassAndObject(Input input) Reads the class and object or null using the registered serializer.
<T> T	readObject(Input input, Class<T> type) Reads an object using the registered serializer.
<T> T	readObject(Input input, Class<T> type, Serializer serializer) Reads an object using the specified serializer.
<T> T	readObjectOrNull(Input input, Class<T> type) Reads an object or null using the registered serializer.
<T> T	readObjectOrNull(Input input, Class<T> type, Serializer serializer) Reads an object or null using the specified serializer.
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.
Registration	register(Class type) Registers the class using the lowest, next available integer ID and the default serializer.
Registration	register(Class type, int id) Registers the class using the specified ID and the default serializer.
Registration	register(Class type, Serializer serializer) Registers the class using the lowest, next available integer ID and the specified serializer.
Registration	register(Class type, Serializer serializer, int id) Registers the class using the specified ID and serializer.
Registration	register(Registration registration) Stores the specified registration.
void	reset() Resets unregistered class names.
void	setAutoReset(boolean autoReset) If true (the default), reset() is called automatically after an entire object graph has been read or written.
void	setClassLoader(ClassLoader classLoader) Sets the classloader to resolve unregistered class names to classes.
void	setDefaultSerializer(Class<? extends Serializer> serializer) Sets the serailzer to use when no default serializers match an object's type.
void	setInstantiatorStrategy(org.objenesis.strategy.InstantiatorStrategy strategy) Sets the strategy used by newInstantiator(Class) for creating objects.
void	setMaxDepth(int maxDepth) Sets the maxiumum depth of an object graph.
void	setReferenceResolver(ReferenceResolver referenceResolver) Sets the reference resolver and enables references.
boolean	setReferences(boolean references) If true, each appearance of an object in the graph after the first is stored as an integer ordinal.
void	setRegistrationRequired(boolean registrationRequired) If true, an exception is thrown when an unregistered class is encountered.
Registration	writeClass(Output output, Class type) Writes a class and returns its registration.
void	writeClassAndObject(Output output, Object object) Writes the class and object or null using the registered serializer.
void	writeObject(Output output, Object object) Writes an object using the registered serializer.
void	writeObject(Output output, Object object, Serializer serializer) Writes an object using the specified serializer.
void	writeObjectOrNull(Output output, Object object, Class type) Writes an object or null using the registered serializer for the specified type.
void	writeObjectOrNull(Output output, Object object, Serializer serializer) Writes an object or null using the specified serializer.

Methods inherited from class java.lang.Object

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

Field Detail

NULL

public static final byte NULL

See Also:

Constant Field Values

NOT_NULL

public static final byte NOT_NULL

See Also:

Constant Field Values

Constructor Detail

Kryo

public Kryo()

Creates a new Kryo with a DefaultClassResolver and a MapReferenceResolver.

Kryo

public Kryo(ReferenceResolver referenceResolver)

Creates a new Kryo with a DefaultClassResolver.

Parameters:

referenceResolver - May be null to disable references.

Kryo

public Kryo(ClassResolver classResolver,
    ReferenceResolver referenceResolver)

Parameters:

referenceResolver - May be null to disable references.

Method Detail

setDefaultSerializer

public void setDefaultSerializer(Class<? extends Serializer> serializer)

Sets the serailzer to use when no default serializers match an object's type. Default is FieldSerializer.

See Also:

newDefaultSerializer(Class)

addDefaultSerializer

public void addDefaultSerializer(Class type,
                        Serializer serializer)

Instances of the specified class will use the specified serializer.

See Also:

setDefaultSerializer(Class)

addDefaultSerializer

public void addDefaultSerializer(Class type,
                        Class<? extends Serializer> serializerClass)

Instances of the specified class will use the specified serializer. Serializer instances are created as needed via newSerializer(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.

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 newSerializer(Class, Class) using the default serializer.

newSerializer

public Serializer newSerializer(Class<? extends Serializer> serializerClass,
                       Class type)

Creates a new instance of the specified serializer for serializing the specified class. Serializers must have a zero argument constructor or one that takes (Kryo), (Class), or (Kryo, Class).

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, 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,
                    int id)

Registers the class using the specified ID and the default serializer. If the ID is already in use by the same type, the old entry is overwritten. If the ID is already in use by a different type, a KryoException is thrown. 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.

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. If the ID is already in use by the same type, the old entry is overwritten. If the ID is already in use by a different type, a KryoException is thrown. 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.

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. If the ID is already in use by a different type, a KryoException is thrown. 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)

Throws:

IllegalArgumentException - if the class is not registered and setRegistrationRequired(boolean) is true.

See Also:

ClassResolver.getRegistration(Class)

getRegistration

public Registration getRegistration(int classID)

See Also:

ClassResolver.getRegistration(int)

getSerializer

public Serializer getSerializer(Class type)

Returns the serializer for the registration for the specified class.

See Also:

getRegistration(Class), Registration.getSerializer()

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.

See Also:

ClassResolver.writeClass(Output, Class)

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.

readClass

public Registration readClass(Input input)

Reads a class and returns its registration.

Returns:

May be null.

See Also:

ClassResolver.readClass(Input)

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.

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.

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()

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.

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.

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.

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.

getGenerics

public static Class[] getGenerics(Type genericType)

Returns the first level of classes or interfaces for a generic type.

Returns:

null if the specified type is not generic or its generic types are not classes.