Class TaggedFieldSerializer<T>

java.lang.Object

com.esotericsoftware.kryo.Serializer<T>

com.esotericsoftware.kryo.serializers.FieldSerializer<T, TaggedFieldSerializerConfig>

com.esotericsoftware.kryo.serializers.TaggedFieldSerializer<T>

All Implemented Interfaces:

Comparator<FieldSerializer.CachedField>

public class TaggedFieldSerializer<T>
extends FieldSerializer<T, TaggedFieldSerializerConfig>

Serializes objects using direct field assignment for fields that have a @Tag(int) annotation. This provides backward compatibility so new fields can be added. TaggedFieldSerializer has two advantages over VersionFieldSerializer : 1) fields can be renamed and 2) fields marked with the @Deprecated annotation will be ignored when reading old bytes and won't be written to new bytes. Deprecation effectively removes the field from serialization, though the field and @Tag annotation must remain in the class. Deprecated fields can optionally be made private and/or renamed so they don't clutter the class (eg, ignored, ignored2). For these reasons, TaggedFieldSerializer generally provides more flexibility for classes to evolve. The downside is that it has a small amount of additional overhead compared to VersionFieldSerializer (an additional varint per field).

Forward compatibility is optionally supported by enabling TaggedFieldSerializerConfig.setSkipUnknownTags(boolean), which allows it to skip reading unknown tagged fields, which are presumably new fields added in future versions of an application. The data is only forward compatible if the newly added fields are tagged with TaggedFieldSerializer.Tag.annexed() set true, which comes with the cost of chunked encoding. When annexed fields are encountered during the read or write process of an object, a buffer is allocated to perform the chunked encoding.

Tag values must be entirely unique, even among a class and its superclass(es). An IllegalArgumentException will be thrown by Kryo.register(Class) (and its overloads) if duplicate Tag values are encountered.

See Also:

• VersionFieldSerializer

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static @interface	TaggedFieldSerializer.Tag	Marks a field for serialization.

Nested classes/interfaces inherited from class FieldSerializer

FieldSerializer.Bind, FieldSerializer.CachedField<X>, FieldSerializer.CachedFieldFactory, FieldSerializer.CachedFieldNameStrategy, FieldSerializer.Optional

Field Summary

Fields

Modifier and Type	Field	Description
private boolean[]	annexed
private boolean[]	deprecated
private static final Comparator<FieldSerializer.CachedField>	TAGGED_VALUE_COMPARATOR
private int[]	tags
private int	writeFieldCount

Fields inherited from class FieldSerializer

access, asmFieldFactory, componentType, config, kryo, objectFieldFactory, removedFields, type, typeParameters

Constructor Summary

Constructors

Constructor	Description
TaggedFieldSerializer(Kryo kryo, Class type)
TaggedFieldSerializer(Kryo kryo, Class type, TaggedFieldSerializerConfig config)

Method Summary

Modifier and Type	Method	Description
protected void	initializeCachedFields()
T	read(Kryo kryo, Input input, Class<T> type)	Reads bytes and returns a new object of the specified concrete type.
void	removeField(FieldSerializer.CachedField field)	Removes a field so that it won't be serialized.
void	removeField(String fieldName)	Removes a field so that it won't be serialized.
void	write(Kryo kryo, Output output, T object)	This method can be called for different fields having the same type.

Methods inherited from class FieldSerializer

compare, copy, create, createCopy, getCachedFieldName, getConfig, getCopyTransient, getField, getFields, getGenerics, getGenericsScope, getKryo, getSerializeTransient, getTransientFields, getType, newCachedField, newMatchingCachedField, rebuildCachedFields, rebuildCachedFields, setCopyTransient, setFieldsAsAccessible, setFieldsCanBeNull, setFixedFieldTypes, setGenerics, setIgnoreSyntheticFields, setOptimizedGenerics, setSerializeTransient

Methods inherited from class Serializer

getAcceptsNull, isImmutable, setAcceptsNull, setImmutable

Methods inherited from class Object

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

Methods inherited from interface Comparator

equals, reversed, thenComparing, thenComparing, thenComparing, thenComparingDouble, thenComparingInt, thenComparingLong

Field Details

tags

private int[] tags

writeFieldCount

private int writeFieldCount

deprecated

private boolean[] deprecated

annexed

private boolean[] annexed

TAGGED_VALUE_COMPARATOR

private static final Comparator<FieldSerializer.CachedField> TAGGED_VALUE_COMPARATOR

Constructor Details

TaggedFieldSerializer

public TaggedFieldSerializer(Kryo kryo,
 Class type)

TaggedFieldSerializer

public TaggedFieldSerializer(Kryo kryo,
 Class type,
 TaggedFieldSerializerConfig config)

Method Details

initializeCachedFields

protected void initializeCachedFields()

Overrides:

initializeCachedFields in class FieldSerializer<T, TaggedFieldSerializerConfig>

removeField

public void removeField(String fieldName)

Description copied from class: FieldSerializer

Removes a field so that it won't be serialized.

Overrides:

removeField in class FieldSerializer<T, TaggedFieldSerializerConfig>

removeField

public void removeField(FieldSerializer.CachedField field)

Description copied from class: FieldSerializer

Removes a field so that it won't be serialized.

Overrides:

removeField in class FieldSerializer<T, TaggedFieldSerializerConfig>

write

public void write(Kryo kryo,
 Output output,
 T object)

Description copied from class: FieldSerializer

This method can be called for different fields having the same type. Even though the raw type is the same, if the type is generic, it could happen that different concrete classes are used to instantiate it. Therefore, in case of different instantiation parameters, the fields analysis should be repeated. TODO: Cache serializer instances generated for a given set of generic parameters. Reuse it later instead of recomputing every time.

Overrides:

write in class FieldSerializer<T, TaggedFieldSerializerConfig>

Parameters:

object - May be null if Serializer.getAcceptsNull() is true.

read

public T read(Kryo kryo,
 Input input,
 Class<T> type)

Description copied from class: Serializer

Reads bytes and returns a new object of the specified concrete type.

Before Kryo can be used to read child objects, Kryo.reference(Object) must be called with the parent object to ensure it can be referenced by the child objects. Any serializer that uses Kryo to read a child object may need to be reentrant.

This method should not be called directly, instead this serializer can be passed to Kryo read methods that accept a serialier.

Overrides:

read in class FieldSerializer<T, TaggedFieldSerializerConfig>

Returns:

May be null if Serializer.getAcceptsNull() is true.