com.google.cloud.dataflow.sdk.coders

Class CoderRegistry

java.lang.Object

com.google.cloud.dataflow.sdk.coders.CoderRegistry

All Implemented Interfaces:

CoderProvider

public class CoderRegistry
extends Object
implements CoderProvider

A CoderRegistry allows registering the default Coder to use for a Java class, and looking up and instantiating the default Coder for a Java type.

CoderRegistry uses the following mechanisms to determine a default Coder for a Java class, in order of precedence:

• Registration: coders can be registered explicitly via registerCoder(java.lang.Class<?>, java.lang.Class<?>). Built-in types are registered via registerStandardCoders().
• Annotations: DefaultCoder can be used to annotate a type with the default Coder type.
• Inheritance: Serializable objects are given a default Coder of SerializableCoder.

Constructor Summary

Constructors

Constructor and Description
CoderRegistry()

Method Summary

Methods

Modifier and Type	Method and Description
<T> Coder<T>	getCoder(TypeDescriptor<T> typeDescriptor) See getDefaultCoder(TypeDescriptor).
<T,OutputT> Coder<OutputT>	getDefaultCoder(Class<? extends T> subClass, Class<T> baseClass, Coder<?>... knownCoders) Returns the Coder to use for the last type parameter specialization of the subclass given Coders to use for all other type parameters specializations (if any).
<T,OutputT> Coder<OutputT>	getDefaultCoder(Class<? extends T> subClass, Class<T> baseClass, Map<Type,? extends Coder<?>> knownCoders, TypeVariable<?> param) Returns the Coder to use for the specified type parameter specialization of the subclass, given Coders to use for all other type parameters (if any).
<T> Coder<T>	getDefaultCoder(T exampleValue) Returns the Coder to use for the provided example value, if it can be determined.
<InputT,OutputT> Coder<OutputT>	getDefaultCoder(TypeDescriptor<OutputT> typeDescriptor, TypeDescriptor<InputT> contextTypeDescriptor, Coder<InputT> contextCoder) Returns the Coder to use by default for values of the given type, where the given context type uses the given context coder.
<T> Coder<T>	getDefaultCoder(TypeDescriptor<T> typeDescriptor) Returns the Coder to use by default for values of the given type.
<T> Coder<?>[]	getDefaultCoders(Class<? extends T> subClass, Class<T> baseClass, Coder<?>[] knownCoders) Returns an array listing, for each of baseClass's type parameters, the Coder to use by default for it, in the context of subClass's specialization of baseClass.
<T> Map<Type,Coder<?>>	getDefaultCoders(Class<? extends T> subClass, Class<T> baseClass, Map<Type,? extends Coder<?>> knownCoders) Returns a Map from each of baseClass's type parameters to the Coder to use by default for it, in the context of subClass's specialization of baseClass.
<InputT,OutputT> Coder<OutputT>	getDefaultOutputCoder(SerializableFunction<InputT,OutputT> fn, Coder<InputT> inputCoder) Returns the Coder to use on elements produced by this function, given the coder used for its input elements.
CoderProvider	getFallbackCoderProvider()
void	registerCoder(Class<?> clazz, Class<?> coderClazz) Registers coderClazz as the default Coder<T> class to handle encoding and decoding instances of clazz of type T.
void	registerCoder(Class<?> rawClazz, Coder<?> coder)
void	registerCoder(Class<?> rawClazz, CoderFactory coderFactory)
void	registerStandardCoders() Registers standard Coders with this CoderRegistry.
void	setFallbackCoderProvider(CoderProvider coderProvider)

Methods inherited from class java.lang.Object

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

Constructor Detail

CoderRegistry

public CoderRegistry()

Method Detail

registerStandardCoders

public void registerStandardCoders()

Registers standard Coders with this CoderRegistry.

registerCoder

public void registerCoder(Class<?> clazz,
                 Class<?> coderClazz)

Registers coderClazz as the default Coder<T> class to handle encoding and decoding instances of clazz of type T.

coderClazz should have a static factory method with the following signature:

 public static Coder<T> of(Coder<X> argCoder1, Coder<Y> argCoder2, ...)
  

This method will be called to create instances of Coder<T> for values of type T, passing Coders for each of the generic type parameters of T. If T takes no generic type parameters, then the of() factory method should have no arguments.

If T is a parameterized type, then it should additionally have a method with the following signature:

 public static List<Object> getInstanceComponents(T exampleValue);
  

This method will be called to decompose a value during the coder inference process, to automatically choose coders for the components

registerCoder

public void registerCoder(Class<?> rawClazz,
                 CoderFactory coderFactory)

registerCoder

public void registerCoder(Class<?> rawClazz,
                 Coder<?> coder)

getDefaultCoder

public <T> Coder<T> getDefaultCoder(TypeDescriptor<T> typeDescriptor)
                         throws CannotProvideCoderException

Returns the Coder to use by default for values of the given type.

Throws:

CannotProvideCoderException - if there is no default Coder.

getCoder

public <T> Coder<T> getCoder(TypeDescriptor<T> typeDescriptor)
                  throws CannotProvideCoderException

See getDefaultCoder(TypeDescriptor).

Specified by:

getCoder in interface CoderProvider

Throws:

CannotProvideCoderException - if no coder can be provided

getDefaultCoder

public <InputT,OutputT> Coder<OutputT> getDefaultCoder(TypeDescriptor<OutputT> typeDescriptor,
                                              TypeDescriptor<InputT> contextTypeDescriptor,
                                              Coder<InputT> contextCoder)
                               throws CannotProvideCoderException

Returns the Coder to use by default for values of the given type, where the given context type uses the given context coder.

Throws:

CannotProvideCoderException - if there is no default Coder.

getDefaultOutputCoder

public <InputT,OutputT> Coder<OutputT> getDefaultOutputCoder(SerializableFunction<InputT,OutputT> fn,
                                                    Coder<InputT> inputCoder)
                                     throws CannotProvideCoderException

Returns the Coder to use on elements produced by this function, given the coder used for its input elements.

Throws:

CannotProvideCoderException

getDefaultCoder

public <T,OutputT> Coder<OutputT> getDefaultCoder(Class<? extends T> subClass,
                                         Class<T> baseClass,
                                         Coder<?>... knownCoders)
                               throws CannotProvideCoderException

Returns the Coder to use for the last type parameter specialization of the subclass given Coders to use for all other type parameters specializations (if any).

Throws:

CannotProvideCoderException - if there is no default Coder.

getDefaultCoder

public <T,OutputT> Coder<OutputT> getDefaultCoder(Class<? extends T> subClass,
                                         Class<T> baseClass,
                                         Map<Type,? extends Coder<?>> knownCoders,
                                         TypeVariable<?> param)
                               throws CannotProvideCoderException

Returns the Coder to use for the specified type parameter specialization of the subclass, given Coders to use for all other type parameters (if any).

Throws:

CannotProvideCoderException - if there is no default Coder.

getDefaultCoder

public <T> Coder<T> getDefaultCoder(T exampleValue)
                         throws CannotProvideCoderException

Returns the Coder to use for the provided example value, if it can be determined.

Throws:

CannotProvideCoderException - if there is no default Coder or more than one coder matches

getDefaultCoders

public <T> Map<Type,Coder<?>> getDefaultCoders(Class<? extends T> subClass,
                                      Class<T> baseClass,
                                      Map<Type,? extends Coder<?>> knownCoders)

Returns a Map from each of baseClass's type parameters to the Coder to use by default for it, in the context of subClass's specialization of baseClass.

If no coder can be inferred for a particular type parameter, then that type variable will be absent from the returned map.

For example, if baseClass is Map.class and subClass extends Map<String, Integer> then this will return the registered Coders to use for String and Integer as a {"K": stringCoder, "V": intCoder} Map. The knownCoders parameter can be used to provide known coders for any of the parameters that will be used to infer the others.

Note that inference is attempted for every type variable. For a type MyType<One, Two, Three> inference will will be attempted for all of One, Two, Three, even if the requester only wants a coder for Two.

For this reason, getDefaultCoders (plural) does not throw an exception if a coder for a particular type variable cannot be inferred. Instead, it is left absent from the map. It is the responsibility of the caller (usually getDefaultCoder(com.google.cloud.dataflow.sdk.values.TypeDescriptor<T>) to extract the desired coder or throw a CannotProvideCoderException when appropriate.

Parameters:

subClass - the concrete type whose specializations are being inferred

baseClass - the base type, a parameterized class

knownCoders - a map corresponding to the set of known coders indexed by parameter name

getDefaultCoders

public <T> Coder<?>[] getDefaultCoders(Class<? extends T> subClass,
                              Class<T> baseClass,
                              Coder<?>[] knownCoders)

Returns an array listing, for each of baseClass's type parameters, the Coder to use by default for it, in the context of subClass's specialization of baseClass.

If a coder cannot be inferred for a type variable, its slot in the resulting array will be null.

For example, if baseClass is Map.class and subClass extends Map<String, Integer> then this will return the registered Coders to use for String and Integer, in that order. The knownCoders parameter can be used to provide known coders for any of the parameters that will be used to infer the others.

Note that inference is attempted for every type variable. For a type MyType<One, Two, Three> inference will will be attempted for all of One, Two, Three, even if the requester only wants a coder for Two.

For this reason getDefaultCoders (plural) does not throw an exception if a coder for a particular type variable cannot be inferred. Instead, it results in a null in the array. It is the responsibility of the caller (usually getDefaultCoder(com.google.cloud.dataflow.sdk.values.TypeDescriptor<T>) to extract the desired coder or throw a CannotProvideCoderException when appropriate.

Parameters:

subClass - the concrete type whose specializations are being inferred

baseClass - the base type, a parameterized class

knownCoders - an array corresponding to the set of base class type parameters. Each entry is can be either a Coder (in which case it will be used for inference) or null (in which case it will be inferred). May be null to indicate the entire set of parameters should be inferred.

Throws:

IllegalArgumentException - if baseClass doesn't have type parameters or if the length of knownCoders is not equal to the number of type parameters

setFallbackCoderProvider

public void setFallbackCoderProvider(CoderProvider coderProvider)

getFallbackCoderProvider

public CoderProvider getFallbackCoderProvider()