com.google.cloud.dataflow.sdk.coders

Class CoderRegistry

java.lang.Object

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

public class CoderRegistry
extends java.lang.Object

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.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	CoderRegistry.CoderFactory A factory for default Coders for values of a particular class.
class	CoderRegistry.ConstantCoderFactory A factory that always returns the coder with which it is instantiated.

Constructor Summary

Constructors

Constructor and Description
CoderRegistry()

Method Summary

Methods

Modifier and Type	Method and Description
<T,O> Coder<O>	getDefaultCoder(java.lang.Class<? extends T> subClass, java.lang.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,O> Coder<O>	getDefaultCoder(java.lang.Class<? extends T> subClass, java.lang.Class<T> baseClass, java.util.Map<java.lang.String,? extends Coder<?>> knownCoders, java.lang.String paramName) 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, otherwise returns null.
<I,O> Coder<O>	getDefaultCoder(com.google.common.reflect.TypeToken<O> typeToken, com.google.common.reflect.TypeToken<I> contextTypeToken, Coder<I> contextCoder) Returns the Coder to use by default for values of the given type, where the given context type uses the given context coder, or null if there is no default Coder.
<T> Coder<T>	getDefaultCoder(com.google.common.reflect.TypeToken<T> typeToken) Returns the Coder to use by default for values of the given type, or null if there is no default Coder.
<T> Coder<?>[]	getDefaultCoders(java.lang.Class<? extends T> subClass, java.lang.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> java.util.Map<java.lang.String,Coder<?>>	getDefaultCoders(java.lang.Class<? extends T> subClass, java.lang.Class<T> baseClass, java.util.Map<java.lang.String,? 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.
<I,O> Coder<O>	getDefaultOutputCoder(SerializableFunction<I,O> fn, Coder<I> inputCoder) Returns the Coder to use on elements produced by this function, given the coder used for its input elements.
void	registerCoder(java.lang.Class<?> clazz, java.lang.Class<?> coderClazz) Registers coderClazz as the default Coder<T> class to handle encoding and decoding instances of clazz of type T.
void	registerCoder(java.lang.Class<?> rawClazz, Coder<?> coder)
void	registerCoder(java.lang.Class<?> rawClazz, CoderRegistry.CoderFactory coderFactory)
void	registerStandardCoders() Registers standard Coders with this CoderRegistry.

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(java.lang.Class<?> clazz,
                 java.lang.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(java.lang.Class<?> rawClazz,
                 CoderRegistry.CoderFactory coderFactory)

registerCoder

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

getDefaultCoder

public <T> Coder<T> getDefaultCoder(com.google.common.reflect.TypeToken<T> typeToken)

Returns the Coder to use by default for values of the given type, or null if there is no default Coder.

getDefaultCoder

public <I,O> Coder<O> getDefaultCoder(com.google.common.reflect.TypeToken<O> typeToken,
                             com.google.common.reflect.TypeToken<I> contextTypeToken,
                             Coder<I> contextCoder)

Returns the Coder to use by default for values of the given type, where the given context type uses the given context coder, or null if there is no default Coder.

getDefaultOutputCoder

public <I,O> Coder<O> getDefaultOutputCoder(SerializableFunction<I,O> fn,
                                   Coder<I> inputCoder)

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

getDefaultCoder

public <T,O> Coder<O> getDefaultCoder(java.lang.Class<? extends T> subClass,
                             java.lang.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).

getDefaultCoder

public <T,O> Coder<O> getDefaultCoder(java.lang.Class<? extends T> subClass,
                             java.lang.Class<T> baseClass,
                             java.util.Map<java.lang.String,? extends Coder<?>> knownCoders,
                             java.lang.String paramName)

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).

getDefaultCoder

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

Returns the Coder to use for the provided example value, if it can be determined, otherwise returns null. If more than one default coder matches, this will raise an exception.

getDefaultCoders

public <T> java.util.Map<java.lang.String,Coder<?>> getDefaultCoders(java.lang.Class<? extends T> subClass,
                                                            java.lang.Class<T> baseClass,
                                                            java.util.Map<java.lang.String,? 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.

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 which will be used to infer the others.

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(java.lang.Class<? extends T> subClass,
                              java.lang.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.

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 which will be used to infer the others.

If a type cannot be inferred, null is returned.

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:

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