com.google.cloud.dataflow.sdk.coders

Interface Coder<T>

Type Parameters:

T - the type of the values being transcoded

All Superinterfaces:

java.io.Serializable

All Known Implementing Classes:

AtomicCoder, AvroCoder, BigEndianIntegerCoder, BigEndianLongCoder, ByteArrayCoder, CoGbkResult.CoGbkResultCoder, CollectionCoder, CustomCoder, DelegateCoder, DoubleCoder, EntityCoder, GlobalWindow.Coder, InstantCoder, IterableCoder, IterableLikeCoder, KvCoder, KvCoderBase, ListCoder, MapCoder, MapCoderBase, SerializableCoder, SetCoder, StandardCoder, StringDelegateCoder, StringUtf8Coder, TableRowJsonCoder, TextualIntegerCoder, TimestampedValue.TimestampedValueCoder, VarIntCoder, VarLongCoder, VoidCoder

public interface Coder<T>
extends java.io.Serializable

A Coder<T> defines how to encode and decode values of type T into byte streams.

All methods of a Coder<T> are required to be thread safe.

Coders are serialized during job creation and deserialized before use, via JSON serialization.

See SerializableCoder for an example of a Coder that adds a custom field to the Coder serialization. It provides a constructor annotated with JsonCreator, which is a factory method used when deserializing a Coder instance.

See KvCoder for an example of a nested Coder type.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	Coder.Context The context in which encoding or decoding is being done.
static class	Coder.NonDeterministicException Exception thrown by verifyDeterministic() if the encoding is not deterministic.

Method Summary

Methods

Modifier and Type	Method and Description
com.google.cloud.dataflow.sdk.util.CloudObject	asCloudObject() Returns the CloudObject that represents this Coder.
T	decode(java.io.InputStream inStream, Coder.Context context) Decodes a value of type T from the given input stream in the given context.
void	encode(T value, java.io.OutputStream outStream, Coder.Context context) Encodes the given value of type T onto the given output stream in the given context.
java.util.List<? extends Coder<?>>	getCoderArguments() If this is a Coder for a parameterized type, returns the list of Coders being used for each of the parameters, or returns null if this cannot be done or this is not a parameterized type.
boolean	isDeterministic() Deprecated. verifyDeterministic() should be used instead to produce explanations of why a given Coder is non-deterministic.
boolean	isRegisterByteSizeObserverCheap(T value, Coder.Context context) Returns whether registerByteSizeObserver(T, com.google.cloud.dataflow.sdk.util.common.ElementByteSizeObserver, com.google.cloud.dataflow.sdk.coders.Coder.Context) cheap enough to call for every element, that is, if this Coder can calculate the byte size of the element to be coded in roughly constant time (or lazily).
void	registerByteSizeObserver(T value, com.google.cloud.dataflow.sdk.util.common.ElementByteSizeObserver observer, Coder.Context context) Notifies the ElementByteSizeObserver about the byte size of the encoded value using this Coder.
void	verifyDeterministic() Throw Coder.NonDeterministicException if the coding is not deterministic.

Method Detail

encode

void encode(T value,
          java.io.OutputStream outStream,
          Coder.Context context)
            throws CoderException,
                   java.io.IOException

Encodes the given value of type T onto the given output stream in the given context.

Throws:

java.io.IOException - if writing to the OutputStream fails for some reason

CoderException - if the value could not be encoded for some reason

decode

T decode(java.io.InputStream inStream,
       Coder.Context context)
         throws CoderException,
                java.io.IOException

Decodes a value of type T from the given input stream in the given context. Returns the decoded value.

Throws:

java.io.IOException - if reading from the InputStream fails for some reason

CoderException - if the value could not be decoded for some reason

getCoderArguments

java.util.List<? extends Coder<?>> getCoderArguments()

If this is a Coder for a parameterized type, returns the list of Coders being used for each of the parameters, or returns null if this cannot be done or this is not a parameterized type.

asCloudObject

com.google.cloud.dataflow.sdk.util.CloudObject asCloudObject()

Returns the CloudObject that represents this Coder.

isDeterministic

@Deprecated
boolean isDeterministic()

Deprecated. verifyDeterministic() should be used instead to produce explanations of why a given Coder is non-deterministic.

Returns true if the coding is deterministic.

In order for a Coder to be considered deterministic, the following must be true:

• two values which compare as equal (via Object.equals() or Comparable.compareTo(), if supported), have the same encoding.
• the Coder always produces a canonical encoding, which is the same for an instance of an object even if produced on different computers at different times.

verifyDeterministic

void verifyDeterministic()
                         throws Coder.NonDeterministicException

Throw Coder.NonDeterministicException if the coding is not deterministic.

In order for a Coder to be considered deterministic, the following must be true:

• two values which compare as equal (via Object.equals() or Comparable.compareTo(), if supported), have the same encoding.
• the Coder always produces a canonical encoding, which is the same for an instance of an object even if produced on different computers at different times.

Throws:

Coder.NonDeterministicException - if this coder is not deterministic.

isRegisterByteSizeObserverCheap

boolean isRegisterByteSizeObserverCheap(T value,
                                      Coder.Context context)

Returns whether registerByteSizeObserver(T, com.google.cloud.dataflow.sdk.util.common.ElementByteSizeObserver, com.google.cloud.dataflow.sdk.coders.Coder.Context) cheap enough to call for every element, that is, if this Coder can calculate the byte size of the element to be coded in roughly constant time (or lazily).

Not intended to be called by user code, but instead by PipelineRunner implementations.

registerByteSizeObserver

void registerByteSizeObserver(T value,
                            com.google.cloud.dataflow.sdk.util.common.ElementByteSizeObserver observer,
                            Coder.Context context)
                              throws java.lang.Exception

Notifies the ElementByteSizeObserver about the byte size of the encoded value using this Coder.

Not intended to be called by user code, but instead by PipelineRunner implementations.

Throws:

java.lang.Exception