org.apache.beam.sdk.coders

Class StructuredCoder<T>

java.lang.Object

org.apache.beam.sdk.coders.Coder<T>

org.apache.beam.sdk.coders.StructuredCoder<T>

All Implemented Interfaces:

java.io.Serializable

Direct Known Subclasses:

AtomicCoder, FileBasedSink.FileResultCoder, GlobalWindow.Coder, IntervalWindow.IntervalWindowCoder, IterableLikeCoder, KafkaRecordCoder, KvCoder, LengthPrefixCoder, MapCoder, NullableCoder, TimestampedValue.TimestampedValueCoder, UnionCoder, ValueInSingleWindow.Coder, ValueWithRecordId.ValueWithRecordIdCoder, VarLongCoder

public abstract class StructuredCoder<T>
extends Coder<T>

An abstract base class to implement a Coder that defines equality, hashing, and printing via the class name and recursively using getComponents().

A StructuredCoder should be defined purely in terms of its component coders, and contain no additional configuration.

To extend StructuredCoder, override the following methods as appropriate:

• getComponents(): the default implementation returns Coder.getCoderArguments().
• Coder.getEncodedElementByteSize(T) and Coder.isRegisterByteSizeObserverCheap(T): the default implementation encodes values to bytes and counts the bytes, which is considered expensive. The default element byte size observer uses the value returned by Coder.getEncodedElementByteSize(T).

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.beam.sdk.coders.Coder

Coder.Context, Coder.NonDeterministicException

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	StructuredCoder()

Method Summary

Modifier and Type	Method and Description
boolean	consistentWithEquals() Returns true if this Coder is injective with respect to Object.equals(java.lang.Object).
boolean	equals(java.lang.Object o)
java.util.List<? extends Coder<?>>	getComponents() Returns the list of Coders that are components of this Coder.
TypeDescriptor<T>	getEncodedTypeDescriptor() Returns the TypeDescriptor for the type encoded.
int	hashCode()
java.lang.Object	structuralValue(T value) Returns an object with an Object.equals() method that represents structural equality on the argument.
java.lang.String	toString()

Methods inherited from class org.apache.beam.sdk.coders.Coder

decode, decode, encode, encode, getCoderArguments, getEncodedElementByteSize, isRegisterByteSizeObserverCheap, registerByteSizeObserver, verifyDeterministic, verifyDeterministic, verifyDeterministic

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

StructuredCoder

protected StructuredCoder()

Method Detail

getComponents

public java.util.List<? extends Coder<?>> getComponents()

Returns the list of Coders that are components of this Coder.

The default components will be equal to the value returned by Coder.getCoderArguments().

equals

public boolean equals(java.lang.Object o)

Overrides:

equals in class java.lang.Object

Returns:

true if the two StructuredCoder instances have the same class and equal components.

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

consistentWithEquals

public boolean consistentWithEquals()

Returns true if this Coder is injective with respect to Object.equals(java.lang.Object).

Whenever the encoded bytes of two values are equal, then the original values are equal according to Objects.equals(). Note that this is well-defined for null.

This condition is most notably false for arrays. More generally, this condition is false whenever equals() compares object identity, rather than performing a semantic/structural comparison.

By default, returns false.

Overrides:

consistentWithEquals in class Coder<T>

Returns:

false for StructuredCoder unless overridden.

structuralValue

public java.lang.Object structuralValue(T value)

Description copied from class: Coder

Returns an object with an Object.equals() method that represents structural equality on the argument.

For any two values x and y of type T, if their encoded bytes are the same, then it must be the case that structuralValue(x).equals(@code structuralValue(y).

Most notably:

• The structural value for an array coder should perform a structural comparison of the contents of the arrays, rather than the default behavior of comparing according to object identity.
• The structural value for a coder accepting null should be a proper object with an equals() method, even if the input value is null.

See also Coder.consistentWithEquals().

By default, if this coder is Coder.consistentWithEquals(), and the value is not null, returns the provided object. Otherwise, encodes the value into a byte[], and returns an object that performs array equality on the encoded bytes.

Overrides:

structuralValue in class Coder<T>

getEncodedTypeDescriptor

public TypeDescriptor<T> getEncodedTypeDescriptor()

Description copied from class: Coder

Returns the TypeDescriptor for the type encoded.

Overrides:

getEncodedTypeDescriptor in class Coder<T>