org.apache.beam.sdk.coders

Class ListCoder<T>

java.lang.Object

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

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

org.apache.beam.sdk.coders.IterableLikeCoder<T,java.util.List<T>>

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

Type Parameters:

T - the type of the elements of the Lists being transcoded

All Implemented Interfaces:

java.io.Serializable

public class ListCoder<T>
extends IterableLikeCoder<T,java.util.List<T>>

A Coder for List, using the format of IterableLikeCoder.

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	ListCoder(Coder<T> elemCoder)

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).
protected java.util.List<T>	decodeToIterable(java.util.List<T> decodedElements) Builds an instance of IterableT, this coder's associated Iterable-like subtype, from a list of decoded elements.
TypeDescriptor<java.util.List<T>>	getEncodedTypeDescriptor() Returns the TypeDescriptor for the type encoded.
static <T> ListCoder<T>	of(Coder<T> elemCoder)
java.lang.Object	structuralValue(java.util.List<T> values) Returns an object with an Object.equals() method that represents structural equality on the argument.
void	verifyDeterministic() List sizes are always known, so ListIterable may be deterministic while the general IterableLikeCoder is not.

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

decode, decodeToIterable, encode, getCoderArguments, getElemCoder, isRegisterByteSizeObserverCheap, registerByteSizeObserver

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

equals, getComponents, hashCode, toString

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

decode, encode, getEncodedElementByteSize, verifyDeterministic, verifyDeterministic

Methods inherited from class java.lang.Object

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

Constructor Detail

ListCoder

protected ListCoder(Coder<T> elemCoder)

Method Detail

of

public static <T> ListCoder<T> of(Coder<T> elemCoder)

decodeToIterable

protected final java.util.List<T> decodeToIterable(java.util.List<T> decodedElements)

Description copied from class: IterableLikeCoder

Builds an instance of IterableT, this coder's associated Iterable-like subtype, from a list of decoded elements.

Override IterableLikeCoder.decodeToIterable(List, long, InputStream) if you need access to the terminator value and the InputStream.

Specified by:

decodeToIterable in class IterableLikeCoder<T,java.util.List<T>>

consistentWithEquals

public boolean consistentWithEquals()

Description copied from class: Coder

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<java.util.List<T>>

structuralValue

public java.lang.Object structuralValue(java.util.List<T> values)

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(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<java.util.List<T>>

verifyDeterministic

public void verifyDeterministic()
                         throws Coder.NonDeterministicException

List sizes are always known, so ListIterable may be deterministic while the general IterableLikeCoder is not.

Overrides:

verifyDeterministic in class IterableLikeCoder<T,java.util.List<T>>

Throws:

Coder.NonDeterministicException - if this coder is not deterministic.

getEncodedTypeDescriptor

public TypeDescriptor<java.util.List<T>> getEncodedTypeDescriptor()

Description copied from class: Coder

Returns the TypeDescriptor for the type encoded.

Overrides:

getEncodedTypeDescriptor in class Coder<java.util.List<T>>