org.apache.beam.sdk.coders

Class VoidCoder

java.lang.Object

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

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

org.apache.beam.sdk.coders.AtomicCoder<java.lang.Void>

org.apache.beam.sdk.coders.VoidCoder

All Implemented Interfaces:

java.io.Serializable

public class VoidCoder
extends AtomicCoder<java.lang.Void>

A Coder for Void. Uses zero bytes per Void.

See Also:

Serialized Form

Nested Class Summary

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

Coder.Context, Coder.NonDeterministicException

Method Summary

Modifier and Type	Method and Description
@Nullable java.lang.Void	decode(java.io.InputStream inStream) Decodes a value of type T from the given input stream in the given context.
void	encode(java.lang.Void value, java.io.OutputStream outStream) Encodes the given value of type T onto the given output stream.
protected long	getEncodedElementByteSize(java.lang.Void value) Returns the size in bytes of the encoded value using this coder.
TypeDescriptor<java.lang.Void>	getEncodedTypeDescriptor() Returns the TypeDescriptor for the type encoded.
boolean	isRegisterByteSizeObserverCheap(java.lang.Void value) Returns whether Coder.registerByteSizeObserver(T, org.apache.beam.sdk.util.common.ElementByteSizeObserver) 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).
static VoidCoder	of()
java.lang.Object	structuralValue(java.lang.Void value) Returns an object with an Object.equals() method that represents structural equality on the argument.
void	verifyDeterministic() Throw Coder.NonDeterministicException if the coding is not deterministic.

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

equals, getCoderArguments, getComponents, hashCode

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

toString

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

consistentWithEquals, decode, encode, registerByteSizeObserver, verifyDeterministic, verifyDeterministic

Methods inherited from class java.lang.Object

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

Method Detail

of

public static VoidCoder of()

encode

public void encode(java.lang.Void value,
                   java.io.OutputStream outStream)

Description copied from class: Coder

Encodes the given value of type T onto the given output stream. Multiple elements can be encoded next to each other on the output stream, each coder should encode information to know how many bytes to read when decoding. A common approach is to prefix the encoding with the element's encoded length.

Specified by:

encode in class Coder<java.lang.Void>

decode

public @Nullable java.lang.Void decode(java.io.InputStream inStream)

Description copied from class: Coder

Decodes a value of type T from the given input stream in the given context. Returns the decoded value. Multiple elements can be encoded next to each other on the input stream, each coder should encode information to know how many bytes to read when decoding. A common approach is to prefix the encoding with the element's encoded length.

Specified by:

decode in class Coder<java.lang.Void>

verifyDeterministic

public void verifyDeterministic()

Description copied from class: AtomicCoder

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 that 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.

.

Unless overridden, does not throw. An AtomicCoder is presumed to be deterministic

Overrides:

verifyDeterministic in class AtomicCoder<java.lang.Void>

structuralValue

public java.lang.Object structuralValue(java.lang.Void 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(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.lang.Void>

isRegisterByteSizeObserverCheap

public boolean isRegisterByteSizeObserverCheap(java.lang.Void value)

Returns whether Coder.registerByteSizeObserver(T, org.apache.beam.sdk.util.common.ElementByteSizeObserver) 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.

By default, returns false. The default Coder.registerByteSizeObserver(T, org.apache.beam.sdk.util.common.ElementByteSizeObserver) implementation invokes Coder.getEncodedElementByteSize(T) which requires re-encoding an element unless it is overridden. This is considered expensive.

Overrides:

isRegisterByteSizeObserverCheap in class Coder<java.lang.Void>

Returns:

true. getEncodedElementByteSize(java.lang.Void) runs in constant time.

getEncodedTypeDescriptor

public TypeDescriptor<java.lang.Void> getEncodedTypeDescriptor()

Description copied from class: Coder

Returns the TypeDescriptor for the type encoded.

Overrides:

getEncodedTypeDescriptor in class Coder<java.lang.Void>

getEncodedElementByteSize

protected long getEncodedElementByteSize(java.lang.Void value)
                                  throws java.lang.Exception

Description copied from class: Coder

Returns the size in bytes of the encoded value using this coder.

Overrides:

getEncodedElementByteSize in class Coder<java.lang.Void>

Throws:

java.lang.Exception