OptionalCoder (Apache Beam 2.64.0)

java.lang.Object
- org.apache.beam.sdk.coders.Coder<T>
- - org.apache.beam.sdk.coders.StructuredCoder<java.util.Optional<T>>
  - - org.apache.beam.sdk.coders.OptionalCoder<T>

Type Parameters:

T - the type of the values being transcoded

All Implemented Interfaces:

java.io.Serializable
```
public class OptionalCoder<T>
extends StructuredCoder<java.util.Optional<T>>
```
A OptionalCoder encodes optional values of type T using a nested Coder<T>. OptionalCoder uses exactly 1 byte per entry to indicate whether the value is empty, then adds the encoding of the inner coder for non-empty values.

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

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`boolean`	`consistentWithEquals()` `OptionalCoder` is consistent with equals if the nested `Coder` is.
`java.util.Optional<T>`	`decode(java.io.InputStream inStream)` Decodes a value of type `T` from the given input stream in the given context.
`void`	`encode(java.util.Optional<T> value, java.io.OutputStream outStream)` Encodes the given value of type `T` onto the given output stream.
`java.util.List<Coder<T>>`	`getCoderArguments()` If this is a `Coder` for a parameterized type, returns the list of `Coder`s being used for each of the parameters in the same order they appear within the parameterized type's type signature.
`protected long`	`getEncodedElementByteSize(java.util.Optional<T> value)` Overridden to short-circuit the default `StructuredCoder` behavior of encoding and counting the bytes.
`TypeDescriptor<java.util.Optional<T>>`	`getEncodedTypeDescriptor()` Returns the `TypeDescriptor` for the type encoded.
`Coder<T>`	`getValueCoder()` Returns the inner `Coder` wrapped by this `OptionalCoder` instance.
`boolean`	`isRegisterByteSizeObserverCheap(java.util.Optional<T> value)` `OptionalCoder` is cheap if `valueCoder` is cheap.
`static <T> OptionalCoder<T>`	`of(Coder<T> valueCoder)`
`void`	`registerByteSizeObserver(java.util.Optional<T> value, org.apache.beam.sdk.util.common.ElementByteSizeObserver observer)` Overridden to short-circuit the default `StructuredCoder` behavior of encoding and counting the bytes.
`java.lang.Object`	`structuralValue(java.util.Optional<T> value)` Returns an object with an `Object.equals()` method that represents structural equality on the argument.
`void`	`verifyDeterministic()` `OptionalCoder` is deterministic if the nested `Coder` is.

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, getEncodedElementByteSizeUsingCoder, verifyDeterministic, verifyDeterministic

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Method Detail
  - of
```
public static <T> OptionalCoder<T> of(Coder<T> valueCoder)
```
  - getValueCoder
```
public Coder<T> getValueCoder()
```
    Returns the inner Coder wrapped by this OptionalCoder instance.
  - encode
```
public void encode(java.util.Optional<T> value,
                   java.io.OutputStream outStream)
            throws java.io.IOException,
                   CoderException
```
    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.util.Optional<T>>
    
    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
```
public java.util.Optional<T> decode(java.io.InputStream inStream)
                             throws java.io.IOException,
                                    CoderException
```
    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.util.Optional<T>>
    
    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
```
public java.util.List<Coder<T>> getCoderArguments()
```
    Description copied from class: Coder
    
    If this is a Coder for a parameterized type, returns the list of Coders being used for each of the parameters in the same order they appear within the parameterized type's type signature. If this cannot be done, or this Coder does not encode/decode a parameterized type, returns the empty list.
    
    Specified by:
    
    getCoderArguments in class Coder<java.util.Optional<T>>
  - verifyDeterministic
```
public void verifyDeterministic()
                         throws Coder.NonDeterministicException
```
    OptionalCoder is deterministic if the nested Coder is.
    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.
    Specified by:
    
    verifyDeterministic in class Coder<java.util.Optional<T>>
    
    Throws:
    
    Coder.NonDeterministicException - if this coder is not deterministic.
  - consistentWithEquals
```
public boolean consistentWithEquals()
```
    OptionalCoder is consistent with equals if the nested Coder is.
    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.Optional<T>>
  - structuralValue
```
public java.lang.Object structuralValue(java.util.Optional<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(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.Optional<T>>
  - registerByteSizeObserver
```
public void registerByteSizeObserver(java.util.Optional<T> value,
                                     org.apache.beam.sdk.util.common.ElementByteSizeObserver observer)
                              throws java.lang.Exception
```
    Overridden to short-circuit the default StructuredCoder behavior of encoding and counting the bytes. The size is known (1 byte) when value is null, otherwise the size is 1 byte plus the size of nested Coder's encoding of value.
    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.
    By default, this notifies observer about the byte size of the encoded value using this coder as returned by Coder.getEncodedElementByteSize(T).
    
    Overrides:
    
    registerByteSizeObserver in class Coder<java.util.Optional<T>>
    
    Throws:
    
    java.lang.Exception
  - getEncodedElementByteSize
```
protected long getEncodedElementByteSize(java.util.Optional<T> value)
                                  throws java.lang.Exception
```
    Overridden to short-circuit the default StructuredCoder behavior of encoding and counting the bytes. The size is known (1 byte) when value is null, otherwise the size is 1 byte plus the size of nested Coder's encoding of value.
    Returns the size in bytes of the encoded value using this coder.
    
    Overrides:
    
    getEncodedElementByteSize in class Coder<java.util.Optional<T>>
    
    Throws:
    
    java.lang.Exception
  - isRegisterByteSizeObserverCheap
```
public boolean isRegisterByteSizeObserverCheap(java.util.Optional<T> value)
```
    OptionalCoder is cheap if valueCoder is cheap.
    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.util.Optional<T>>
  - getEncodedTypeDescriptor
```
public TypeDescriptor<java.util.Optional<T>> getEncodedTypeDescriptor()
```
    Description copied from class: Coder
    
    Returns the TypeDescriptor for the type encoded.
    
    Overrides:
    
    getEncodedTypeDescriptor in class Coder<java.util.Optional<T>>

Class OptionalCoder<T>

Nested Class Summary

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

Method Summary

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

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

Methods inherited from class java.lang.Object

Method Detail

of

getValueCoder

encode

decode

getCoderArguments

verifyDeterministic

consistentWithEquals

structuralValue

registerByteSizeObserver

getEncodedElementByteSize

isRegisterByteSizeObserverCheap

getEncodedTypeDescriptor