Google Cloud Dataflow SDK for Java, version 1.9.1
Class NullableCoder<T>
- java.lang.Object
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- com.google.cloud.dataflow.sdk.coders.StandardCoder<T>
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- com.google.cloud.dataflow.sdk.coders.NullableCoder<T>
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- Type Parameters:
T
- the type of the values being transcoded
- All Implemented Interfaces:
- Coder<T>, Serializable
public class NullableCoder<T> extends StandardCoder<T>
ANullableCoder
encodes nullable values of typeT
using a nestedCoder<T>
that does not toleratenull
values.NullableCoder
uses exactly 1 byte per entry to indicate whether the value isnull
, then adds the encoding of the inner coder for non-null values.- See Also:
- Serialized Form
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Nested Class Summary
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Nested classes/interfaces inherited from interface com.google.cloud.dataflow.sdk.coders.Coder
Coder.Context, Coder.NonDeterministicException
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method and Description boolean
consistentWithEquals()
NullableCoder
is consistent with equals if the nestedCoder
is.T
decode(InputStream inStream, Coder.Context context)
Decodes a value of typeT
from the given input stream in the given context.void
encode(T value, OutputStream outStream, Coder.Context context)
Encodes the given value of typeT
onto the given output stream in the given context.List<Coder<T>>
getCoderArguments()
If this is aCoder
for a parameterized type, returns the list ofCoder
s being used for each of the parameters, or returnsnull
if this cannot be done or this is not a parameterized type.protected long
getEncodedElementByteSize(T value, Coder.Context context)
Overridden to short-circuit the defaultStandardCoder
behavior of encoding and counting the bytes.boolean
isRegisterByteSizeObserverCheap(T value, Coder.Context context)
NullableCoder
is cheap ifvalueCoder
is cheap.static <T> NullableCoder<T>
of(Coder<T> valueCoder)
static NullableCoder<?>
of(List<Coder<?>> components)
void
registerByteSizeObserver(T value, com.google.cloud.dataflow.sdk.util.common.ElementByteSizeObserver observer, Coder.Context context)
Overridden to short-circuit the defaultStandardCoder
behavior of encoding and counting the bytes.Object
structuralValue(T value)
Returns an object with anObject.equals()
method that represents structural equality on the argument.void
verifyDeterministic()
NullableCoder
is deterministic if the nestedCoder
is.-
Methods inherited from class com.google.cloud.dataflow.sdk.coders.StandardCoder
asCloudObject, equals, getAllowedEncodings, getComponents, getEncodingId, hashCode, toString, verifyDeterministic, verifyDeterministic
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Method Detail
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of
public static <T> NullableCoder<T> of(Coder<T> valueCoder)
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of
public static NullableCoder<?> of(List<Coder<?>> components)
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encode
public void encode(@Nullable T value, OutputStream outStream, Coder.Context context) throws IOException, CoderException
Description copied from interface:Coder
Encodes the given value of typeT
onto the given output stream in the given context.- Throws:
IOException
- if writing to theOutputStream
fails for some reasonCoderException
- if the value could not be encoded for some reason
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decode
@Nullable public T decode(InputStream inStream, Coder.Context context) throws IOException, CoderException
Description copied from interface:Coder
Decodes a value of typeT
from the given input stream in the given context. Returns the decoded value.- Throws:
IOException
- if reading from theInputStream
fails for some reasonCoderException
- if the value could not be decoded for some reason
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getCoderArguments
public List<Coder<T>> getCoderArguments()
Description copied from interface:Coder
If this is aCoder
for a parameterized type, returns the list ofCoder
s being used for each of the parameters, or returnsnull
if this cannot be done or this is not a parameterized type.
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verifyDeterministic
public void verifyDeterministic() throws Coder.NonDeterministicException
NullableCoder
is deterministic if the nestedCoder
is. ThrowCoder.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()
orComparable.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.
- two values that compare as equal (via
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consistentWithEquals
public boolean consistentWithEquals()
NullableCoder
is consistent with equals if the nestedCoder
is. Returnstrue
if thisCoder
is injective with respect toObject.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 fornull
.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.- Specified by:
consistentWithEquals
in interfaceCoder<T>
- Overrides:
consistentWithEquals
in classStandardCoder<T>
- Returns:
false
forStandardCoder
unless overridden.
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structuralValue
public Object structuralValue(@Nullable T value) throws Exception
Description copied from interface:Coder
Returns an object with anObject.equals()
method that represents structural equality on the argument.For any two values
x
andy
of typeT
, if their encoded bytes are the same, then it must be the case thatstructuralValue(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 anequals()
method, even if the input value isnull
.
See also
Coder.consistentWithEquals()
.- Specified by:
structuralValue
in interfaceCoder<T>
- Overrides:
structuralValue
in classStandardCoder<T>
- Throws:
Exception
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registerByteSizeObserver
public void registerByteSizeObserver(@Nullable T value, com.google.cloud.dataflow.sdk.util.common.ElementByteSizeObserver observer, Coder.Context context) throws Exception
Overridden to short-circuit the defaultStandardCoder
behavior of encoding and counting the bytes. The size is known (1 byte) whenvalue
isnull
, otherwise the size is 1 byte plus the size of nestedCoder
's encoding ofvalue
. Notifies theElementByteSizeObserver
about the byte size of the encoded value using thisCoder
.Not intended to be called by user code, but instead by
PipelineRunner
implementations.For
StandardCoder
subclasses, this notifiesobserver
about the byte size of the encoded value using this coder as returned byStandardCoder.getEncodedElementByteSize(T, com.google.cloud.dataflow.sdk.coders.Coder.Context)
.- Specified by:
registerByteSizeObserver
in interfaceCoder<T>
- Overrides:
registerByteSizeObserver
in classStandardCoder<T>
- Throws:
Exception
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getEncodedElementByteSize
protected long getEncodedElementByteSize(@Nullable T value, Coder.Context context) throws Exception
Overridden to short-circuit the defaultStandardCoder
behavior of encoding and counting the bytes. The size is known (1 byte) whenvalue
isnull
, otherwise the size is 1 byte plus the size of nestedCoder
's encoding ofvalue
. Returns the size in bytes of the encoded value using this coder.- Overrides:
getEncodedElementByteSize
in classStandardCoder<T>
- Throws:
Exception
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isRegisterByteSizeObserverCheap
public boolean isRegisterByteSizeObserverCheap(@Nullable T value, Coder.Context context)
NullableCoder
is cheap ifvalueCoder
is cheap. Returns whetherCoder.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 thisCoder
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.- Specified by:
isRegisterByteSizeObserverCheap
in interfaceCoder<T>
- Overrides:
isRegisterByteSizeObserverCheap
in classStandardCoder<T>
- Returns:
false
unless it is overridden.StandardCoder.registerByteSizeObserver(T, com.google.cloud.dataflow.sdk.util.common.ElementByteSizeObserver, com.google.cloud.dataflow.sdk.coders.Coder.Context)
invokesStandardCoder.getEncodedElementByteSize(T, com.google.cloud.dataflow.sdk.coders.Coder.Context)
which requires re-encoding an element unless it is overridden. This is considered expensive.
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