Class MapCoder<K,V>
- java.lang.Object
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- org.apache.beam.sdk.coders.Coder<T>
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- org.apache.beam.sdk.coders.StructuredCoder<java.util.Map<K,V>>
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- org.apache.beam.sdk.coders.MapCoder<K,V>
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- Type Parameters:
K
- the type of the keys of the KVs being transcodedV
- the type of the values of the KVs being transcoded
- All Implemented Interfaces:
java.io.Serializable
public class MapCoder<K,V> extends StructuredCoder<java.util.Map<K,V>>
ACoder
forMaps
that encodes them according to provided coders for keys and values.- See Also:
- Serialized Form
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Nested Class Summary
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Nested classes/interfaces inherited from class org.apache.beam.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 Description boolean
consistentWithEquals()
java.util.Map<K,V>
decode(java.io.InputStream inStream)
Decodes a value of typeT
from the given input stream in the given context.java.util.Map<K,V>
decode(java.io.InputStream inStream, Coder.Context context)
Decodes a value of typeT
from the given input stream in the given context.void
encode(java.util.Map<K,V> map, java.io.OutputStream outStream)
Encodes the given value of typeT
onto the given output stream.void
encode(java.util.Map<K,V> map, java.io.OutputStream outStream, Coder.Context context)
Encodes the given value of typeT
onto the given output stream in the given context.java.util.List<? extends Coder<?>>
getCoderArguments()
TypeDescriptor<java.util.Map<K,V>>
getEncodedTypeDescriptor()
Returns theTypeDescriptor
for the type encoded.Coder<K>
getKeyCoder()
Coder<V>
getValueCoder()
static <K,V>
MapCoder<K,V>of(Coder<K> keyCoder, Coder<V> valueCoder)
Produces a MapCoder with the given keyCoder and valueCoder.void
registerByteSizeObserver(java.util.Map<K,V> map, ElementByteSizeObserver observer)
Notifies theElementByteSizeObserver
about the byte size of the encoded value using thisCoder
.java.lang.Object
structuralValue(java.util.Map<K,V> value)
Returns an object with anObject.equals()
method that represents structural equality on the argument.void
verifyDeterministic()
ThrowCoder.NonDeterministicException
if the coding is not deterministic.-
Methods inherited from class org.apache.beam.sdk.coders.StructuredCoder
equals, getComponents, hashCode, toString
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Methods inherited from class org.apache.beam.sdk.coders.Coder
getEncodedElementByteSize, isRegisterByteSizeObserverCheap, verifyDeterministic, verifyDeterministic
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Method Detail
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of
public static <K,V> MapCoder<K,V> of(Coder<K> keyCoder, Coder<V> valueCoder)
Produces a MapCoder with the given keyCoder and valueCoder.
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encode
public void encode(java.util.Map<K,V> map, java.io.OutputStream outStream) throws java.io.IOException, CoderException
Description copied from class:Coder
Encodes the given value of typeT
onto the given output stream.- Specified by:
encode
in classCoder<java.util.Map<K,V>>
- Throws:
java.io.IOException
- if writing to theOutputStream
fails for some reasonCoderException
- if the value could not be encoded for some reason
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encode
public void encode(java.util.Map<K,V> map, java.io.OutputStream outStream, Coder.Context context) throws java.io.IOException, CoderException
Description copied from class:Coder
Encodes the given value of typeT
onto the given output stream in the given context.- Overrides:
encode
in classCoder<java.util.Map<K,V>>
- Throws:
java.io.IOException
- if writing to theOutputStream
fails for some reasonCoderException
- if the value could not be encoded for some reason
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decode
public java.util.Map<K,V> decode(java.io.InputStream inStream) throws java.io.IOException, CoderException
Description copied from class:Coder
Decodes a value of typeT
from the given input stream in the given context. Returns the decoded value.- Specified by:
decode
in classCoder<java.util.Map<K,V>>
- Throws:
java.io.IOException
- if reading from theInputStream
fails for some reasonCoderException
- if the value could not be decoded for some reason
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decode
public java.util.Map<K,V> decode(java.io.InputStream inStream, Coder.Context context) throws java.io.IOException, CoderException
Description copied from class:Coder
Decodes a value of typeT
from the given input stream in the given context. Returns the decoded value.- Overrides:
decode
in classCoder<java.util.Map<K,V>>
- Throws:
java.io.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 java.util.List<? extends Coder<?>> getCoderArguments()
If this is aCoder
for a parameterized type, returns the list ofCoder
s 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 thisCoder
does not encode/decode a parameterized type, returns the empty list.- Specified by:
getCoderArguments
in classCoder<java.util.Map<K,V>>
- Returns:
- a
List
containing the key coder at index 0 at the and value coder at index 1.
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verifyDeterministic
public void verifyDeterministic() throws Coder.NonDeterministicException
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.
- Specified by:
verifyDeterministic
in classCoder<java.util.Map<K,V>>
- Throws:
Coder.NonDeterministicException
- always. Not all maps have a deterministic encoding. For example,HashMap
comparison does not depend on element order, so twoHashMap
instances may be equal but produce different encodings.
- two values that compare as equal (via
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consistentWithEquals
public boolean consistentWithEquals()
Description copied from class:Coder
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.By default, returns false.
- Overrides:
consistentWithEquals
in classCoder<java.util.Map<K,V>>
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structuralValue
public java.lang.Object structuralValue(java.util.Map<K,V> value)
Description copied from class: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(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()
.By default, if this coder is
Coder.consistentWithEquals()
, and the value is not null, returns the provided object. Otherwise, encodes the value into abyte[]
, and returns an object that performs array equality on the encoded bytes.- Overrides:
structuralValue
in classCoder<java.util.Map<K,V>>
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registerByteSizeObserver
public void registerByteSizeObserver(java.util.Map<K,V> map, ElementByteSizeObserver observer) throws java.lang.Exception
Description copied from class:Coder
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.By default, this notifies
observer
about the byte size of the encoded value using this coder as returned byCoder.getEncodedElementByteSize(T)
.- Overrides:
registerByteSizeObserver
in classCoder<java.util.Map<K,V>>
- Throws:
java.lang.Exception
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getEncodedTypeDescriptor
public TypeDescriptor<java.util.Map<K,V>> getEncodedTypeDescriptor()
Description copied from class:Coder
Returns theTypeDescriptor
for the type encoded.- Overrides:
getEncodedTypeDescriptor
in classCoder<java.util.Map<K,V>>
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