com.google.cloud.dataflow.sdk.coders

Class MapCoder<K,V>

java.lang.Object

com.google.cloud.dataflow.sdk.coders.StandardCoder<T>

com.google.cloud.dataflow.sdk.coders.MapCoderBase<java.util.Map<K,V>>

com.google.cloud.dataflow.sdk.coders.MapCoder<K,V>

Type Parameters:

K - the type of the keys of the KVs being transcoded

V - the type of the values of the KVs being transcoded

All Implemented Interfaces:

Coder<java.util.Map<K,V>>, java.io.Serializable

public class MapCoder<K,V>
extends MapCoderBase<java.util.Map<K,V>>

A MapCoder encodes Maps.

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface com.google.cloud.dataflow.sdk.coders.Coder

Coder.Context, Coder.NonDeterministicException

Method Summary

Methods

Modifier and Type	Method and Description
java.util.Map<K,V>	decode(java.io.InputStream inStream, Coder.Context context) Decodes a value of type T from the given input stream in the given context.
void	encode(java.util.Map<K,V> map, java.io.OutputStream outStream, Coder.Context context) Encodes the given value of type T onto the given output stream in the given context.
java.util.List<? extends Coder<?>>	getCoderArguments() If this is a Coder for a parameterized type, returns the list of Coders being used for each of the parameters, or returns null if this cannot be done or this is not a parameterized type.
static <K,V> java.util.List<java.lang.Object>	getInstanceComponents(java.util.Map<K,V> exampleValue) Returns the key and value for an arbitrary element of this map, if it is non-empty, otherwise returns null.
Coder<K>	getKeyCoder()
Coder<V>	getValueCoder()
boolean	isDeterministic() Deprecated.
static <K,V> MapCoder<K,V>	of(Coder<K> keyCoder, Coder<V> valueCoder) Produces a MapCoder with the given keyCoder and valueCoder.
static MapCoder<?,?>	of(java.util.List<Coder<?>> components)
void	registerByteSizeObserver(java.util.Map<K,V> map, com.google.cloud.dataflow.sdk.util.common.ElementByteSizeObserver observer, Coder.Context context) Notifies ElementByteSizeObserver about the byte size of the encoded value using this coder.
void	verifyDeterministic() Throw Coder.NonDeterministicException if the coding is not deterministic.

Methods inherited from class com.google.cloud.dataflow.sdk.coders.MapCoderBase

of

Methods inherited from class com.google.cloud.dataflow.sdk.coders.StandardCoder

asCloudObject, equals, getComponents, getEncodedElementByteSize, hashCode, isRegisterByteSizeObserverCheap, toString, verifyDeterministic, verifyDeterministic

Methods inherited from class java.lang.Object

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

Method Detail

of

public static <K,V> MapCoder<K,V> of(Coder<K> keyCoder,
                     Coder<V> valueCoder)

Produces a MapCoder with the given keyCoder and valueCoder.

of

public static MapCoder<?,?> of(java.util.List<Coder<?>> components)

getInstanceComponents

public static <K,V> java.util.List<java.lang.Object> getInstanceComponents(java.util.Map<K,V> exampleValue)

Returns the key and value for an arbitrary element of this map, if it is non-empty, otherwise returns null.

getKeyCoder

public Coder<K> getKeyCoder()

getValueCoder

public Coder<V> getValueCoder()

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 interface: Coder

Encodes the given value of type T onto the given output stream in the given context.

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.Map<K,V> decode(java.io.InputStream inStream,
                        Coder.Context context)
                          throws java.io.IOException,
                                 CoderException

Description copied from interface: Coder

Decodes a value of type T from the given input stream in the given context. Returns the decoded value.

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<? extends Coder<?>> getCoderArguments()

Description copied from interface: Coder

If this is a Coder for a parameterized type, returns the list of Coders being used for each of the parameters, or returns null if this cannot be done or this is not a parameterized type.

isDeterministic

@Deprecated
public boolean isDeterministic()

Deprecated.

Not all maps have a deterministic encoding.

For example, HashMap comparison does not depend on element order, so two HashMap instances may be equal but produce different encodings.

verifyDeterministic

public void verifyDeterministic()
                         throws Coder.NonDeterministicException

Description copied from interface: Coder

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 which 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 interface Coder<java.util.Map<K,V>>

Overrides:

verifyDeterministic in class StandardCoder<java.util.Map<K,V>>

Throws:

Coder.NonDeterministicException - if this coder is not deterministic.

registerByteSizeObserver

public void registerByteSizeObserver(java.util.Map<K,V> map,
                            com.google.cloud.dataflow.sdk.util.common.ElementByteSizeObserver observer,
                            Coder.Context context)
                              throws java.lang.Exception

Notifies ElementByteSizeObserver about the byte size of the encoded value using this coder.

Specified by:

registerByteSizeObserver in interface Coder<java.util.Map<K,V>>

Overrides:

registerByteSizeObserver in class StandardCoder<java.util.Map<K,V>>

Throws:

java.lang.Exception