MapCoder (Google Cloud Dataflow SDK 1.9.1 API)

Google Cloud Dataflow SDK for Java, version 1.9.1

Warning: Dataflow SDK 1.x for Java is unsupported as of October 16, 2018. After August 12, 2020, you can use unsupported SDKs temporarily while you upgrade your pipelines. For more information, see Using an unsupported SDK.

For information on migrating from the 1.x SDK, see Migrating from Dataflow SDK 1.x for Java.

Note: If you are using Cloud Dataflow SDK version 2.x, see the Apache Beam API reference documentation.

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<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<Map<K,V>>, Serializable

  ---

  
  

  public class MapCoder<K,V>
  extends MapCoderBase<Map<K,V>>

  A Coder for Maps that encodes them according to provided coders for keys and values.

  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

    All Methods Static Methods Instance Methods Concrete Methods 

    Modifier and Type	Method and Description
    Map<K,V>	decode(InputStream inStream, Coder.Context context) Decodes a value of type T from the given input stream in the given context.
    void	encode(Map<K,V> map, OutputStream outStream, Coder.Context context) Encodes the given value of type T onto the given output stream in the given context.
    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> List<Object>	getInstanceComponents(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()
    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(List<Coder<?>> components)
    void	registerByteSizeObserver(Map<K,V> map, com.google.cloud.dataflow.sdk.util.common.ElementByteSizeObserver observer, Coder.Context context) Notifies the 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, consistentWithEquals, equals, getAllowedEncodings, getComponents, getEncodedElementByteSize, getEncodingId, hashCode, isRegisterByteSizeObserverCheap, structuralValue, 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(List<Coder<?>> components)

    • getInstanceComponents

      public static <K,V> List<Object> getInstanceComponents(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(Map<K,V> map,
                         OutputStream outStream,
                         Coder.Context context)
                  throws IOException,
                         CoderException

      Description copied from interface: Coder
      Encodes the given value of type T onto the given output stream in the given context.

      Throws:

      IOException - if writing to the OutputStream fails for some reason

      CoderException - if the value could not be encoded for some reason

    • decode

      public Map<K,V> decode(InputStream inStream,
                             Coder.Context context)
                      throws 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:

      IOException - if reading from the InputStream fails for some reason

      CoderException - if the value could not be decoded for some reason

    • getCoderArguments

      public 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.

      Returns:

      a List containing the key coder at index 0 at the and value coder at index 1.

    • verifyDeterministic

      public void verifyDeterministic()
                               throws Coder.NonDeterministicException

      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.

      Throws:

      NonDeterministicException - always. 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.

      Coder.NonDeterministicException - if this coder is not deterministic.

    • registerByteSizeObserver

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

      Description copied from class: StandardCoder
      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.

      For StandardCoder subclasses, this notifies observer about the byte size of the encoded value using this coder as returned by StandardCoder.getEncodedElementByteSize(T, com.google.cloud.dataflow.sdk.coders.Coder.Context).

      Specified by:

      registerByteSizeObserver in interface Coder<Map<K,V>>

      Overrides:

      registerByteSizeObserver in class StandardCoder<Map<K,V>>

      Throws:

      Exception