Package org.apache.beam.sdk.io.hadoop

Class WritableCoder<T extends org.apache.hadoop.io.Writable>

java.lang.Object
org.apache.beam.sdk.coders.Coder<T>
org.apache.beam.sdk.coders.CustomCoder<T>
org.apache.beam.sdk.io.hadoop.WritableCoder<T>
Type Parameters:
T - the type of elements handled by this coder.
All Implemented Interfaces:
Serializable
public class WritableCoder<T extends org.apache.hadoop.io.Writable> extends CustomCoder<T>
A WritableCoder is a Coder for a Java class that implements Writable.

To use, specify the coder type on a PCollection: 


 PCollection<MyRecord> records =
     foo.apply(...).setCoder(WritableCoder.of(MyRecord.class));
See Also:

  • Constructor Details

    • WritableCoder

      public WritableCoder(Class<T> type)

  • Method Details

    • of

      public static <T extends org.apache.hadoop.io.Writable> WritableCoder<T> of(Class<T> clazz)
      Returns a WritableCoder instance for the provided element class.
      Type Parameters:
      T - the element type

    • encode

      public void encode(T value, OutputStream outStream) throws IOException
      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<T extends org.apache.hadoop.io.Writable>
      Throws:
      IOException - if writing to the OutputStream fails for some reason

    • decode

      public T decode(InputStream inStream) throws IOException
      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<T extends org.apache.hadoop.io.Writable>
      Throws:
      IOException - if reading from the InputStream fails for some reason

    • getCoderArguments

      public List<Coder<?>> getCoderArguments()
      Description copied from class: CustomCoder
      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..

      Returns an empty list. A CustomCoder has no default argument coders.

      Overrides:
      getCoderArguments in class CustomCoder<T extends org.apache.hadoop.io.Writable>

    • verifyDeterministic

      public void verifyDeterministic() throws Coder.NonDeterministicException
      Description copied from class: CustomCoder
      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.
      Overrides:
      verifyDeterministic in class CustomCoder<T extends org.apache.hadoop.io.Writable>
      Throws:
      Coder.NonDeterministicException - a CustomCoder is presumed nondeterministic.

    • equals

      public boolean equals(@Nullable Object other)
      Overrides:
      equals in class Object

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • getCoderProvider

      public static CoderProvider getCoderProvider()
      Returns a CoderProvider which uses the WritableCoder for Hadoop writable types.

      This method is invoked reflectively from DefaultCoder.