org.apache.beam.sdk.io.hadoop

Class WritableCoder<T extends 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:

java.io.Serializable

public class WritableCoder<T extends 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:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	WritableCoder.WritableCoderProviderRegistrar A CoderProviderRegistrar which registers a CoderProvider which can handle writable types.

Nested classes/interfaces inherited from class org.apache.beam.sdk.coders.Coder

Coder.Context, Coder.NonDeterministicException

Constructor Summary

Constructors

Constructor and Description
WritableCoder(java.lang.Class<T> type)

Method Summary

Modifier and Type	Method and Description
T	decode(java.io.InputStream inStream) Decodes a value of type T from the given input stream in the given context.
void	encode(T value, java.io.OutputStream outStream) Encodes the given value of type T onto the given output stream.
boolean	equals(@Nullable java.lang.Object other)
java.util.List<Coder<?>>	getCoderArguments() 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.
static CoderProvider	getCoderProvider() Returns a CoderProvider which uses the WritableCoder for Hadoop writable types.
int	hashCode()
static <T extends Writable> WritableCoder<T>	of(java.lang.Class<T> clazz) Returns a WritableCoder instance for the provided element class.
void	verifyDeterministic() Throw Coder.NonDeterministicException if the coding is not deterministic.

Methods inherited from class org.apache.beam.sdk.coders.Coder

consistentWithEquals, decode, encode, getEncodedElementByteSize, getEncodedTypeDescriptor, isRegisterByteSizeObserverCheap, registerByteSizeObserver, structuralValue, verifyDeterministic, verifyDeterministic

Methods inherited from class java.lang.Object

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

Constructor Detail

WritableCoder

public WritableCoder(java.lang.Class<T> type)

Method Detail

of

public static <T extends Writable> WritableCoder<T> of(java.lang.Class<T> clazz)

Returns a WritableCoder instance for the provided element class.

Type Parameters:

T - the element type

encode

public void encode(T value,
                   java.io.OutputStream outStream)
            throws java.io.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 Writable>

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 T decode(java.io.InputStream inStream)
         throws java.io.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 Writable>

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<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 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 Writable>

Throws:

Coder.NonDeterministicException - if this coder is not deterministic.

equals

public boolean equals(@Nullable java.lang.Object other)

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

getCoderProvider

public static CoderProvider getCoderProvider()

Returns a CoderProvider which uses the WritableCoder for Hadoop writable types.

This method is invoked reflectively from DefaultCoder.