com.google.cloud.dataflow.sdk.coders

Class DelegateCoder<T,IntermediateT>

java.lang.Object

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

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

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

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

com.google.cloud.dataflow.sdk.coders.DelegateCoder<T,IntermediateT>

Type Parameters:

T - The type of objects coded by this Coder.

IntermediateT - The type of objects a T will be converted to for coding.

All Implemented Interfaces:

Coder<T>, Serializable

Direct Known Subclasses:

StringDelegateCoder

public class DelegateCoder<T,IntermediateT>
extends CustomCoder<T>

A DelegateCoder<T, IntermediateT> wraps a Coder for IntermediateT and encodes/decodes values of type Ts by converting to/from IntermediateT and then encoding/decoding using the underlying Coder<IntermediateT>.

The conversions from T to IntermediateT and vice versa must be supplied as DelegateCoder.CodingFunction, a serializable function that may throw any Exception. If a thrown exception is an instance of CoderException or IOException, it will be re-thrown, otherwise it will be wrapped as a CoderException.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	DelegateCoder.CodingFunction<InputT,OutputT> A CodingFunction<InputT, OutputT> is a serializable function from InputT to OutputT that may throw any Exception.

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

Coder.Context, Coder.NonDeterministicException

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	DelegateCoder(Coder<IntermediateT> coder, DelegateCoder.CodingFunction<T,IntermediateT> toFn, DelegateCoder.CodingFunction<IntermediateT,T> fromFn)

Method Summary

Modifier and Type	Method and Description
T	decode(InputStream inStream, Coder.Context context) Decodes a value of type T from the given input stream in the given context.
void	encode(T value, OutputStream outStream, Coder.Context context) Encodes the given value of type T onto the given output stream in the given context.
Collection<String>	getAllowedEncodings() A collection of encodings supported by Coder.decode(java.io.InputStream, com.google.cloud.dataflow.sdk.coders.Coder.Context) in addition to the value of StandardCoder.getEncodingId().
Coder<IntermediateT>	getCoder() Returns the coder used to encode/decode the intermediate values produced/consumed by the coding functions of this DelegateCoder.
String	getEncodingId() The encoding id for the binary format of the delegate coder is a combination of the underlying coder class and its encoding id.
static <T,IntermediateT> DelegateCoder<T,IntermediateT>	of(Coder<IntermediateT> coder, DelegateCoder.CodingFunction<T,IntermediateT> toFn, DelegateCoder.CodingFunction<IntermediateT,T> fromFn)
Object	structuralValue(T value) Returns an object with an Object.equals() method that represents structural equality on the argument.
String	toString()
void	verifyDeterministic() A delegate coder is deterministic if the underlying coder is deterministic.

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

asCloudObject, of

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

getCoderArguments, getInstanceComponents

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

consistentWithEquals, equals, getComponents, getEncodedElementByteSize, hashCode, isRegisterByteSizeObserverCheap, registerByteSizeObserver, verifyDeterministic, verifyDeterministic

Methods inherited from class java.lang.Object

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

Constructor Detail

DelegateCoder

protected DelegateCoder(Coder<IntermediateT> coder,
                        DelegateCoder.CodingFunction<T,IntermediateT> toFn,
                        DelegateCoder.CodingFunction<IntermediateT,T> fromFn)

Method Detail

of

public static <T,IntermediateT> DelegateCoder<T,IntermediateT> of(Coder<IntermediateT> coder,
                                                                  DelegateCoder.CodingFunction<T,IntermediateT> toFn,
                                                                  DelegateCoder.CodingFunction<IntermediateT,T> fromFn)

encode

public void encode(T value,
                   OutputStream outStream,
                   Coder.Context context)
            throws CoderException,
                   IOException

Description copied from interface: Coder

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

Throws:

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

IOException - if writing to the OutputStream fails for some reason

decode

public T decode(InputStream inStream,
                Coder.Context context)
         throws CoderException,
                IOException

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:

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

IOException - if reading from the InputStream fails for some reason

getCoder

public Coder<IntermediateT> getCoder()

Returns the coder used to encode/decode the intermediate values produced/consumed by the coding functions of this DelegateCoder.

verifyDeterministic

public void verifyDeterministic()
                         throws Coder.NonDeterministicException

A delegate coder is deterministic if the underlying coder is deterministic. For this to be safe, the intermediate CodingFunction<T, IntermediateT> must also be deterministic.

Specified by:

verifyDeterministic in interface Coder<T>

Overrides:

verifyDeterministic in class CustomCoder<T>

Throws:

Coder.NonDeterministicException - if this coder is not deterministic.

structuralValue

public Object structuralValue(T value)
                       throws Exception

Description copied from interface: Coder

Returns an object with an Object.equals() method that represents structural equality on the argument.

For any two values x and y of type T, if their encoded bytes are the same, then it must be the case that structuralValue(x).equals(@code 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 an equals() method, even if the input value is null.

See also Coder.consistentWithEquals().

Specified by:

structuralValue in interface Coder<T>

Overrides:

structuralValue in class StandardCoder<T>

Throws:

Exception

toString

public String toString()

Overrides:

toString in class StandardCoder<T>

getEncodingId

public String getEncodingId()

The encoding id for the binary format of the delegate coder is a combination of the underlying coder class and its encoding id.

Note that this omits any description of the coding functions. These should be modified with care.

Specified by:

getEncodingId in interface Coder<T>

Overrides:

getEncodingId in class CustomCoder<T>

See Also:

StandardCoder.getAllowedEncodings()

getAllowedEncodings

public Collection<String> getAllowedEncodings()

Description copied from class: StandardCoder

A collection of encodings supported by Coder.decode(java.io.InputStream, com.google.cloud.dataflow.sdk.coders.Coder.Context) in addition to the value of StandardCoder.getEncodingId().

By default, this is empty.

Specified by:

getAllowedEncodings in interface Coder<T>

Overrides:

getAllowedEncodings in class StandardCoder<T>

See Also:

StandardCoder.getEncodingId()