org.apache.beam.sdk.coders

Class StringDelegateCoder<T>

java.lang.Object

org.apache.beam.sdk.coders.Coder<T>

org.apache.beam.sdk.coders.CustomCoder<T>

org.apache.beam.sdk.coders.StringDelegateCoder<T>

Type Parameters:

T - The type of objects coded.

All Implemented Interfaces:

java.io.Serializable

public final class StringDelegateCoder<T>
extends CustomCoder<T>

A Coder that wraps a Coder<String> and encodes/decodes values via string representations.

To decode, the input byte stream is decoded to a String, and this is passed to the single-argument constructor for T.

To encode, the input value is converted via toString(), and this string is encoded.

In order for this to operate correctly for a class Clazz, it must be the case for any instance x that x.equals(new Clazz(x.toString())).

This method of encoding is not designed for ease of evolution of Clazz; it should only be used in cases where the class is stable or the encoding is not important. If evolution of the class is important, see AvroCoder or any other evolution safe encoding.

See Also:

Serialized Form

Nested Class Summary

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

Coder.Context, Coder.NonDeterministicException

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	StringDelegateCoder(java.lang.Class<T> clazz, TypeDescriptor<T> typeDescriptor)

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.
T	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(T value, java.io.OutputStream outStream) Encodes the given value of type T onto the given output stream.
void	encode(T value, java.io.OutputStream outStream, Coder.Context context) Encodes the given value of type T onto the given output stream in the given context.
boolean	equals(@Nullable java.lang.Object o)
TypeDescriptor<T>	getEncodedTypeDescriptor() Returns the TypeDescriptor for the type encoded.
int	hashCode()
static <T> StringDelegateCoder<T>	of(java.lang.Class<T> clazz)
static <T> StringDelegateCoder<T>	of(java.lang.Class<T> clazz, TypeDescriptor<T> typeDescriptor)
java.lang.Object	structuralValue(T value) Returns an object with an Object.equals() method that represents structural equality on the argument.
java.lang.String	toString()
void	verifyDeterministic() Throw Coder.NonDeterministicException if the coding is not deterministic.

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

getCoderArguments

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

consistentWithEquals, getEncodedElementByteSize, isRegisterByteSizeObserverCheap, registerByteSizeObserver, verifyDeterministic, verifyDeterministic

Methods inherited from class java.lang.Object

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

Constructor Detail

StringDelegateCoder

protected StringDelegateCoder(java.lang.Class<T> clazz,
                              TypeDescriptor<T> typeDescriptor)

Method Detail

of

public static <T> StringDelegateCoder<T> of(java.lang.Class<T> clazz)

of

public static <T> StringDelegateCoder<T> of(java.lang.Class<T> clazz,
                                            TypeDescriptor<T> typeDescriptor)

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

equals

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

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

encode

public void encode(T value,
                   java.io.OutputStream outStream)
            throws CoderException,
                   java.io.IOException

Description copied from class: Coder

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

Specified by:

encode in class Coder<T>

Throws:

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

java.io.IOException - if writing to the OutputStream fails for some reason

encode

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

Description copied from class: Coder

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

Overrides:

encode in class Coder<T>

Throws:

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

java.io.IOException - if writing to the OutputStream fails for some reason

decode

public T decode(java.io.InputStream inStream)
         throws CoderException,
                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.

Specified by:

decode in class Coder<T>

Throws:

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

java.io.IOException - if reading from the InputStream fails for some reason

decode

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

Overrides:

decode in class Coder<T>

Throws:

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

java.io.IOException - if reading from the InputStream fails for some reason

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>

Throws:

Coder.NonDeterministicException - if this coder is not deterministic.

structuralValue

public java.lang.Object structuralValue(T value)

Description copied from class: 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(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().

By default, if this coder is Coder.consistentWithEquals(), and the value is not null, returns the provided object. Otherwise, encodes the value into a byte[], and returns an object that performs array equality on the encoded bytes.

Overrides:

structuralValue in class Coder<T>

getEncodedTypeDescriptor

public TypeDescriptor<T> getEncodedTypeDescriptor()

Description copied from class: Coder

Returns the TypeDescriptor for the type encoded.

Overrides:

getEncodedTypeDescriptor in class Coder<T>