org.apache.beam.sdk.extensions.protobuf

Class ProtoCoder<T extends com.google.protobuf.Message>

java.lang.Object

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

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

org.apache.beam.sdk.extensions.protobuf.ProtoCoder<T>

Type Parameters:

T - the Protocol Buffers Message handled by this Coder.

All Implemented Interfaces:

java.io.Serializable

Direct Known Subclasses:

DynamicProtoCoder

public class ProtoCoder<T extends com.google.protobuf.Message>
extends CustomCoder<T>

A Coder using Google Protocol Buffers binary format. ProtoCoder supports both Protocol Buffers syntax versions 2 and 3.

To learn more about Protocol Buffers, visit: https://developers.google.com/protocol-buffers

ProtoCoder is registered in the global CoderRegistry as the default Coder for any Message object. Custom message extensions are also supported, but these extensions must be registered for a particular ProtoCoder instance and that instance must be registered on the PCollection that needs the extensions:

 import MyProtoFile;
 import MyProtoFile.MyMessage;

 Coder<MyMessage> coder = ProtoCoder.of(MyMessage.class).withExtensionsFrom(MyProtoFile.class);
 PCollection<MyMessage> records = input.apply(...).setCoder(coder);
 

Versioning

ProtoCoder supports both versions 2 and 3 of the Protocol Buffers syntax. However, the Java runtime version of the google.com.protobuf library must match exactly the version of protoc that was used to produce the JAR files containing the compiled .proto messages.

For more information, see the Protocol Buffers documentation.

ProtoCoder and Determinism

In general, Protocol Buffers messages can be encoded deterministically within a single pipeline as long as:

• The encoded messages (and any transitively linked messages) do not use map fields.
• Every Java VM that encodes or decodes the messages use the same runtime version of the Protocol Buffers library and the same compiled .proto file JAR.

ProtoCoder and Encoding Stability

When changing Protocol Buffers messages, follow the rules in the Protocol Buffers language guides for proto2 and proto3 syntaxes, depending on your message type. Following these guidelines will ensure that the old encoded data can be read by new versions of the code.

Generally, any change to the message type, registered extensions, runtime library, or compiled proto JARs may change the encoding. Thus even if both the original and updated messages can be encoded deterministically within a single job, these deterministic encodings may not be the same across jobs.

See Also:

Serialized Form

Nested Class Summary

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

Coder.Context, Coder.NonDeterministicException

Field Summary

Fields

Modifier and Type	Field and Description
static long	serialVersionUID

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	ProtoCoder(java.lang.Class<T> protoMessageClass, java.util.Set<java.lang.Class<?>> extensionHostClasses) Private constructor.

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 other)
static CoderProvider	getCoderProvider() Returns a CoderProvider which uses the ProtoCoder for proto messages.
java.util.Set<java.lang.Class<?>>	getExtensionHosts()
com.google.protobuf.ExtensionRegistry	getExtensionRegistry() Returns the ExtensionRegistry listing all known Protocol Buffers extension messages to T registered with this ProtoCoder.
java.lang.Class<T>	getMessageType() Returns the Protocol Buffers Message type this ProtoCoder supports.
protected com.google.protobuf.Parser<T>	getParser() Get the memoized Parser, possibly initializing it lazily.
int	hashCode()
static <T extends com.google.protobuf.Message> ProtoCoder<T>	of(java.lang.Class<T> protoMessageClass) Returns a ProtoCoder for the given Protocol Buffers Message.
static <T extends com.google.protobuf.Message> ProtoCoder<T>	of(TypeDescriptor<T> protoMessageType) Returns a ProtoCoder for the Protocol Buffers Message indicated by the given TypeDescriptor.
void	verifyDeterministic() Throw Coder.NonDeterministicException if the coding is not deterministic.
ProtoCoder<T>	withExtensionsFrom(java.lang.Class<?>... moreExtensionHosts) See withExtensionsFrom(Iterable).
ProtoCoder<T>	withExtensionsFrom(java.lang.Iterable<java.lang.Class<?>> moreExtensionHosts) Returns a ProtoCoder like this one, but with the extensions from the given classes registered.

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

getCoderArguments

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

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

Methods inherited from class java.lang.Object

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

Field Detail

serialVersionUID

public static final long serialVersionUID

See Also:

Constant Field Values

Constructor Detail

ProtoCoder

protected ProtoCoder(java.lang.Class<T> protoMessageClass,
                     java.util.Set<java.lang.Class<?>> extensionHostClasses)

Private constructor.

Method Detail

of

public static <T extends com.google.protobuf.Message> ProtoCoder<T> of(java.lang.Class<T> protoMessageClass)

Returns a ProtoCoder for the given Protocol Buffers Message.

of

public static <T extends com.google.protobuf.Message> ProtoCoder<T> of(TypeDescriptor<T> protoMessageType)

Returns a ProtoCoder for the Protocol Buffers Message indicated by the given TypeDescriptor.

withExtensionsFrom

public ProtoCoder<T> withExtensionsFrom(java.lang.Iterable<java.lang.Class<?>> moreExtensionHosts)

Returns a ProtoCoder like this one, but with the extensions from the given classes registered.

Each of the extension host classes must be an class automatically generated by the Protocol Buffers compiler, protoc, that contains messages.

Does not modify this object.

withExtensionsFrom

public ProtoCoder<T> withExtensionsFrom(java.lang.Class<?>... moreExtensionHosts)

See withExtensionsFrom(Iterable).

Does not modify this object.

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 com.google.protobuf.Message>

Throws:

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

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

encode

public void encode(T value,
                   java.io.OutputStream outStream,
                   Coder.Context context)
            throws 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 extends com.google.protobuf.Message>

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 com.google.protobuf.Message>

Throws:

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

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

decode

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

Overrides:

decode in class Coder<T extends com.google.protobuf.Message>

Throws:

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

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

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

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 com.google.protobuf.Message>

Throws:

Coder.NonDeterministicException - if this coder is not deterministic.

getMessageType

public java.lang.Class<T> getMessageType()

Returns the Protocol Buffers Message type this ProtoCoder supports.

getExtensionHosts

public java.util.Set<java.lang.Class<?>> getExtensionHosts()

getExtensionRegistry

public com.google.protobuf.ExtensionRegistry getExtensionRegistry()

Returns the ExtensionRegistry listing all known Protocol Buffers extension messages to T registered with this ProtoCoder.

getParser

protected com.google.protobuf.Parser<T> getParser()

Get the memoized Parser, possibly initializing it lazily.

getCoderProvider

public static CoderProvider getCoderProvider()

Returns a CoderProvider which uses the ProtoCoder for proto messages.

This method is invoked reflectively from DefaultCoder.