org.apache.beam.sdk.values

Class TupleTag<V>

java.lang.Object

org.apache.beam.sdk.values.TupleTag<V>

Type Parameters:

V - the type of the elements or values of the tagged thing, e.g., a PCollection<V>.

All Implemented Interfaces:

java.io.Serializable

public class TupleTag<V>
extends java.lang.Object
implements java.io.Serializable

A TupleTag is a typed tag to use as the key of a heterogeneously typed tuple, like PCollectionTuple. Its generic type parameter allows tracking the static type of things stored in tuples.

To aid in assigning default Coders for results of a ParDo, an output TupleTag should be instantiated with an extra {} so it is an instance of an anonymous subclass without generic type parameters. Input TupleTags require no such extra instantiation (although it doesn't hurt). For example:

 TupleTag<SomeType> inputTag = new TupleTag<>();
 TupleTag<SomeOtherType> outputTag = new TupleTag<SomeOtherType>(){};
 

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
TupleTag() Constructs a new TupleTag, with a fresh unique id.
TupleTag(java.lang.String id) Constructs a new TupleTag with the given id.

Method Summary

Modifier and Type	Method and Description
boolean	equals(@Nullable java.lang.Object that)
java.lang.String	getId() Returns the id of this TupleTag.
java.lang.String	getOutName(int outIndex) If this TupleTag is tagging output outputIndex of a PTransform, returns the name that should be used by default for the output.
TypeDescriptor<V>	getTypeDescriptor() Returns a TypeDescriptor capturing what is known statically about the type of this TupleTag instance's most-derived class.
int	hashCode()
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

TupleTag

public TupleTag()

Constructs a new TupleTag, with a fresh unique id.

This is the normal way TupleTags are constructed.

TupleTag

public TupleTag(java.lang.String id)

Constructs a new TupleTag with the given id.

It is up to the user to ensure that two TupleTags with the same id actually mean the same tag and carry the same generic type parameter. Violating this invariant can lead to hard-to-diagnose runtime type errors. Consequently, this operation should be used very sparingly, such as when the producer and consumer of TupleTags are written in separate modules and can only coordinate via ids rather than shared TupleTag instances. Most of the time, TupleTag() should be preferred.

Method Detail

getId

public java.lang.String getId()

Returns the id of this TupleTag.

Two TupleTags with the same id are considered equal.

TupleTags are not ordered, i.e., the class does not implement Comparable interface. TupleTags implement equals and hashCode, making them suitable for use as keys in HashMap and HashSet.

getOutName

public java.lang.String getOutName(int outIndex)

If this TupleTag is tagging output outputIndex of a PTransform, returns the name that should be used by default for the output.

getTypeDescriptor

public TypeDescriptor<V> getTypeDescriptor()

Returns a TypeDescriptor capturing what is known statically about the type of this TupleTag instance's most-derived class.

This is useful for a TupleTag constructed as an instance of an anonymous subclass with a trailing {}, e.g., new TupleTag<SomeType>(){}.

equals

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

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object