V
- the type of the elements or values of the tagged thing, e.g., a PCollection<V>
.public class TupleTag<V>
extends java.lang.Object
implements java.io.Serializable
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>(){};
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. |
Modifier and Type | Method and Description |
---|---|
boolean |
equals(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() |
public TupleTag()
TupleTag
, with a fresh unique id.
This is the normal way TupleTag
s are constructed.
public TupleTag(java.lang.String id)
TupleTag
with the given id.
It is up to the user to ensure that two TupleTag
s 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 TupleTag
s are written in separate
modules and can only coordinate via ids rather than shared TupleTag
instances. Most of
the time, TupleTag()
should be preferred.
public java.lang.String getId()
TupleTag
.
Two TupleTag
s with the same id are considered equal.
TupleTag
s 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.
public java.lang.String getOutName(int outIndex)
TupleTag
is tagging output outputIndex
of a PTransform
, returns
the name that should be used by default for the output.public TypeDescriptor<V> getTypeDescriptor()
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>(){}
.
public boolean equals(java.lang.Object that)
equals
in class java.lang.Object
public int hashCode()
hashCode
in class java.lang.Object
public java.lang.String toString()
toString
in class java.lang.Object