TypeDescriptors

java.lang.Object
- org.apache.beam.sdk.values.TypeDescriptors

```
public class TypeDescriptors
extends java.lang.Object
```
A utility class for creating TypeDescriptor objects for different types, such as Java primitive types, containers and KVs of other TypeDescriptor objects, and extracting type variables of parameterized types (e.g. extracting the OutputT type variable of a DoFn<InputT, OutputT>).

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`static interface`	`TypeDescriptors.TypeVariableExtractor<InputT,OutputT>` A helper interface for use with `extractFromTypeParameters(Object, Class, TypeVariableExtractor)`.

Constructor Summary

Constructors
Constructor and Description

TypeDescriptors()

Constructors
Constructor and Description
`TypeDescriptors()`

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`static TypeDescriptor<java.math.BigDecimal>`	`bigdecimals()` The `TypeDescriptor` for BigDecimal.
`static TypeDescriptor<java.math.BigInteger>`	`bigintegers()` The `TypeDescriptor` for BigInteger.
`static TypeDescriptor<java.lang.Boolean>`	`booleans()` The `TypeDescriptor` for Boolean.
`static TypeDescriptor<java.lang.Byte>`	`bytes()` The `TypeDescriptor` for Byte.
`static TypeDescriptor<java.lang.Character>`	`characters()` The `TypeDescriptor` for Character.
`static TypeDescriptor<java.lang.Double>`	`doubles()` The `TypeDescriptor` for Double.
`static <T,V> TypeDescriptor<V>`	`extractFromTypeParameters(T instance, java.lang.Class<? super T> supertype, TypeDescriptors.TypeVariableExtractor<T,V> extractor)` Extracts a type from the actual type parameters of a parameterized class, subject to Java type erasure.
`static <T,V> TypeDescriptor<V>`	`extractFromTypeParameters(TypeDescriptor<T> type, java.lang.Class<? super T> supertype, TypeDescriptors.TypeVariableExtractor<T,V> extractor)` Like `extractFromTypeParameters(Object, Class, TypeVariableExtractor)`, but takes a `TypeDescriptor` of the instance being analyzed rather than the instance itself.
`static TypeDescriptor<java.lang.Float>`	`floats()` The `TypeDescriptor` for Float.
`static <InputT,OutputT> TypeDescriptor<InputT>`	`inputOf(SerializableFunction<InputT,OutputT> fn)` Returns a type descriptor for the input of the given `SerializableFunction`, subject to Java type erasure: returns `null` if the type was erased.
`static TypeDescriptor<java.lang.Integer>`	`integers()` The `TypeDescriptor` for Integer.
`static <T> TypeDescriptor<java.lang.Iterable<T>>`	`iterables(TypeDescriptor<T> iterable)` The `TypeDescriptor` for `Iterable`.
`static <K,V> TypeDescriptor<KV<K,V>>`	`kvs(TypeDescriptor<K> key, TypeDescriptor<V> value)` The `TypeDescriptor` for `KV`.
`static <T> TypeDescriptor<java.util.List<T>>`	`lists(TypeDescriptor<T> element)` The `TypeDescriptor` for `List`.
`static TypeDescriptor<java.lang.Long>`	`longs()` The `TypeDescriptor` for Long.
`static TypeDescriptor<java.lang.Void>`	`nulls()` The `TypeDescriptor` for nulls/Void.
`static <InputT,OutputT> TypeDescriptor<OutputT>`	`outputOf(SerializableFunction<InputT,OutputT> fn)` Returns a type descriptor for the output of the given `SerializableFunction`, subject to Java type erasure: returns `null` if the type was erased.
`static <T> TypeDescriptor<java.util.Set<T>>`	`sets(TypeDescriptor<T> element)` The `TypeDescriptor` for `Set`.
`static TypeDescriptor<java.lang.Short>`	`shorts()` The `TypeDescriptor` for Short.
`static TypeDescriptor<java.lang.String>`	`strings()` The `TypeDescriptor` for String.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail
- TypeDescriptors
```
public TypeDescriptors()
```

Method Detail

booleans

public static TypeDescriptor<java.lang.Boolean> booleans()

The TypeDescriptor for Boolean. This is the equivalent of:

 new TypeDescriptor<Boolean>() {};

Returns:: A TypeDescriptor for Boolean

doubles

public static TypeDescriptor<java.lang.Double> doubles()

The TypeDescriptor for Double. This is the equivalent of:

 new TypeDescriptor<Double>() {};

Returns:: A TypeDescriptor for Double

floats

public static TypeDescriptor<java.lang.Float> floats()

The TypeDescriptor for Float. This is the equivalent of:

 new TypeDescriptor<Float>() {};

Returns:: A TypeDescriptor for Float

integers

public static TypeDescriptor<java.lang.Integer> integers()

The TypeDescriptor for Integer. This is the equivalent of:

 new TypeDescriptor<Integer>() {};

Returns:: A TypeDescriptor for Integer

longs

public static TypeDescriptor<java.lang.Long> longs()

The TypeDescriptor for Long. This is the equivalent of:

 new TypeDescriptor<Long>() {};

Returns:: A TypeDescriptor for Long

shorts

public static TypeDescriptor<java.lang.Short> shorts()

The TypeDescriptor for Short. This is the equivalent of:

 new TypeDescriptor<Short>() {};

Returns:: A TypeDescriptor for Short

bigdecimals

public static TypeDescriptor<java.math.BigDecimal> bigdecimals()

The TypeDescriptor for BigDecimal. This is the equivalent of:

 new TypeDescriptor<BigDecimal>() {};

Returns:: A TypeDescriptor for BigDecimal

bigintegers

public static TypeDescriptor<java.math.BigInteger> bigintegers()

The TypeDescriptor for BigInteger. This is the equivalent of:

 new TypeDescriptor<BigInteger>() {};

Returns:: A TypeDescriptor for BigInteger

strings

public static TypeDescriptor<java.lang.String> strings()

The TypeDescriptor for String. This is the equivalent of:

 new TypeDescriptor<String>() {};

Returns:: A TypeDescriptor for String

characters

public static TypeDescriptor<java.lang.Character> characters()

The TypeDescriptor for Character. This is the equivalent of:

 new TypeDescriptor<Character>() {};

Returns:: A TypeDescriptor for Character

bytes

public static TypeDescriptor<java.lang.Byte> bytes()

The TypeDescriptor for Byte. This is the equivalent of:

 new TypeDescriptor<Byte>() {};

Returns:: A TypeDescriptor for Byte

nulls
```
public static TypeDescriptor<java.lang.Void> nulls()
```
The TypeDescriptor for nulls/Void. This is the equivalent of:
```
 new TypeDescriptor<Void>() {};
 
```
Returns:

A TypeDescriptor for nulls/Void

kvs

public static <K,V> TypeDescriptor<KV<K,V>> kvs(TypeDescriptor<K> key,
                                                TypeDescriptor<V> value)

The TypeDescriptor for KV. This is the equivalent of:

 new TypeDescriptor<KV<K,V>>() {};

Example of use:

 
 PCollection<String> words = ...;
 PCollection<KV<String, String>> words = words.apply(FlatMapElements
         .into(TypeDescriptors.kv(TypeDescriptors.strings(), TypeDescriptors.strings()))
         .via(...));

Parameters:: key - The TypeDescriptor for the key; value - The TypeDescriptor for the value
Returns:: A TypeDescriptor for KV

sets

public static <T> TypeDescriptor<java.util.Set<T>> sets(TypeDescriptor<T> element)

The TypeDescriptor for Set. This is the equivalent of:

 new TypeDescriptor<Set<E>>() {};

Example of use:

 
 PCollection<String> words = ...;
 PCollection<Set<String>> words = words.apply(FlatMapElements
         .into(TypeDescriptors.sets(TypeDescriptors.strings()))
         .via(...));

Parameters:: element - The TypeDescriptor for the set
Returns:: A TypeDescriptor for Set

lists

public static <T> TypeDescriptor<java.util.List<T>> lists(TypeDescriptor<T> element)

The TypeDescriptor for List. This is the equivalent of:

 new TypeDescriptor<List<E>>() {};

Example of use:

 
 PCollection<String> words = ...;
 PCollection<List<String>> words = words.apply(FlatMapElements
         .into(TypeDescriptors.lists(TypeDescriptors.strings()))
         .via(...));

Parameters:: element - The TypeDescriptor for the list
Returns:: A TypeDescriptor for List

iterables

public static <T> TypeDescriptor<java.lang.Iterable<T>> iterables(TypeDescriptor<T> iterable)

The TypeDescriptor for Iterable. This is the equivalent of:

 new TypeDescriptor<Iterable<E>>() {};

Example of use:

 
 PCollection<String> words = ...;
 PCollection<Iterable<String>> words = words.apply(FlatMapElements
         .into(TypeDescriptors.iterables(TypeDescriptors.strings()))
         .via(...));

Parameters:: iterable - The TypeDescriptor for the iterable
Returns:: A TypeDescriptor for Iterable

extractFromTypeParameters

@Nullable
public static <T,V> TypeDescriptor<V> extractFromTypeParameters(T instance,
                                                                          java.lang.Class<? super T> supertype,
                                                                          TypeDescriptors.TypeVariableExtractor<T,V> extractor)

Extracts a type from the actual type parameters of a parameterized class, subject to Java type erasure. The type to extract is specified in a way that is safe w.r.t. changing the type signature of the parameterized class, as opposed to specifying the name or index of a type variable.

Example of use:


   class Foo<BarT> {
     private SerializableFunction<BarT, String> fn;

     TypeDescriptor<BarT> inferBarTypeDescriptorFromFn() {
       return TypeDescriptors.extractFromTypeParameters(
         fn,
         SerializableFunction.class,
         // The actual type of "fn" is matched against the input type of the extractor,
         // and the obtained values of type variables of the superclass are substituted
         // into the output type of the extractor.
         new TypeVariableExtractor<SerializableFunction<BarT, String>, BarT>() {});
     }
   }

Parameters:: instance - The object being analyzed; supertype - Parameterized superclass of interest; extractor - A class for specifying the type to extract from the supertype
Returns:: A TypeDescriptor for the actual value of the result type of the extractor, or null if the type was erased.

extractFromTypeParameters

@Nullable
public static <T,V> TypeDescriptor<V> extractFromTypeParameters(TypeDescriptor<T> type,
                                                                          java.lang.Class<? super T> supertype,
                                                                          TypeDescriptors.TypeVariableExtractor<T,V> extractor)

Like extractFromTypeParameters(Object, Class, TypeVariableExtractor), but takes a TypeDescriptor of the instance being analyzed rather than the instance itself.

inputOf
```
@Nullable
public static <InputT,OutputT> TypeDescriptor<InputT> inputOf(SerializableFunction<InputT,OutputT> fn)
```
Returns a type descriptor for the input of the given SerializableFunction, subject to Java type erasure: returns null if the type was erased.

outputOf
```
@Nullable
public static <InputT,OutputT> TypeDescriptor<OutputT> outputOf(SerializableFunction<InputT,OutputT> fn)
```
Returns a type descriptor for the output of the given SerializableFunction, subject to Java type erasure: returns null if the type was erased.

Class TypeDescriptors

Nested Class Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

TypeDescriptors

Method Detail

booleans

doubles

floats

integers

longs

shorts

bigdecimals

bigintegers

strings

characters

bytes

nulls

kvs

sets

lists

iterables

extractFromTypeParameters

extractFromTypeParameters

inputOf

outputOf