TypeDescriptor (Apache Beam 2.59.0)

java.lang.Object
- org.apache.beam.sdk.values.TypeDescriptor<T>

Type Parameters:

T - the type represented by this TypeDescriptor

All Implemented Interfaces:

java.io.Serializable
```
public abstract class TypeDescriptor<T>
extends java.lang.Object
implements java.io.Serializable
```
A description of a Java type, including actual generic parameters where possible.
To prevent losing actual type arguments due to erasure, create an anonymous subclass with concrete types:
```
 TypeDescriptor<List<String>> typeDescriptor = new TypeDescriptor<List<String>>() {};
 
```
If the above were not an anonymous subclass, the type List<String> would be erased and unavailable at run time.
See Also:

Serialized Form

Constructor Summary

Constructors
Modifier	Constructor and Description
`protected`	`TypeDescriptor()` Creates a `TypeDescriptor` representing the type parameter `T`.
`protected`	`TypeDescriptor(java.lang.Class<?> clazz)` Creates a `TypeDescriptor` representing the type parameter `T`, which should resolve to a concrete type in the context of the class `clazz`.
`protected`	`TypeDescriptor(java.lang.Object instance)` Creates a `TypeDescriptor` representing the type parameter `T`, which should resolve to a concrete type in the context of the class `clazz`.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`boolean`	`equals(@Nullable java.lang.Object other)` Two type descriptor are equal if and only if they represent the same type.
`java.util.List<TypeDescriptor<?>>`	`getArgumentTypes(java.lang.reflect.Method method)` Returns a list of argument types for the given method, which must be a part of the class.
`java.lang.Iterable<TypeDescriptor>`	`getClasses()` Returns a set of `TypeDescriptor`s, one for each superclass (including this class).
`@Nullable TypeDescriptor<?>`	`getComponentType()` Returns the component type if this type is an array type, otherwise returns `null`.
`java.lang.Iterable<TypeDescriptor>`	`getInterfaces()` Returns a set of `TypeDescriptor`s, one for each interface implemented by this class.
`java.lang.Class<? super T>`	`getRawType()` Returns the `Class` underlying the `Type` represented by this `TypeDescriptor`.
`TypeDescriptor<? super T>`	`getSupertype(java.lang.Class<? super T> superclass)` Returns the generic form of a supertype.
`java.lang.reflect.Type`	`getType()` Returns the `Type` represented by this `TypeDescriptor`.
`java.lang.reflect.TypeVariable<java.lang.Class<? super T>>`	`getTypeParameter(java.lang.String paramName)` Returns a `TypeVariable` for the named type parameter.
`java.lang.Iterable<TypeDescriptor>`	`getTypes()` Returns a set of `TypeDescriptor`, one for each superclass as well as each interface implemented by this class.
`int`	`hashCode()`
`boolean`	`hasUnresolvedParameters()` Returns whether this `TypeDescriptor` has any unresolved type parameters, as opposed to being a concrete type.
`boolean`	`isArray()` Returns true if this type is known to be an array type.
`boolean`	`isSubtypeOf(TypeDescriptor<?> parent)` Return true if this type is a subtype of the given type.
`boolean`	`isSupertypeOf(TypeDescriptor<?> source)` Returns true if this type is assignable from the given type.
`static <T> TypeDescriptor<T>`	`of(java.lang.Class<T> type)` Returns a `TypeDescriptor` representing the given type.
`static TypeDescriptor<?>`	`of(java.lang.reflect.Type type)` Returns a `TypeDescriptor` representing the given type.
`TypeDescriptor<?>`	`resolveType(java.lang.reflect.Type type)` Returns a `TypeDescriptor` representing the given type, with type variables resolved according to the specialization in this type.
`java.lang.String`	`toString()`
`<X> TypeDescriptor<T>`	`where(TypeParameter<X> typeParameter, TypeDescriptor<X> typeDescriptor)` Returns a new `TypeDescriptor` where the type variable represented by `typeParameter` are substituted by `type`.
`TypeDescriptor<T>`	`where(java.lang.reflect.Type formal, java.lang.reflect.Type actual)` A more general form of `where(TypeParameter, TypeDescriptor)` that returns a new `TypeDescriptor` by matching `formal` against `actual` to resolve type variables in the current `TypeDescriptor`.

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

- Constructor Detail
  - TypeDescriptor
```
protected TypeDescriptor()
```
    Creates a TypeDescriptor representing the type parameter T. To use this constructor properly, the type parameter must be a concrete type, for example new TypeDescriptor<List<String>>(){}.
  - TypeDescriptor
```
protected TypeDescriptor(java.lang.Object instance)
```
    Creates a TypeDescriptor representing the type parameter T, which should resolve to a concrete type in the context of the class clazz.
    Unlike TypeDescriptor(Class) this will also use context's of the enclosing instances while attempting to resolve the type. This means that the types of any classes instantiated in the concrete instance should be resolvable.
  - TypeDescriptor
```
protected TypeDescriptor(java.lang.Class<?> clazz)
```
    Creates a TypeDescriptor representing the type parameter T, which should resolve to a concrete type in the context of the class clazz.
- Method Detail
  - of
```
public static <T> TypeDescriptor<T> of(java.lang.Class<T> type)
```
    Returns a TypeDescriptor representing the given type.
  - of
```
public static TypeDescriptor<?> of(java.lang.reflect.Type type)
```
    Returns a TypeDescriptor representing the given type.
  - getType
```
public java.lang.reflect.Type getType()
```
    Returns the Type represented by this TypeDescriptor.
  - getRawType
```
public java.lang.Class<? super T> getRawType()
```
    Returns the Class underlying the Type represented by this TypeDescriptor.
  - getComponentType
```
public @Nullable TypeDescriptor<?> getComponentType()
```
    Returns the component type if this type is an array type, otherwise returns null.
  - getSupertype
```
public final TypeDescriptor<? super T> getSupertype(java.lang.Class<? super T> superclass)
```
    Returns the generic form of a supertype.
  - isArray
```
public final boolean isArray()
```
    Returns true if this type is known to be an array type.
  - getTypeParameter
```
public final java.lang.reflect.TypeVariable<java.lang.Class<? super T>> getTypeParameter(java.lang.String paramName)
```
    Returns a TypeVariable for the named type parameter. Throws IllegalArgumentException if a type variable by the requested type parameter is not found.
    For example, new TypeDescriptor<List>(){}.getTypeParameter("T") returns a TypeVariable<? super List> representing the formal type parameter T.
    Do not mistake the type parameters (formal type argument list) with the actual type arguments. For example, if a class Foo extends List<String>, it does not make sense to ask for a type parameter, because Foo does not have any.
  - isSupertypeOf
```
public final boolean isSupertypeOf(TypeDescriptor<?> source)
```
    Returns true if this type is assignable from the given type.
  - isSubtypeOf
```
public final boolean isSubtypeOf(TypeDescriptor<?> parent)
```
    Return true if this type is a subtype of the given type.
  - getArgumentTypes
```
public java.util.List<TypeDescriptor<?>> getArgumentTypes(java.lang.reflect.Method method)
```
    Returns a list of argument types for the given method, which must be a part of the class.
  - resolveType
```
public TypeDescriptor<?> resolveType(java.lang.reflect.Type type)
```
    Returns a TypeDescriptor representing the given type, with type variables resolved according to the specialization in this type.
    For example, consider the following class:
```
 class MyList implements List<String> { ... }
 
```
    The TypeDescriptor returned by
```
 TypeDescriptor.of(MyList.class)
     .resolveType(Mylist.class.getMethod("get", int.class).getGenericReturnType)
 
```
    will represent the type String.
  - getTypes
```
public java.lang.Iterable<TypeDescriptor> getTypes()
```
    Returns a set of TypeDescriptor, one for each superclass as well as each interface implemented by this class.
  - getInterfaces
```
public java.lang.Iterable<TypeDescriptor> getInterfaces()
```
    Returns a set of TypeDescriptors, one for each interface implemented by this class.
  - getClasses
```
public java.lang.Iterable<TypeDescriptor> getClasses()
```
    Returns a set of TypeDescriptors, one for each superclass (including this class).
  - where
```
public <X> TypeDescriptor<T> where(TypeParameter<X> typeParameter,
                                   TypeDescriptor<X> typeDescriptor)
```
    Returns a new TypeDescriptor where the type variable represented by typeParameter are substituted by type. For example, it can be used to construct Map<K, V> for any K and V type:
```
 static <K, V> TypeDescriptor<Map<K, V>> mapOf(
     TypeDescriptor<K> keyType, TypeDescriptor<V> valueType) {
   return new TypeDescriptor<Map<K, V>>() {}
       .where(new TypeParameter<K>() {}, keyType)
       .where(new TypeParameter<V>() {}, valueType);
 }
 
```
    Type Parameters:
    
    X - The parameter type
    
    Parameters:
    
    typeParameter - the parameter type variable
    
    typeDescriptor - the actual type to substitute
  - where
```
public TypeDescriptor<T> where(java.lang.reflect.Type formal,
                               java.lang.reflect.Type actual)
```
    A more general form of where(TypeParameter, TypeDescriptor) that returns a new TypeDescriptor by matching formal against actual to resolve type variables in the current TypeDescriptor.
  - hasUnresolvedParameters
```
public boolean hasUnresolvedParameters()
```
    Returns whether this TypeDescriptor has any unresolved type parameters, as opposed to being a concrete type.
    For example:
```
 TypeDescriptor.of(new ArrayList<String>() {}.getClass()).hasUnresolvedTypeParameters()
   => false, because the anonymous class is instantiated with a concrete type

 class TestUtils {
   <T> ArrayList<T> createTypeErasedList() {
     return new ArrayList<T>() {};
   }
 }

 TypeDescriptor.of(TestUtils.<String>createTypeErasedList().getClass())
   => true, because the type variable T got type-erased and the anonymous ArrayList class
   is instantiated with an unresolved type variable T.
 
```
  - toString
```
public java.lang.String toString()
```
    Overrides:
    
    toString in class java.lang.Object
  - equals
```
public boolean equals(@Nullable java.lang.Object other)
```
    Two type descriptor are equal if and only if they represent the same type.
    
    Overrides:
    
    equals in class java.lang.Object
  - hashCode
```
public int hashCode()
```
    Overrides:
    
    hashCode in class java.lang.Object

Class TypeDescriptor<T>

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

TypeDescriptor

TypeDescriptor

TypeDescriptor

Method Detail

of

of

getType

getRawType

getComponentType

getSupertype

isArray

getTypeParameter

isSupertypeOf

isSubtypeOf

getArgumentTypes

resolveType

getTypes

getInterfaces

getClasses

where

where

hasUnresolvedParameters

toString

equals

hashCode