org.apache.commons.lang3.reflect

Class TypeLiteral<T>

java.lang.Object

org.apache.commons.lang3.reflect.TypeLiteral<T>

Type Parameters:

T - the type

All Implemented Interfaces:

Typed<T>

public abstract class TypeLiteral<T>
extends Object
implements Typed<T>

Type literal comparable to javax.enterprise.util.TypeLiteral, made generally available outside the JEE context. Allows the passing around of a "token" that represents a type in a typesafe manner, as opposed to passing the (non-parameterized) Type object itself. Consider:

You might see such a typesafe API as:

 class Typesafe {
   <T> T obtain(Class<T> type, ...);
 }
 

Consumed in the manner of:

 Foo foo = typesafe.obtain(Foo.class, ...);
 

Yet, you run into problems when you want to do this with a parameterized type:

 List<String> listOfString = typesafe.obtain(List.class, ...); // could only give us a raw List
 

java.lang.reflect.Type might provide some value:

 Type listOfStringType = ...; // firstly, how to obtain this? Doable, but not straightforward.
 List<String> listOfString = (List<String>) typesafe.obtain(listOfStringType, ...); // nongeneric Type would necessitate a cast
 

The "type literal" concept was introduced to provide an alternative, i.e.:

 class Typesafe {
   <T> T obtain(TypeLiteral<T> type, ...);
 }
 

Consuming code looks like:

 List<String> listOfString = typesafe.obtain(new TypeLiteral<List<String>>() {}, ...);
 

This has the effect of "jumping up" a level to tie a java.lang.reflect.Type to a type variable while simultaneously making it short work to obtain a Type instance for any given type, inline.

Additionally TypeLiteral implements the Typed interface which is a generalization of this concept, and which may be implemented in custom classes. It is suggested that APIs be defined in terms of the interface, in the following manner:

   <T> T obtain(Typed<T> typed, ...);
 

Since:

3.2

Field Summary

Fields

Modifier and Type	Field and Description
Type	value Represented type.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	TypeLiteral() The default constructor.

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object obj)
Type	getType() Gets the Type represented by this entity.
int	hashCode()
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

value

public final Type value

Represented type.

Constructor Detail

TypeLiteral

protected TypeLiteral()

The default constructor.

Method Detail

equals

public final boolean equals(Object obj)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object

getType

public Type getType()

Description copied from interface: Typed

Gets the Type represented by this entity.

Specified by:

getType in interface Typed<T>

Returns:

Type