Package org.apache.commons.lang3.reflect

Class 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