public abstract class TypeLiteral<T> extends java.lang.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 castThe "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, ...);
| Modifier and Type | Field and Description |
|---|---|
java.lang.reflect.Type |
value
Represented type.
|
| Modifier | Constructor and Description |
|---|---|
protected |
TypeLiteral()
The default constructor.
|
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