Objects whose sole dependency is TypeLiteral

[kel...@gmail.com]

Suppose that you have a TypeLiteral analogue in some other library, which can be easily constructed from TypeLiteral via exporting TypeLiteral's getType() to the analogue's TypeLiteral.of() counterpart (or custom subclassing shenanigans).  Examples of this may include org.apache.commons.lang3.reflect.TypeLiteral (or the Typed interface...) or com.fasterxml.jackson.databind.TypeReference (though ultimately the goal is the non-generic JavaType...).  The common thing is that these objects have only one dependency, and that is on a TypeLiteral.  The question is that, given that the only dependency is TypeLiteral, is it possible to define a "broadly-applicable" binding, or will I be forced to enumerate types?  And when I mean "broadly-applicable", it could be either an automatic injection (similar to how TypeLiteral itself is injected) restricted to the types known by the injector, or "any type" including those that the injector does not (for example, via injector.getInstance(new TypeLiteral<Foobar>() {}), where Foobar was not used in the construction of the injector).

Also related: suppose in an assisted injection context TypeLiteral is your only unassisted dependency, like the following:

public interface TypedObjectFactory<T> {

    public TypedObject<T> build(T object);

}

public class TypedObject<T> {

    @Inject

    public TypedObject(TypeLiteral<T> type, @Assisted T object) { ... }

}

Is it possible to have a "broadly-applicable" installation (in this case, install FactoryModuleBuilder in broad terms like the above), or will I be forced to enumerate types?

[Sam Berlin]

You must enumerate your types.

sam

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[Tavian Barnes]

As long as JIT bindings are enabled, you can do something like this:

public class TypeTokenFactory<T> {

    @Inject TypeLiteral<T> typeLiteral;

    public TypeToken<T> create() {

        return (TypeToken<T>) TypeToken.of(typeLiteral.getType());
    }

}

Then you can inject a TypeTokenFactory<List<String>> or whatever.  But you can't make TypeToken<T> automatically injectable for all T.