Guice "Throwing Providers" : How to bind to a type with generics?

Question

Using Guice 3.0, I try to inject a Provider that can throw specific checked exceptions. So I use the Throwing Providers extension.

I created an interface for the Provider :

public interface IMyProvider<T> extends CheckedProvider<T> 
{
    @Override
    T get() throws MyException;
}

And its implementation :

public class MyProvider implements IMyProvider<List<SomeType>> 
{
    @Override
    public List<SomeType> get() throws MyException                        
    {
        //...
    }
}

I use the @Inject annotation on the object where I want to inject the Provider :

@Inject
public SomeConstructor(IMyProvider<List<SomeType>> myProvider)
{
    //...
}

Now, my problem is : how to bind this Provider?

Since generics are used, I though about using TypeLiteral :

bind(MyProvider.class);
ThrowingProviderBinder.create(binder())
                      .bind(IMyProvider.class, new TypeLiteral<List<SomeType>>(){})
                      .to(MyProvider.class);

But it seems TypeLiteral is not a valid argument for this bind() method.

Am I missing something?

UPDATE :

I found a workaround. By creating a class that extends ArrayList<SomeType>, I'm able to bind the Provider :

public class SomeTypeList extends ArrayList<SomeType>

and

bind(MyProvider.class);
ThrowingProviderBinder.create(binder())
                      .bind(IMyProvider.class, SomeTypeList.class)
                      .to(MyProvider.class);

But it would be easier if that SomeTypeList class wouldn't be required!

Answer 1

You're looking for a Type instance, which TypeLiteral does not natively implement.

I haven't worked with this directly, but Guice does provide a Types class, and there is also a method TypeLiteral.getType. Try one of the following:

• Types.listOf(SomeType.class)
• Types.newParameterizedType(List.class, SomeType.class)
• (new TypeLiteral<List<SomeType>>() {}).getType()

My preference is the first, which would look like this:

ThrowingProviderBinder
    .create(binder())
    .bind(IMyProvider.class, Types.listOf(SomeType.class))
    .to(MyProvider.class);